- Introduction
- 1. Getting Started
- 2. Features
- 3. Configuration Overview
- 4. Serialization
- 5. Setting Up Client Network
- 6. Securing Client Connection
- 7. Using Node.js Client with Hazelcast IMDG
- 8. Development and Testing
- 9. Getting Help
- 10. Contributing
- 11. License
- 12. Copyright
This document provides information about the Node.js client for Hazelcast. This client uses Hazelcast's Open Client Protocol and works with Hazelcast IMDG 3.6 and higher versions.
See the following for more information on Node.js and Hazelcast IMDG:
- Hazelcast IMDG website
- Hazelcast IMDG Reference Manual
- About Node.js
See the Releases page of this repository.
This chapter provides information on how to get started with your Hazelcast Node.js client. It outlines the requirements, installation and configuration of the client, setting up a cluster, and provides a simple application that uses a distributed map in Node.js client.
- Windows, Linux or MacOS
- Node.js 4 or newer
- Java 6 or newer
- Hazelcast IMDG 3.6 or newer
- Latest Hazelcast Node.js client
Hazelcast Node.js client requires a working Hazelcast IMDG cluster to run. This cluster handles storage and manipulation of the user data. Clients are a way to connect to the Hazelcast IMDG cluster and access such data.
Hazelcast IMDG cluster consists of one or more cluster members. These members generally run on multiple virtual or physical machines and are connected to each other via network. Any data put on the cluster is partitioned to multiple members transparent to the user. It is therefore very easy to scale the system by adding new members as the data grows. Hazelcast IMDG cluster also offers resilience. Should any hardware or software problem causes a crash to any member, the data on that member is recovered from backups and the cluster continues to operate without any downtime. Hazelcast clients are an easy way to connect to a Hazelcast IMDG cluster and perform tasks on distributed data structures that live on the cluster.
In order to use Hazelcast Node.js client, we first need to setup a Hazelcast IMDG cluster.
There are following options to start a Hazelcast IMDG cluster easily:
- You can run standalone members by downloading and running JAR files from the website.
- You can embed members to your Java projects. The easiest way is to use hazelcast-member tool if you have brew installed in your computer.
We are going to download JARs from the website and run a standalone member for this guide.
Follow the instructions below to create a Hazelcast IMDG cluster:
- Go to Hazelcast's download page and download either the
.zipor.tardistribution of Hazelcast IMDG. - Decompress the contents into any directory that you want to run members from.
- Change into the directory that you decompressed the Hazelcast content and then into the
bindirectory. - Use either
start.shorstart.batdepending on your operating system. Once you run the start script, you should see the Hazelcast IMDG logs in the terminal.
You should see a log similar to the following, which means that your 1-member cluster is ready to be used:
INFO: [192.168.0.3]:5701 [dev] [3.10.4]
Members {size:1, ver:1} [
Member [192.168.0.3]:5701 - 65dac4d1-2559-44bb-ba2e-ca41c56eedd6 this
]
Sep 06, 2018 10:50:23 AM com.hazelcast.core.LifecycleService
INFO: [192.168.0.3]:5701 [dev] [3.10.4] [192.168.0.3]:5701 is STARTED
When you want to use features such as querying and language interoperability, you might need to add your own Java classes to the Hazelcast member in order to use them from your Node.js client. This can be done by adding your own compiled code to the CLASSPATH. To do this, compile your code with the CLASSPATH and add the compiled files to the user-lib directory in the extracted hazelcast-<version>.zip (or tar). Then, you can start your Hazelcast member by using the start scripts in the bin directory. The start scripts will automatically add your compiled classes to the CLASSPATH.
Note that if you are adding an IdentifiedDataSerializable or a Portable class, you need to add its factory too. Then, you should configure the factory in the hazelcast.xml configuration file. This file resides in the bin directory where you extracted the hazelcast-<version>.zip (or tar).
The following is an example configuration when you are adding an IdentifiedDataSerializable class:
<hazelcast>
...
<serialization>
<data-serializable-factories>
<data-serializable-factory factory-id=<identified-factory-id>>
IdentifiedFactoryClassName
</data-serializable-factory>
</data-serializable-factories>
</serialization>
...
</hazelcast>If you want to add a Portable class, you should use <portable-factories> instead of <data-serializable-factories> in the above configuration.
hazelcast-member is a tool to download and run Hazelcast IMDG members easily. If you have brew installed, run the following commands to instal this tool:
brew tap hazelcast/homebrew-hazelcast
brew install hazelcast-member
Now, you can start a member by running the following command:
hazelcast-member start
To stop a member, run the following command:
hazelcast-member stop
You can find more information about the hazelcast-member tool at its GitHub repo.
See the Hazelcast IMDG Reference Manual for more information on setting up the clusters.
Hazelcast Node.js client is on NPM. Just add hazelcast-client as a dependency to your Node.js project and you are good to go.
npm install hazelcast-client --save
If you are using Hazelcast IMDG and Node.js Client on the same computer, generally the default configuration should be fine. This is great for trying out the client. However, if you run the client on a different computer than any of the cluster members, you may need to do some simple configurations such as specifying the member addresses.
The Hazelcast IMDG members and clients have their own configuration options. You may need to reflect some of the member side configurations on the client side to properly connect to the cluster.
This section describes the most common configuration elements to get you started in no time. It discusses some member side configuration options to ease the understanding of Hazelcast's ecosystem. Then, the client side configuration options regarding the cluster connection are discussed. The configurations for the Hazelcast IMDG data structures that can be used in the Node.js client are discussed in the following sections.
See the Hazelcast IMDG Reference Manual and Configuration Overview section for more information.
Hazelcast IMDG aims to run out-of-the-box for most common scenarios. However if you have limitations on your network such as multicast being disabled, you may have to configure your Hazelcast IMDG members so that they can find each other on the network. Also, since most of the distributed data structures are configurable, you may want to configure them according to your needs. We will show you the basics about network configuration here.
There are two ways to configure Hazelcast IMDG:
- Using the
hazelcast.xmlconfiguration file. - Programmatically configuring the member before starting it from the Java code.
Since we use standalone servers, we will use the hazelcast.xml file to configure our cluster members.
When you download and unzip hazelcast-<version>.zip (or tar), you see the hazelcast.xml in the bin directory. When a Hazelcast member starts, it looks for the hazelcast.xml file to load the configuration from. A sample hazelcast.xml is shown below.
<hazelcast>
<group>
<name>dev</name>
<password>dev-pass</password>
</group>
<network>
<port auto-increment="true" port-count="100">5701</port>
<join>
<multicast enabled="true">
<multicast-group>224.2.2.3</multicast-group>
<multicast-port>54327</multicast-port>
</multicast>
<tcp-ip enabled="false">
<interface>127.0.0.1</interface>
<member-list>
<member>127.0.0.1</member>
</member-list>
</tcp-ip>
</join>
<ssl enabled="false"/>
</network>
<partition-group enabled="false"/>
<map name="default">
<backup-count>1</backup-count>
</map>
</hazelcast>We will go over some important configuration elements in the rest of this section.
<group>: Specifies which cluster this member belongs to. A member connects only to the other members that are in the same group as itself. As shown in the above configuration sample, there are<name>and<password>tags under the<group>element with some pre-configured values. You may give your clusters different names so that they can live in the same network without disturbing each other. Note that the cluster name should be the same across all members and clients that belong to the same cluster. The<password>tag is not in use since Hazelcast 3.9. It is there for backward compatibility purposes. You can remove or leave it as it is if you use Hazelcast 3.9 or later.<network><port>: Specifies the port number to be used by the member when it starts. Its default value is 5701. You can specify another port number, and if you setauto-incrementtotrue, then Hazelcast will try the subsequent ports until it finds an available port or theport-countis reached.<join>: Specifies the strategies to be used by the member to find other cluster members. Choose which strategy you want to use by setting itsenabledattribute totrueand the others tofalse.<multicast>: Members find each other by sending multicast requests to the specified address and port. It is very useful if IP addresses of the members are not static.<tcp>: This strategy uses a pre-configured list of known members to find an already existing cluster. It is enough for a member to find only one cluster member to connect to the cluster. The rest of the member list is automatically retrieved from that member. We recommend putting multiple known member addresses there to avoid disconnectivity should one of the members in the list is unavailable at the time of connection.
These configuration elements are enough for most connection scenarios. Now we will move onto the configuration of the Node.js client.
There are two ways to configure a Hazelcast Node.js client:
- Programmatically
- Declaratively (JSON)
This section describes some network configuration settings to cover common use cases in connecting the client to a cluster. See the Configuration Overview section and the following sections for information about detailed network configurations and/or additional features of Hazelcast Node.js client configuration.
An easy way to configure your Hazelcast Node.js client is to create a ClientConfig object and set the appropriate options. Then you can
supply this object to your client at the startup. This is the programmatic configuration approach. Another way to configure your client, which is the declarative approach, is to provide a hazelcast-client.json file. This is similar to the hazelcast.xml approach
in configuring the member. Note that hazelcast-client.json is a JSON file whereas the member configuration is XML based. Although these
two formats are different, you will realize that the names of configuration parameters are the same for both the client and member.
It is done this way to make it easier to transfer Hazelcast skills to multiple platforms.
Once you embedded hazelcast-client to your Node.js project, you may follow any of programmatic or declarative configuration approaches.
We will provide both ways for each configuration option in this section. Pick one way and stick to it.
Programmatic configuration
You need to create a ClientConfig object and adjust its properties. Then you can pass this object to the client when starting it.
let Client = require('hazelcast-client').Client;
let Config = require('hazelcast-client').Config;
let config = new Config.ClientConfig();
Client.newHazelcastClient(config).then(function(client) {
// some operations
});Declarative configuration
Hazelcast Node.js client looks for a hazelcast-client.json in the current working directory unless you provide a configuration object
at the startup. If you intend to configure your client using a configuration file, then place a hazelcast-client.json in the directory
of your application's entry point.
If you prefer to keep your hazelcast-client.json file somewhere else, you can override the environment variable HAZELCAST_CLIENT_CONFIG
with the location of your config file. In this case, the client uses the configuration file specified in the environment variable.
For the structure of hazelcast-client.json, see the hazelcast-client-full.json file. You
can use only the relevant parts of the file in your hazelcast-client.json and remove the rest. The default configuration is used for any
part that you do not explicitly set in the hazelcast-client.json file.
If you run the Hazelcast IMDG members in a different server than the client, you most probably have configured the members' ports and cluster names as explained in the previous section. If you did, then you need to make certain changes to the network settings of your client.
Programmatic:
let cfg = new Config.ClientConfig();
cfg.group.name = //group name of you clusterDeclarative:
{
"group": {
"name": "group name of you cluster"
}
}NOTE: If you have a Hazelcast IMDG release older than 3.11, you need to provide also a group password along with the group name.
You need to provide the IP address and port of at least one member in your cluster so the client can find it.
Programmatic:
let cfg = new Config.ClientConfig();
cfg.network.addresses.push('some-ip-address:port');Declarative:
{
"network": {
"clusterMembers": [
"some-ip-address:port"
],
}
}Now that we have a working cluster and we know how to configure both our cluster and client, we can run a simple program to use a distributed map in the Node.js client.
The following example first creates a programmatic configuration object. Then, it starts a client.
let Client = require('hazelcast-client').Client;
let Config = require('hazelcast-client').Config;
let config = new Config.ClientConfig(); // We create a config for illustrative purposes.
// We do not adjust this config. Therefore it has default settings.
Client.newHazelcastClient(config).then(function(client) {
console.log(client.getLocalEndpoint()); // Connects and prints some information about this client
});This should print logs about the cluster members and information about the client itself such as the client type, UUID and address.
[DefaultLogger] INFO at ConnectionAuthenticator: Connection to 192.168.0.3:5701 authenticated
[DefaultLogger] INFO at ClusterService: Members received.
[ Member {
address: Address { host: '192.168.0.3', port: 5701, type: 4 },
uuid: '05db1504-4f23-426b-9e8a-c9db587ad0d6',
isLiteMember: false,
attributes: {} } ]
[DefaultLogger] INFO at HazelcastClient: Client started
ClientInfo {
type: 'NodeJS',
uuid: '532e8479-2b86-47f9-a0fb-a2da13a8d584',
localAddress: Address { host: '127.0.0.1', port: 51903, type: 4 } }
Congratulations! You just started a Hazelcast Node.js client.
Using a Map
Let's manipulate a distributed map on a cluster using the client.
Save the following file as IT.js and run it using node IT.js.
IT.js
let Client = require('hazelcast-client').Client;
let Config = require('hazelcast-client').Config;
let config = new Config.ClientConfig();
Client.newHazelcastClient(config).then(function (client) {
var personnelMap;
return client.getMap('personnelMap').then(function (mp) {
personnelMap = mp;
return personnelMap.put('Alice', 'IT');
}).then(function () {
return personnelMap.put('Bob', 'IT');
}).then(function () {
return personnelMap.put('Clark', 'IT');
}).then(function () {
console.log("Added IT personnel. Logging all known personnel");
return personnelMap.entrySet();
}).then(function (allPersonnel) {
allPersonnel.forEach(function (person) {
console.log(person[0] + ' is in ' + person[1] + ' department');
});
return client.shutdown();
});
});Output
[DefaultLogger] INFO at HazelcastClient: Client started
Added IT personnel. Logging all known personnel
Alice is in IT department
Clark is in IT department
Bob is in IT department
You see this example puts all the IT personnel into a cluster-wide personnelMap and then prints all the known personnel.
Now create a Sales.js file as shown below and run it using node Sales.js.
Sales.js
let Client = require('hazelcast-client').Client;
let Config = require('hazelcast-client').Config;
let config = new Config.ClientConfig();
Client.newHazelcastClient(config).then(function (client) {
var personnelMap;
return client.getMap('personnelMap').then(function (mp) {
personnelMap = mp;
return personnelMap.put('Denise', 'Sales');
}).then(function () {
return personnelMap.put('Erwing', 'Sales');
}).then(function () {
return personnelMap.put('Faith', 'Sales');
}).then(function () {
console.log("Added Sales personnel. Logging all known personnel");
return personnelMap.entrySet();
}).then(function (allPersonnel) {
allPersonnel.forEach(function (person) {
console.log(person[0] + ' is in ' + person[1] + ' department');
});
return client.shutdown();
});
});Output
[DefaultLogger] INFO at HazelcastClient: Client started
Added Sales personnel. Logging all known personnel
Denise is in Sales department
Erwing is in Sales department
Faith is in Sales department
Alice is in IT department
Clark is in IT department
Bob is in IT department
You will see this time we add only the sales employees but we get the list all known employees including the ones in IT. That is because our map lives in the cluster and no matter which client we use, we can access the whole map.
See the Hazelcast Node.js code samples for more examples.
You can also see the Hazelcast Node.js API Documentation.
Hazelcast Node.js client supports the following data structures and features:
- Map
- Queue
- Set
- List
- MultiMap
- Replicated Map
- Ringbuffer
- Reliable Topic
- Lock
- Semaphore
- Atomic Long
- CRDT PN Counter
- Flake Id Generator
- Event Listeners
- Entry Processor
- Query (Predicates)
- Paging Predicate
- Built-in Predicates
- Listener with Predicate
- Fast Aggregations
- Near Cache Support
- Eventual Consistency Control
- Declarative Configuration (JSON)
- Programmatic Configuration
- Client Configuration Import
- Fail Fast on Invalid Configuration
- SSL Support (requires Enterprise server)
- Mutual Authentication (requires Enterprise server)
- Authorization
- Smart Client
- Unisocket Client
- Lifecycle Service
- Hazelcast Cloud Discovery
- IdentifiedDataSerializable Serialization
- Portable Serialization
- Custom Serialization
- Global Serialization
This chapter describes the options to configure your Node.js client and explains how you can import multiple configurations and how you should set paths and exported names for the client to load objects.
You can configure the Hazelcast Node.js client declaratively (JSON) or programmatically (API).
For programmatic configuration of the Hazelcast Node.js client, just instantiate a ClientConfig object and configure the
desired aspects. An example is shown below.
var Config = require('hazelcast-client').Config;
var cfg = new Config.ClientConfig();
cfg.networkConfig.addresses.push('127.0.0.1:5701');
return HazelcastClient.newHazelcastClient(cfg);See the ClientConfig class documentation at Hazelcast Node.js Client API Docs for details.
If the client is not supplied with a programmatic configuration at the time of initialization, it will look for a configuration file named hazelcast-client.json. If this file exists, then the configuration is loaded from it. Otherwise, the client will start with the default configuration. The following are the places that the client looks for a hazelcast-client.json in the given order:
- Environment variable: The client first looks for the environment variable
HAZELCAST_CLIENT_CONFIG. If it exists, the client looks for the configuration file in the specified location. - Current working directory: If there is no environment variable set, the client tries to load
hazelcast-client.jsonfrom the current working directory. - Default configuration: If all of the above methods fail, the client starts with the default configuration.
The default configuration is programmatic. If you want to override the default configuration declaratively, you need to create
a
hazelcast-client.jsonfile in your working directory. If you want to have an example for this file, you can findhazelcast-client-default.jsonandhazelcast-client-sample.jsonfiles in the GitHub repository.
Following is a sample JSON configuration file:
{
"group": {
"name": "hazel",
"password": "cast"
},
"properties": {
"hazelcast.client.heartbeat.timeout": 10000,
"hazelcast.client.invocation.retry.pause.millis": 4000,
"hazelcast.client.invocation.timeout.millis": 180000,
"hazelcast.invalidation.reconciliation.interval.seconds": 50,
"hazelcast.invalidation.max.tolerated.miss.count": 15,
"hazelcast.invalidation.min.reconciliation.interval.seconds": 60
},
"network": {
"clusterMembers": [
"127.0.0.1:5701"
],
"smartRouting": true,
"connectionTimeout": 6000,
"connectionAttemptPeriod": 4000,
"connectionAttemptLimit": 3
}
}In the following chapters you will learn the description of all elements included in a JSON configuration file used to configure Hazelcast Node.js client.
You can compose the declarative configuration of your Node.js client from multiple declarative
configuration snippets. In order to compose a declarative configuration, you can use the import element to load
different declarative configuration files.
Let's assume you have the following two configurations:
group-config.json:
{
"group": {
"name": "hazel",
"password": "cast"
}
}network-config.json:
{
"network": {
"clusterMembers": [
"127.0.0.10:4001",
"127.0.0.11:4001"
]
}
}To get your example client configuration out of the above two, use the import element as
shown below.
{
"import": [
"group-config.json",
"network-config.json"
]
}Note: Use
importelement on top level of JSON hierarchy.
For configuration elements that require you to specify a code piece, you will need to specify the path to the code and name of the exported element that you want the client to use. This configuration is set as follows:
{
"path": "path/to/file",
"exportedName": "MyObject"
}In the above configuration, path shows the address to the file that you want the client to load. Unless this is an
absolute path, it is relative to the location of hazelcast-config.json file.
In Javascript, you can define and export as many objects as you want in a single file. Above configuration element
is designed to load only one specified object from a file (MyObject). Therefore, exportedName specifies the name of desired object.
Let's say your project's directory structure is as follows:
my_app/
my_app/index.js
my_app/factory_utils.js
my_app/hazelcast-client.json
my_app/node_modules/
my_app/node_modules/hazelcast-client
In the factory_utils.js file, you have multiple exported functions:
exports.utilityFunction = function() {...}
exports.MySSLFactory = function() {...}In order to load MySSLFactory in your SSL configuration, you should set path and exportedName as factory_utils.js
and MySSLFactory, respectively.
If you have only one export as the default export from factory_utils.js, just skip the exportedName property and
the client will load the default export from the file.
Serialization is the process of converting an object into a stream of bytes to store the object in the memory, a file or database, or transmit it through the network. Its main purpose is to save the state of an object in order to be able to recreate it when needed. The reverse process is called deserialization. Hazelcast offers you its own native serialization methods. You will see these methods throughout this chapter.
Hazelcast serializes all your objects before sending them to the server. The boolean, number,string and Long types are serialized natively and you cannot override this behavior. The following table is the conversion of types for the Java server side.
| Node.js | Java |
|---|---|
| boolean | Boolean |
| number | Byte, Short, Integer, Float, Double |
| string | String |
| Long | Long |
Note: A
numbertype is serialized asDoubleby default. You can configure this behavior using theSerializationConfig.defaultNumberTypemethod.
Arrays of the above types can be serialized as boolean[], byte[], short[], int[], float[], double[], long[] and string[] for the Java server side, respectively.
Serialization Priority
When Hazelcast Node.js client serializes an object:
-
It first checks whether the object is null.
-
If the above check fails, then it checks if it is an instance of
IdentifiedDataSerializable. -
If the above check fails, then it checks if it is an instance of
Portable. -
If the above check fails, then it checks if it is an instance of one of the default types (see above default types).
-
If the above check fails, then it looks for a user-specified Custom Serialization.
-
If the above check fails, it will use the registered Global Serialization if one exists.
-
If the above check fails, then the Node.js client uses
JSON Serializationby default.
However, JSON Serialization is not the best way of serialization in terms of performance and interoperability between the clients in different languages. If you want the serialization to work faster or you use the clients in different languages, Hazelcast offers its own native serialization methods, such as IdentifiedDataSerializable Serialization and Portable Serialization.
Or, if you want to use your own serialization method, you can use a Custom Serialization.
NOTE: Hazelcast Node.js client is a TypeScript-based project but JavaScript does not have interfaces. Therefore, some interfaces are given to the user by using the TypeScript files that have
.tsextension. In this guide, implementing an interface means creating an object to have the necessary functions that are listed in the interface inside the.tsfile. Also, this object is mentioned asan instance of the interface. You can search the API Documentation or GitHub repository for a required interface.
For a faster serialization of objects, Hazelcast recommends to implement the IdentifiedDataSerializable interface. The following is an example of an object implementing this interface:
function Address(street, zipCode, city, state) {
this.street = street;
this.zipCode = zipCode;
this.city = city;
this.state = state;
}
Address.prototype.getClassId = function () {
return 1;
};
Address.prototype.getFactoryId = function () {
return 1;
};
Address.prototype.writeData = function (objectDataOutput) {
objectDataOutput.writeUTF(this.street);
objectDataOutput.writeInt(this.zipCode);
objectDataOutput.writeUTF(this.city);
objectDataOutput.writeUTF(this.state);
};
Address.prototype.readData = function (objectDataInput) {
this.street = objectDataInput.readUTF();
this.zipCode = objectDataInput.readInt();
this.city = objectDataInput.readUTF();
this.state = objectDataInput.readUTF();
};The IdentifiedDataSerializable interface uses getClassId() and getFactoryId() to reconstitute the object. To complete the implementation, IdentifiedDataSerializableFactory should also be implemented and registered into SerializationConfig which can be accessed from Config.serializationConfig. The factory's responsibility is to return an instance of the right IdentifiedDataSerializable object, given the classId.
A sample IdentifiedDataSerializableFactory could be implemented as follows:
function MyIdentifiedFactory() {
}
MyIdentifiedFactory.prototype.create = function (type) {
if (type === 1) {
return new Address();
}
};The last step is to register the IdentifiedDataSerializableFactory to the SerializationConfig.
Programmatic Configuration:
var config = new Config.ClientConfig();
config.serializationConfig.dataSerializableFactories[1] = new MyIdentifiedFactory();Declarative Configuration:
{
"serialization": {
"dataSerializableFactories": [
{
"path": "address.js",
"exportedName": "MyIdentifiedFactory",
"factoryId": 1
}
]
}
}Note that the ID that is passed to the SerializationConfig is same as the factoryId that the Address object returns.
As an alternative to the existing serialization methods, Hazelcast offers portable serialization. To use it, you need to implement the Portable interface. Portable serialization has the following advantages:
- Supporting multiversion of the same object type.
- Fetching individual fields without having to rely on the reflection.
- Querying and indexing support without deserialization and/or reflection.
In order to support these features, a serialized Portable object contains meta information like the version and concrete location of the each field in the binary data. This way Hazelcast is able to navigate in the binary data and deserialize only the required field without actually deserializing the whole object which improves the query performance.
With multiversion support, you can have two members where each of them having different versions of the same object, and Hazelcast will store both meta information and use the correct one to serialize and deserialize portable objects depending on the member. This is very helpful when you are doing a rolling upgrade without shutting down the cluster.
Also note that portable serialization is totally language independent and is used as the binary protocol between Hazelcast server and clients.
A sample portable implementation of a Foo class looks like the following:
function Foo(foo) {
this.foo = foo;
}
Foo.prototype.getClassId = function () {
return 1;
};
Foo.prototype.getFactoryId = function () {
return 1;
};
Foo.prototype.writePortable = function (portableWriter) {
portableWriter.writeUTF('foo', this.foo);
};
Foo.prototype.readPortable = function (portableReader) {
this.foo = portableReader.readUTF('foo');
};Similar to IdentifiedDataSerializable, a Portable object must provide classId and factoryId. The factory object will be used to create the Portable object given the classId.
A sample PortableFactory could be implemented as follows:
function MyPortableFactory() {
}
MyPortableFactory.prototype.create = function (type) {
if (type === 1) {
return new Foo();
}
};The last step is to register the PortableFactory to the SerializationConfig.
Programmatic Configuration:
var config = new Config.ClientConfig();
config.serializationConfig.portableFactories[1] = new MyPortableFactory();Declarative Configuration:
{
"serialization": {
"portableFactories": [
{
"path": "foo.js",
"exportedName": "MyPortableFactory",
"factoryId": 1
}
]
}
}Note that the ID that is passed to the SerializationConfig is same as the factoryId that Foo object returns.
Hazelcast lets you plug a custom serializer to be used for serialization of objects.
Let's say you have an object Musician and you would like to customize the serialization. The reason might be that you want to use an external serializer for only one object.
function Musician(name) {
this.name = name;
}
Musician.prototype.hzGetCustomId = function () {
return 10;
};Let's say your custom MusicianSerializer will serialize Musician.
function MusicianSerializer() {
}
MusicianSerializer.prototype.getId = function () {
return 10;
}
MusicianSerializer.prototype.write = function (objectDataOutput, object) {
objectDataOutput.writeInt(object.name.length);
for (var i = 0; i < object.name.length; i++) {
objectDataOutput.writeInt(object.name.charCodeAt(i));
}
}
MusicianSerializer.prototype.read = function (objectDataInput) {
var len = objectDataInput.readInt();
var name = '';
for (var i = 0; i < len; i++) {
name = name + String.fromCharCode(objectDataInput.readInt());
}
return new Musician(name);
}Note that the serializer id must be unique as Hazelcast will use it to lookup the MusicianSerializer while it deserializes the object. Now the last required step is to register the MusicianSerializer to the configuration.
Programmatic Configuration:
var config = new Config.ClientConfig();
config.serializationConfig.customSerializers.push(new MusicianSerializer());Declarative Configuration:
{
"serialization": {
"defaultNumberType": "integer",
"isBigEndian": false,
"serializers": [
{
"path": "Musician.js",
"exportedName": "MusicianSerializer",
"typeId": 10
}
]
}
}From now on, Hazelcast will use MusicianSerializer to serialize Musician objects.
The global serializer is identical to custom serializers from the implementation perspective. The global serializer is registered as a fallback serializer to handle all other objects if a serializer cannot be located for them.
By default, JSON serialization is used if the object is not IdentifiedDataSerializable or Portable or there is no custom serializer for it. When you configure a global serializer, it is used instead of JSON serialization.
You can use the global serialization for the following cases:
- Third party serialization frameworks can be integrated using the global serializer.
- For your custom objects, you can implement a single serializer to handle all of them.
A sample global serializer that integrates with a third party serializer is shown below.
function GlobalSerializer() {
}
GlobalSerializer.prototype.getId = function () {
return 20;
};
GlobalSerializer.prototype.write = function (objectDataOutput, object) {
objectDataOutput.writeByteArray(SomeThirdPartySerializer.serialize(object))
};
GlobalSerializer.prototype.read = function (objectDataInput) {
return SomeThirdPartySerializer.deserialize(objectDataInput.readByteArray());
};You should register the global serializer in the configuration.
Programmatic Configuration:
config.serializationConfig.globalSerializer = new GlobalSerializer();Declarative Configuration:
{
"serialization": {
"defaultNumberType": "integer",
"isBigEndian": false,
"globalSerializer": {
"path": "SomeThirdPartySerializer.js",
"exportedName": "SomeThirdPartySerializer"
},
}
}All network related configuration of Hazelcast Node.js client is performed via the network element in the declarative configuration file, or in the object ClientNetworkConfig when using programmatic configuration. Let's first give the examples for these two approaches. Then we will look at its sub-elements and attributes.
Here is an example of configuring the network for Node.js Client declaratively.
{
"network": {
"clusterMembers": [
"10.1.1.21",
"10.1.1.22:5703"
],
"smartRouting": true,
"redoOperation": true,
"connectionTimeout": 6000,
"connectionAttemptPeriod": 5000,
"connectionAttemptLimit": 5
}
}Here is an example of configuring the network for Node.js Client programmatically.
var clientConfig = new Config.ClientConfig();
clientConfig.networkConfig.addresses.push('10.1.1.21', '10.1.1.22:5703');
clientConfig.networkConfig.smartRouting = true;
clientConfig.networkConfig.redoOperation = true;
clientConfig.networkConfig.connectionTimeout = 6000;
clientConfig.networkConfig.connectionAttemptPeriod = 5000;
clientConfig.networkConfig.connectionAttemptLimit = 5;Address list is the initial list of cluster addresses which the client will connect to. The client uses this list to find an alive member. Although it may be enough to give only one address of a member in the cluster (since all members communicate with each other), it is recommended that you give the addresses for all the members.
Declarative:
{
"network": {
"clusterMembers": [
"10.1.1.21",
"10.1.1.22:5703"
]
}
}Programmatic:
var clientConfig = new Config.ClientConfig();
clientConfig.networkConfig.addresses.push('10.1.1.21', '10.1.1.22:5703');If the port part is omitted, then 5701, 5702 and 5703 will be tried in a random order.
You can specify multiple addresses with or without the port information as seen above. The provided list is shuffled and tried in a random order. Its default value is localhost.
Smart routing defines whether the client mode is smart or unisocket. See Node.js Client Operation Modes section for the description of smart and unisocket modes.
The following are example configurations.
Declarative:
{
"network": {
"smartRouting": true
}
}Programmatic:
var clientConfig = new Config.ClientConfig();
clientConfig.networkConfig.smartRouting = true;Its default value is true (smart client mode).
It enables/disables redo-able operations. While sending the requests to the related members, the operations can fail due to various reasons. Read-only operations are retried by default. If you want to enable retry for the other operations, you can set the redoOperation to true.
Declarative:
{
"network": {
"redoOperation": true
}
}Programmatic:
var clientConfig = new Config.ClientConfig();
clientConfig.networkConfig.redoOperation = true;Its default value is false (disabled).
Connection timeout is the timeout value in milliseconds for the members to accept the client connection requests.
If the member does not respond within the timeout, the client will retry to connect as many as ClientNetworkConfig.connectionAttemptLimit times.
The following are the example configurations.
Declarative:
{
"network": {
"connectionTimeout": 6000
}
}Programmatic:
var clientConfig = new Config.ClientConfig();
clientConfig.networkConfig.connectionTimeout = 6000;Its default value is 5000 milliseconds.
While the client is trying to connect initially to one of the members in the ClientNetworkConfig.addresses, that member might not be available at that moment. Instead of giving up, throwing an error and stopping the client, the client will retry as many as ClientNetworkConfig.connectionAttemptLimit times. This is also the case when the previously established connection between the client and that member goes down.
The following are example configurations.
Declarative:
{
"network": {
"connectionAttemptLimit": 5
}
}Programmatic:
var clientConfig = new Config.ClientConfig();
clientConfig.networkConfig.connectionAttemptLimit = 5;Its default value is 2.
Connection attempt period is the duration in milliseconds between the connection attempts defined by ClientNetworkConfig.connectionAttemptLimit.
The following are example configurations.
Declarative:
{
"network": {
"connectionAttemptPeriod": 5000
}
}Programmatic:
var clientConfig = new Config.ClientConfig();
clientConfig.networkConfig.connectionAttemptPeriod = 5000;Its default value is 3000 milliseconds.
You can use TLS/SSL to secure the connection between the clients and members. If you want to enable TLS/SSL for the client-cluster connection, you should set an SSL configuration. Please see TLS/SSL section.
As explained in the TLS/SSL section, Hazelcast members have key stores used to identify themselves (to other members) and Hazelcast Node.js clients have certificate authorities used to define which members they can trust. Hazelcast has the mutual authentication feature which allows the Node.js clients also to have their private keys and public certificates, and members to have their certificate authorities so that the members can know which clients they can trust. See the Mutual Authentication section.
The purpose of Hazelcast Cloud Discovery is to provide the clients to use IP addresses provided by hazelcast orchestrator. To enable Hazelcast Cloud Discovery, specify a token for the discoveryToken field and set the enabled field to true.
The following are example configurations.
Declarative:
{
"group": {
"name": "hazel",
"password": "cast"
},
"network": {
"hazelcastCloud": {
"discoveryToken": "EXAMPLE_TOKEN",
"enabled": true
}
}
}
Programmatic:
var clientConfig = new Config.ClientConfig();
clientConfig.groupConfig.name = 'hazel';
clientConfig.groupConfig.password = 'cast';
clientConfig.networkConfig.cloudConfig.enabled = true;
clientConfig.networkConfig.cloudConfig.discoveryToken = 'EXAMPLE_TOKEN';To be able to connect to the provided IP addresses, you should use secure TLS/SSL connection between the client and members. Therefore, you should set an SSL configuration as described in the previous section.
This chapter describes the security features of Hazelcast Node.js client. These include using TLS/SSL for connections between members and between clients and members, and mutual authentication. These security features require Hazelcast IMDG Enterprise edition.
One of the offers of Hazelcast is the TLS/SSL protocol which you can use to establish an encrypted communication across your cluster with key stores and trust stores.
- A Java
keyStoreis a file that includes a private key and a public certificate. The equivalent of a key store is the combination ofkeyandcertfiles at the Node.js client side. - A Java
trustStoreis a file that includes a list of certificates trusted by your application which is named as "certificate authority". The equivalent of a trust store is acafile at the Node.js client side.
You should set keyStore and trustStore before starting the members. See the next section on setting keyStore and trustStore on the server side.
Hazelcast allows you to encrypt socket level communication between Hazelcast members and between Hazelcast clients and members, for end to end encryption. To use it, see the TLS/SSL for Hazelcast Members section.
Hazelcast Node.js clients which support TLS/SSL should have the following user supplied SSL options object, to pass to
tls.connect of Node.js:
var fs = require('fs');
var clientConfig = new Config.ClientConfig();
clientConfig.networkConfig.sslOptions = {
rejectUnauthorized: true,
ca: [fs.readFileSync(__dirname + '/server-cert.pem')],
servername: 'foo.bar.com'
};As explained above, Hazelcast members have key stores used to identify themselves (to other members) and Hazelcast clients have trust stores used to define which members they can trust.
Using mutual authentication, the clients also have their key stores and members have their trust stores so that the members can know which clients they can trust.
To enable mutual authentication, firstly, you need to set the following property at the server side in the hazelcast.xml file:
<network>
<ssl enabled="true">
<properties>
<property name="javax.net.ssl.mutualAuthentication">REQUIRED</property>
</properties>
</ssl>
</network>You can see the details of setting mutual authentication on the server side in the Mutual Authentication section of the Hazelcast IMDG Reference Manual.
At the Node.js client side, you need to supply an SSL options object to pass to
tls.connect of Node.js.
There are two ways to provide this object to the client:
- Using the built-in
BasicSSLOptionsFactorybundled with the client. - Writing an
SSLOptionsFactory.
Below subsections describe each way.
Using the Built-in BasicSSLOptionsFactory
Hazelcast Node.js client includes a utility factory class that creates the necessary options object out of the supplied
properties. All you need to do is to specify your factory as BasicSSLOptionsFactory and provide the following options:
caPathkeyPathcertPathservernamerejectUnauthorizedciphers
See tls.connect of Node.js for the descriptions of each option.
caPath,keyPathandcertPathdefine the file path to the respective file that stores such information.
{
"network": {
"ssl": {
"enabled": true,
"factory": {
"exportedName": "BasicSSLOptionsFactory",
"properties": {
"caPath": "ca.pem",
"keyPath": "key.pem",
"certPath": "cert.pem",
"rejectUnauthorized": false
}
}
}
}
}If these options are not enough for your application, you may write your own options factory and instruct the client to get the options from it, as explained below.
Writing an SSLOptionsFactory
In order to use the full range of options provided to tls.connect of Node.js, you may write your own factory object.
An example configuration is shown below.
{
"network": {
"ssl": {
"enabled": true,
"factory": {
"path": "my_factory.js",
"exportedName": "SSLFactory",
"properties": {
"caPath": "ca.pem",
"keyPath": "key.pem",
"certPath": "cert.pem",
"keepOrder": true
}
}
}
}
}An example of a factory, My_Factory.js, is shown below.
function SSLFactory() {
}
SSLFactory.prototype.init = function(props) {
this.caPath = props.caPath;
this.keyPath = props.keyPath;
this.certPath = props.certPath;
this.keepOrder = props.userDefinedProperty1;
};
SSLFactory.prototype.getSSLOptions = function() {
var sslOpts = {
servername: 'foo.bar.com',
rejectUnauthorized: true,
ca: fs.readFileSync(this.caPath)
key: fs.readFileSync(this.keyPath),
cert: fs.readFileSync(this.certPath),
};
if (this.keepOrder) {
sslOpts.honorCipherOrder = true;
}
return sslOpts;
};
exports.SSLFactory = SSLFactory;The client loads MyFactory.js at runtime and creates an instance of SSLFactory. It then calls the method init with
the properties section in the JSON configuration file. Lastly, the client calls the method getSSLOptions of SSLFactory to create the options object.
For information about the path resolution, see the Loading Objects and Path Resolution section.
This chapter provides information on how you can use Hazelcast IMDG's data structures in the Node.js client, after giving some basic information including an overview to the client API, operation modes of the client and how it handles the failures.
Most of the functions in the API return Promise. Therefore, you need to be familiar with the concept of promises to use the Node.js client. If not, you can learn about them using various online resources, e.g., the Promise JS website.
Promises provide a better way of working with callbacks. You can chain asynchronous functions by the then() function of promise. Also, you can use async/await, if you use Node.js 8 and higher versions.
If you are ready to go, let's start to use Hazelcast Node.js client.
The first step is the configuration. You can configure the Node.js client declaratively or programmatically. We will use the programmatic approach throughout this chapter. See the Programmatic Configuration section for details.
The following is an example on how to create a ClientConfig object and configure it programmatically:
var clientConfig = new Config.ClientConfig();
clientConfig.groupConfig.name = 'dev';
clientConfig.networkConfig.addresses.push('10.90.0.1', '10.90.0.2:5702');The second step is initializing the HazelcastClient to be connected to the cluster:
Client.newHazelcastClient(clientConfig).then(function (client) {
// some operation
});This client object is your gateway to access all the Hazelcast distributed objects.
Let's create a map and populate it with some data, as shown below.
var client;
var mapCustomers;
Client.newHazelcastClient(clientConfig).then(function (res) {
client = res;
return client.getMap('customers');
}).then(function (mp) {
mapCustomers = mp;
return mapCustomers.put('1', new Customer('Furkan', 'Senharputlu'));
}).then(function () {
return mapCustomers.put('2', new Customer("Joe", "Smith"));
}).then(function () {
return mapCustomers.put('3', new Customer("Muhammet", "Ali"));
});As the final step, if you are done with your client, you can shut it down as shown below. This will release all the used resources and close connections to the cluster.
...
.then(function () {
client.shutdown();
});The client has two operation modes because of the distributed nature of the data and cluster: smart and unisocket.
In the smart mode, the clients connect to each cluster member. Since each data partition uses the well known and consistent hashing algorithm, each client can send an operation to the relevant cluster member, which increases the overall throughput and efficiency. Smart mode is the default mode.
For some cases, the clients can be required to connect to a single member instead of each member in the cluster. Firewalls, security or some custom networking issues can be the reason for these cases.
In the unisocket client mode, the client will only connect to one of the configured addresses. This single member will behave as a gateway to the other members. For any operation requested from the client, it will redirect the request to the relevant member and return the response back to the client returned from this member.
There are two main failure cases you should be aware of. Below sections explain these and the configurations you can perform to achieve proper behavior.
While the client is trying to connect initially to one of the members in the ClientNetworkConfig.addressList, all the members might not be available. Instead of giving up, throwing an error and stopping the client, the client will retry as many as connectionAttemptLimit times.
You can configure connectionAttemptLimit for the number of times you want the client to retry connecting. See the Setting Connection Attempt Limit section.
The client executes each operation through the already established connection to the cluster. If this connection(s) disconnects or drops, the client will try to reconnect as configured.
While sending the requests to the related members, the operations can fail due to various reasons. Read-only operations are retried by default. If you want to enable retrying for the other operations, you can set the redoOperation to true. See the Enabling Redo Operation section.
You can set a timeout for retrying the operations sent to a member. This can be provided by using the property hazelcast.client.invocation.timeout.seconds in ClientConfig.properties. The client will retry an operation within this given period, of course, if it is a read-only operation or you enabled the redoOperation as stated in the above paragraph. This timeout value is important when there is a failure resulted by either of the following causes:
- Member throws an exception.
- Connection between the client and member is closed.
- Client’s heartbeat requests are timed out.
When a connection problem occurs, an operation is retried if it is certain that it has not run on the member yet or if it is idempotent such as a read-only operation, i.e., retrying does not have a side effect. If it is not certain whether the operation has run on the member, then the non-idempotent operations are not retried. However, as explained in the first paragraph of this section, you can force all the client operations to be retried (redoOperation) when there is a connection failure between the client and member. But in this case, you should know that some operations may run multiple times causing conflicts. For example, assume that your client sent a queue.offer operation to the member and then the connection is lost. Since there will be no response for this operation, you will not know whether it has run on the member or not. If you enabled redoOperation, it means this operation may run again, which may cause two instances of the same object in the queue.
Most of the distributed data structures are supported by the Node.js client. In this chapter, you will learn how to use these distributed data structures.
Hazelcast Map (IMap) is a distributed map. Through the Node.js client, you can perform operations like reading and writing from/to a Hazelcast Map with the well known get and put methods. For details, see the Map section in the Hazelcast IMDG Reference Manual.
A Map usage example is shown below.
var map;
client.getMap('myMap').then(function (mp) {
map = mp;
return map.put(1, 'Furkan');
}).then(function (oldValue) {
return map.get(1);
}).then(function (value) {
console.log(value); // Furkan
return map.remove(1);
});Hazelcast MultiMap is a distributed and specialized map where you can store multiple values under a single key. For details, see the MultiMap section in the Hazelcast IMDG Reference Manual.
A MultiMap usage example is shown below.
var multiMap;
client.getMultiMap('myMultiMap').then(function (mmp) {
multiMap = mmp;
return multiMap.put(1, 'Furkan')
}).then(function () {
return multiMap.put(1, 'Mustafa');
}).then(function () {
return multiMap.get(1);
}).then(function (values) {
console.log(values.get(0), values.get(1)); // Furkan Mustafa
});Hazelcast ReplicatedMap is a distributed key-value data structure where the data is replicated to all members in the cluster. It provides full replication of entries to all members for high speed access. For details, see the Replicated Map section in the Hazelcast IMDG Reference Manual.
A Replicated Map usage example is shown below.
var replicatedMap;
client.getReplicatedMap('myReplicatedMap').then(function (rmp) {
replicatedMap = rmp;
return replicatedMap.put(1, 'Furkan')
}).then(function () {
return replicatedMap.put(2, 'Ahmet');
}).then(function () {
return replicatedMap.get(2);
}).then(function (value) {
console.log(value); // Ahmet
});Hazelcast Queue (IQueue) is a distributed queue which enables all cluster members to interact with it. For details, see the Queue section in the Hazelcast IMDG Reference Manual.
A Queue usage example is shown below.
var queue;
client.getQueue('myQueue').then(function (q) {
queue = q;
return queue.offer('Furkan');
}).then(function () {
return queue.peek();
}).then(function (head) {
console.log(head); // Furkan
});Hazelcast Set (ISet) is a distributed set which does not allow duplicate elements. For details, see the Set section in the Hazelcast IMDG Reference Manual.
A Set usage example is shown below.
var set;
hazelcastClient.getSet('mySet').then(function (s) {
set = s;
return set.add('Furkan');
}).then(function () {
return set.contains('Furkan');
}).then(function (val) {
console.log(val); // true
});Hazelcast List (IList) is a distributed list which allows duplicate elements and preserves the order of elements. For details, see the List section in the Hazelcast IMDG Reference Manual.
A List usage example is shown below.
var list;
hazelcastClient.getList('myList').then(function (l) {
list = l;
return list.add('Muhammet Ali');
}).then(function () {
return list.add('Ahmet');
}).then(function () {
return list.add('Furkan');
}).then(function () {
return list.size();
}).then(function (size) {
console.log(size); // 3
});Hazelcast Ringbuffer is a replicated but not partitioned data structure that stores its data in a ring-like structure. You can think of it as a circular array with a given capacity. Each Ringbuffer has a tail and a head. The tail is where the items are added and the head is where the items are overwritten or expired. You can reach each element in a Ringbuffer using a sequence ID, which is mapped to the elements between the head and tail (inclusive) of the Ringbuffer. For details, see the Ringbuffer section in the Hazelcast IMDG Reference Manual.
A Ringbuffer usage example is shown below.
var ringbuffer;
hazelcastClient.getRingbuffer('myRingbuffer').then(function (buffer) {
ringbuffer = buffer;
return ringbuffer.addAll(['Muhammet Ali', 'Ahmet', 'Furkan']);
}).then(function () {
return Promise.all([
ringbuffer.readOne(0), ringbuffer.readOne(1), ringbuffer.readOne(2)
]);
}).then(function (brothers) {
console.log(brothers); // [ 'Muhammet Ali', 'Ahmet', 'Furkan' ]
});Hazelcast ReliableTopic is a distributed topic implementation backed up by the Ringbuffer data structure. For details, see the Reliable Topic section in the Hazelcast IMDG Reference Manual.
A Reliable Topic usage example is shown below.
var topic;
hazelcastClient.getReliableTopic('myReliableTopic').then(function (t) {
topic = t;
topic.addMessageListener(function (message) {
console.log(message.messageObject);
});
return topic.publish('Hello to distributed world!');
});Hazelcast Lock (ILock) is a distributed lock implementation. You can synchronize Hazelcast members and clients using a Lock. For details, see the Lock section in the Hazelcast IMDG Reference Manual.
A Lock usage example is shown below.
var lock;
hazelcastClient.getLock('myLock').then(function (l) {
lock = l;
return lock.lock();
}).then(function () {
// cluster wide critical section
}).finally(function () {
return lock.unlock();
});Hazelcast Atomic Long (IAtomicLong) is the distributed long which offers most of the operations such as get, set, getAndSet, compareAndSet and incrementAndGet. For details, see the Atomic Long section in the Hazelcast IMDG Reference Manual.
An Atomic Long usage example is shown below.
var atomicLong;
hazelcastClient.getAtomicLong('myAtomicLong').then(function (counter) {
atomicLong = counter;
return atomicLong.addAndGet(3);
}).then(function (value) {
return atomicLong.get();
}).then(function (value) {
console.log('counter: ' + value); // counter: 3
});Hazelcast Semaphore (ISemaphore) is a distributed semaphore implementation. For details, see the Semaphore section in the Hazelcast IMDG Reference Manual.
A Semaphore usage example is shown below.
var semaphore;
hazelcastClient.getSemaphore('mySemaphore').then(function (s) {
semaphore = s;
return semaphore.init(10);
}).then(function () {
return semaphore.acquire(5);
}).then(function () {
return semaphore.availablePermits();
}).then(function (res) {
console.log(res); // 5
});Hazelcast PNCounter (Positive-Negative Counter) is a CRDT positive-negative counter implementation. It is an eventually consistent counter given there is no member failure. For details, see the PN Counter section in the Hazelcast IMDG Reference Manual.
A PN Counter usage example is shown below.
var pnCounter;
hazelcastClient.getPNCounter('myPNCounter').then(function (counter) {
pnCounter = counter;
return pnCounter.addAndGet(5);
}).then(function (value) {
console.log(value); // 5
return pnCounter.decrementAndGet();
}).then(function (value) {
console.log(value); // 4
});Hazelcast FlakeIdGenerator is used to generate cluster-wide unique identifiers. Generated identifiers are long primitive values and are k-ordered (roughly ordered). IDs are in the range from 0 to 2^63-1 (maximum signed long value). For details, see the FlakeIdGenerator section in the Hazelcast IMDG Reference Manual.
A Flake ID Generator usage example is shown below.
var flakeIdGenerator;
hazelcastClient.getFlakeIdGenerator('myFlakeIdGenerator').then(function (gen) {
flakeIdGenerator = gen;
return flakeIdGenerator.newId();
}).then(function (value) {
console.log('New id: ' + value.toString());
});This chapter explains when various events are fired and describes how you can add event listeners on a Hazelcast Node.js client. These events can be categorized as cluster and distributed data structure events.
You can add event listeners to a Hazelcast Node.js client. You can configure the following listeners to listen to the events on the client side:
- Membership Listener: Notifies when a member joins to/leaves the cluster, or when an attribute is changed in a member.
- Distributed Object Listener: Notifies when a distributed object is created or destroyed throughout the cluster.
- Lifecycle Listener: Notifies when the client is starting, started, shutting down and shutdown.
You can add the following types of member events to the ClusterService.
memberAdded: A new member is added to the cluster.memberRemoved: An existing member leaves the cluster.memberAttributeChanged: An attribute of a member is changed. See the Defining Member Attributes section in the Hazelcast IMDG Reference Manual to learn about member attributes.
The ClusterService object exposes an ClusterService.on() function that allows one or more functions to be attached to the member events emitted by the object.
The following is a membership listener registration by using the ClusterService.on() function.
client.clusterService.on('memberAdded', function (member) {
console.log('Member Added: The address is', member.address.toString());
});The memberAttributeChanged has its own type of event named as MemberAttributeEvent. When there is an attribute change on the member, this event is fired.
See the following example.
client.clusterService.on('memberAttributeChanged', function (memberAttributeEvent) {
console.log('Member Attribute Changed: The address is', memberAttributeEvent.member.address.toString());
});The events for distributed objects are invoked when they are created and destroyed in the cluster. After the events, a listener callback function is called. The type of the callback function should be DistributedObjectListener. The parameter of the function is DistributedObjectEvent including following fields:
serviceName: Service name of the distributed object.objectName: Name of the distributed object.eventType: Type of the invoked event. It can becreatedordestroyed.
The following is an example of adding a DistributedObjectListener.
client.addDistributedObjectListener(function (distributedObjectEvent) {
console.log('Distributed object event >>> ',
distributedObjectEvent.serviceName,
distributedObjectEvent.objectName,
distributedObjectEvent.eventType
);
}).then(function () {
var mapname = 'test';
//this causes a created event
client.getMap(mapname);
//this causes no event because map was already created
client.getMap(mapname);
});The LifecycleListener interface notifies for the following events:
starting: A client is starting.started: A client has started.shuttingDown: A client is shutting down.shutdown: A client’s shutdown has completed.
The following is an example of the LifecycleListener that is added to the ClientConfig object and its output.
var clientConfig = new Config.ClientConfig();
clientConfig.listeners.addLifecycleListener(function (state) {
console.log('Lifecycle Event >>> ' + state);
});
Client.newHazelcastClient(clientConfig).then(function (hazelcastClient) {
hazelcastClient.shutdown();
});Output:
Lifecycle Event >>> starting
[DefaultLogger] INFO at ConnectionAuthenticator: Connection to 10.216.1.62:5701 authenticated
[DefaultLogger] INFO at ClusterService: Members received.
[ Member {
address: Address { host: '10.216.1.62', port: 5701, type: 4 },
uuid: 'dc001432-7868-4ced-9161-5649ff6f31fc',
isLiteMember: false,
attributes: {} } ]
Lifecycle Event >>> started
[DefaultLogger] INFO at HazelcastClient: Client started
Lifecycle Event >>> shuttingDown
Lifecycle Event >>> shutdown
Process finished with exit code 0
You can add event listeners to the distributed data structures.
NOTE: Hazelcast Node.js client is a TypeScript-based project but JavaScript does not have interfaces. Therefore, some interfaces are given to the user by using the TypeScript files that have
.tsextension. In this guide, implementing an interface means creating an object to have the necessary functions that are listed in the interface inside the.tsfile. Also, this object is mentioned asan instance of the interface. You can search the API Documentation or GitHub repository for a required interface.
You can listen to map-wide or entry-based events by using the functions in the MapListener interface. Every function type in this interface is one of the EntryEventListener and MapEventListener types. To listen to these events, you need to implement the relevant EntryEventListener and MapEventListener functions in the MapListener interface.
An entry-based event is fired after the operations that affect a specific entry. For example, IMap.put(), IMap.remove() or IMap.evict(). You should use the EntryEventListener type to listen to these events. An EntryEvent object is passed to the listener function.
See the following example.
var entryEventListener = {
added: function (entryEvent) {
console.log('Entry Added:', entryEvent.key, entryEvent.value); // Entry Added: 1 Furkan
}
};
map.addEntryListener(entryEventListener, undefined, true).then(function () {
return map.put('1', 'Furkan');
});A map-wide event is fired as a result of a map-wide operation. For example, IMap.clear() or IMap.evictAll(). You should use the MapEventListener type to listen to these events. A MapEvent object is passed to the listener function.
See the following example.
var mapEventListener = {
mapCleared: function (mapEvent) {
console.log('Map Cleared:', mapEvent.numberOfAffectedEntries); // Map Cleared: 3
}
};
map.addEntryListener(mapEventListener).then(function () {
return map.put('1', 'Muhammet Ali');
}).then(function () {
return map.put('2', 'Ahmet');
}).then(function () {
return map.put('3', 'Furkan');
}).then(function () {
return map.clear();
});This chapter explains how you can use Hazelcast IMDG's entry processor implementation in the Node.js client.
Hazelcast supports entry processing. An entry processor is a function that executes your code on a map entry in an atomic way.
An entry processor is a good option if you perform bulk processing on an IMap. Usually you perform a loop of keys -- executing IMap.get(key), mutating the value and finally putting the entry back in the map using IMap.put(key,value). If you perform this process from a client or from a member where the keys do not exist, you effectively perform two network hops for each update: the first to retrieve the data and the second to update the mutated value.
If you are doing the process described above, you should consider using entry processors. An entry processor executes a read and updates upon the member where the data resides. This eliminates the costly network hops described above.
NOTE: Entry processor is meant to process a single entry per call. Processing multiple entries and data structures in an entry processor is not supported as it may result in deadlocks on the server side.
Hazelcast sends the entry processor to each cluster member and these members apply it to the map entries. Therefore, if you add more members, your processing completes faster.
The IMap interface provides the following functions for entry processing:
executeOnKeyprocesses an entry mapped by a key.executeOnKeysprocesses entries mapped by a list of keys.executeOnEntriescan process all entries in a map with a defined predicate. Predicate is optional.
In the Node.js client, an EntryProcessor should be IdentifiedDataSerializable or Portable because the server should be able to deserialize it to process.
The following is an example for EntryProcessor which is IdentifiedDataSerializable.
function IdentifiedEntryProcessor(value) {
this.value = value;
}
IdentifiedEntryProcessor.prototype.readData = function (inp) {
this.value = inp.readUTF();
};
IdentifiedEntryProcessor.prototype.writeData = function (outp) {
outp.writeUTF(this.value);
};
IdentifiedEntryProcessor.prototype.getFactoryId = function () {
return 5;
};
IdentifiedEntryProcessor.prototype.getClassId = function () {
return 1;
};Now, you need to make sure that the Hazelcast member recognizes the entry processor. For this, you need to implement the Java equivalent of your entry processor and its factory, and create your own compiled class or JAR files. For adding your own compiled class or JAR files to the server's CLASSPATH, see the Adding User Library to CLASSPATH section.
The following is the Java equivalent of the entry processor in Node.js client given above:
import com.hazelcast.map.AbstractEntryProcessor;
import com.hazelcast.nio.ObjectDataInput;
import com.hazelcast.nio.ObjectDataOutput;
import com.hazelcast.nio.serialization.IdentifiedDataSerializable;
import java.io.IOException;
import java.util.Map;
public class IdentifiedEntryProcessor extends AbstractEntryProcessor<String, String> implements IdentifiedDataSerializable {
static final int CLASS_ID = 1;
private String value;
public IdentifiedEntryProcessor() {
}
@Override
public int getFactoryId() {
return IdentifiedFactory.FACTORY_ID;
}
@Override
public int getId() {
return CLASS_ID;
}
@Override
public void writeData(ObjectDataOutput out) throws IOException {
out.writeUTF(value);
}
@Override
public void readData(ObjectDataInput in) throws IOException {
value = in.readUTF();
}
@Override
public Object process(Map.Entry<String, String> entry) {
entry.setValue(value);
return value;
}
}You can implement the above processor’s factory as follows:
import com.hazelcast.nio.serialization.DataSerializableFactory;
import com.hazelcast.nio.serialization.IdentifiedDataSerializable;
public class IdentifiedFactory implements DataSerializableFactory {
public static final int FACTORY_ID = 5;
@Override
public IdentifiedDataSerializable create(int typeId) {
if (typeId == IdentifiedEntryProcessor.CLASS_ID) {
return new IdentifiedEntryProcessor();
}
return null;
}
}Now you need to configure the hazelcast.xml to add your factory as shown below.
<hazelcast>
<serialization>
<data-serializable-factories>
<data-serializable-factory factory-id="5">
IdentifiedFactory
</data-serializable-factory>
</data-serializable-factories>
</serialization>
</hazelcast>The code that runs on the entries is implemented in Java on the server side. The client side entry processor is used to specify which entry processor should be called. For more details about the Java implementation of the entry processor, see the Entry Processor section in the Hazelcast IMDG Reference Manual.
After the above implementations and configuration are done and you start the server where your library is added to its CLASSPATH, you can use the entry processor in the IMap functions. See the following example.
var map;
hazelcastClient.getMap('my-distributed-map').then(function (mp) {
map = mp;
return map.put('key', 'not-processed');
}).then(function () {
return map.executeOnKey('key', new IdentifiedEntryProcessor('processed'));
}).then(function () {
return map.get('key');
}).then(function (value) {
console.log(value); // processed
});Hazelcast partitions your data and spreads it across cluster of members. You can iterate over the map entries and look for certain entries (specified by predicates) you are interested in. However, this is not very efficient because you will have to bring the entire entry set and iterate locally. Instead, Hazelcast allows you to run distributed queries on your distributed map.
- The requested predicate is sent to each member in the cluster.
- Each member looks at its own local entries and filters them according to the predicate. At this stage, key-value pairs of the entries are deserialized and then passed to the predicate.
- The predicate requester merges all the results coming from each member into a single set.
Distributed query is highly scalable. If you add new members to the cluster, the partition count for each member is reduced and thus the time spent by each member on iterating its entries is reduced. In addition, the pool of partition threads evaluates the entries concurrently in each member, and the network traffic is also reduced since only filtered data is sent to the requester.
Predicates Object Operators
The Predicates object offered by the Node.js client includes many operators for your query requirements. Some of them are described below.
equal: Checks if the result of an expression is equal to a given value.notEqual: Checks if the result of an expression is not equal to a given value.instanceOf: Checks if the result of an expression has a certain type.like: Checks if the result of an expression matches some string pattern.%(percentage sign) is the placeholder for many characters,_(underscore) is the placeholder for only one character.greaterThan: Checks if the result of an expression is greater than a certain value.greaterEqual: Checks if the result of an expression is greater than or equal to a certain value.lessThan: Checks if the result of an expression is less than a certain value.lessEqual: Checks if the result of an expression is less than or equal to a certain value.between: Checks if the result of an expression is between two values, inclusively.inPredicate: Checks if the result of an expression is an element of a certain list.not: Checks if the result of an expression is false.regex: Checks if the result of an expression matches some regular expression.
Hazelcast offers the following ways for distributed query purposes:
- Combining Predicates with AND, OR, NOT
- Distributed SQL Query
Assume that you have an employee map containing the values of Employee objects, as coded below.
function Employee(name, age, active, salary) {
this.name = name;
this.age = age;
this.active = active;
this.salary = salary;
}
Employee.prototype.getClassId = function () {
return 1;
}
Employee.prototype.getFactoryId = function () {
return 1;
}
Employee.prototype.readData = function (objectDataInput) {
this.name = objectDataInput.readUTF();
this.age = objectDataInput.readInt();
this.active = objectDataInput.readBoolean();
this.salary = objectDataInput.readDouble();
}
Employee.prototype.writeData = function (objectDataOutput) {
objectDataOutput.writeUTF(this.name);
objectDataOutput.writeInt(this.age);
objectDataOutput.writeBoolean(this.active);
objectDataOutput.writeDouble(this.salary);
}Note that Employee is an IdentifiedDataSerializable object. If you just want to save the Employee objects as byte arrays on the map, you don't need to implement its equivalent on the server-side. However, if you want to query on the employee map, the server needs the Employee objects rather than byte array formats. Therefore, you need to implement its Java equivalent and its data serializable factory on the server side for server to reconstitute the objects from binary formats. After implementing the Java class and its factory, you need to add the factory to the data serializable factories or the portable factories by giving a factory id. The following is an example declarative configuration on the server.
<hazelcast>
...
<serialization>
<data-serializable-factories>
<data-serializable-factory factory-id="1">
mypackage.MyIdentifiedFactory
</data-serializable-factory>
</data-serializable-factories>
</serialization>
...
</hazelcast>Note that before starting the server, you need to compile the Employee and MyIdentifiedFactory classes with server's CLASSPATH and add them to the user-lib directory in the extracted hazelcast-<version>.zip (or tar). See the Adding User Library to CLASSPATH section.
NOTE: You can also make this object
Portableand implement its Java equivalent and portable factory on the server side. Note that querying withPortableobject is faster as compared toIdentifiedDataSerializable.
You can combine predicates by using the and, or and not operators, as shown in the below example.
var map;
client.getMap('employee').then(function (mp) {
map = mp;
var predicate = Predicates.and(Predicates.equal('active', true), Predicates.lessThan('age', 30));
return map.valuesWithPredicate(predicate);
}).then(function (employees) {
// some operations
});In the above example code, predicate verifies whether the entry is active and its age value is less than 30. This predicate is applied to the employee map using the map.valuesWithPredicate(predicate) method. This method sends the predicate to all cluster members and merges the results coming from them.
NOTE: Predicates can also be applied to
keySetandentrySetof the Hazelcast IMDG's distributed map.
SqlPredicate takes the regular SQL where clause. See the following example:
var map;
client.getMap('employee').then(function (mp) {
map = mp;
return map.valuesWithPredicate(new SqlPredicate('active AND age < 30'));
}).then(function (employees) {
// some operations
});AND/OR: <expression> AND <expression> AND <expression>…
active AND age > 30active = false OR age = 45 OR name = 'Joe'active AND ( age > 20 OR salary < 60000 )
Equality: =, !=, <, ⇐, >, >=
<expression> = valueage <= 30name = 'Joe'salary != 50000
BETWEEN: <attribute> [NOT] BETWEEN <value1> AND <value2>
age BETWEEN 20 AND 33 ( same as age >= 20 AND age ⇐ 33 )age NOT BETWEEN 30 AND 40 ( same as age < 30 OR age > 40 )
IN: <attribute> [NOT] IN (val1, val2,…)
age IN ( 20, 30, 40 )age NOT IN ( 60, 70 )active AND ( salary >= 50000 OR ( age NOT BETWEEN 20 AND 30 ) )age IN ( 20, 30, 40 ) AND salary BETWEEN ( 50000, 80000 )
LIKE: <attribute> [NOT] LIKE 'expression'
The % (percentage sign) is the placeholder for multiple characters, an _ (underscore) is the placeholder for only one character.
name LIKE 'Jo%'(true for 'Joe', 'Josh', 'Joseph' etc.)name LIKE 'Jo_'(true for 'Joe'; false for 'Josh')name NOT LIKE 'Jo_'(true for 'Josh'; false for 'Joe')name LIKE 'J_s%'(true for 'Josh', 'Joseph'; false 'John', 'Joe')
ILIKE: <attribute> [NOT] ILIKE 'expression'
ILIKE is similar to the LIKE predicate but in a case-insensitive manner.
name ILIKE 'Jo%'(true for 'Joe', 'joe', 'jOe','Josh','joSH', etc.)name ILIKE 'Jo_'(true for 'Joe' or 'jOE'; false for 'Josh')
REGEX: <attribute> [NOT] REGEX 'expression'
name REGEX 'abc-.*'(true for 'abc-123'; false for 'abx-123')
You can use the __key attribute to perform a predicated search for the entry keys. See the following example:
var personMap;
client.getMap('persons').then(function (mp) {
personMap = mp;
return personMap.put('Ahmet', 28);
}).then(function () {
return personMap.put('Ali', 30);
}).then(function () {
return personMap.put('Furkan', 23);
}).then(function () {
var predicate = new Predicates.sql('__key like F%');
return personMap.valuesWithPredicate(predicate);
}).then(function (startingWithA) {
console.log(startingWithA.get(0)); // 23
});In this example, the code creates a list with the values whose keys start with the letter "F”.
You can use the this attribute to perform a predicated search for entry values. See the following example:
var personMap;
client.getMap('persons').then(function (mp) {
personMap = mp;
return personMap.put('Ahmet', 28);
}).then(function () {
return personMap.put('Ali', 30);
}).then(function () {
return personMap.put('Furkan', 23);
}).then(function () {
var predicate = new Predicates.greaterEqual('this', 27);
return personMap.valuesWithPredicate(predicate);
}).then(function (olderThan27) {
console.log(olderThan27.get(0), olderThan27.get(1)); // 28 30
});In this example, the code creates a list with the values greater than or equal to "27".
The Node.js client provides paging for defined predicates. With its PagingPredicate object, you can get a list of keys, values or entries page by page by filtering them with predicates and giving the size of the pages. Also, you can sort the entries by specifying comparators.
var map;
hazelcastClient.getMap('students').then(function (mp) {
map = mp;
var greaterEqual = Predicates.greaterEqual('age', 18);
var pagingPredicate = Predicates.paging(greaterEqual, 5);
// Set page to retrieve third page
pagingPredicate.setPage(3);
// Retrieve third page
return map.valuesWithPredicate(pagingPredicate)
}).then(function (values) {
// some operations
...
// Set up next page
pagingPredicate.nextPage();
// Retrieve next page
return map.valuesWithPredicate(pagingPredicate);
}).then(function (values) {
// some operations
});If you want to sort the result before paging, you need to specify a comparator object that implements the Comparator interface. Also, this comparator object should be one of IdentifiedDataSerializable or Portable. After implementing this object in Node.js, you need to implement the Java equivalent of it and its factory. The Java equivalent of the comparator should implement java.util.Comparator. Note that the compare function of Comparator on the Java side is the equivalent of the sort function of Comparator on the Node.js side. When you implement the Comparator and its factory, you can add them to the CLASSPATH of the server side. See the Adding User Library to CLASSPATH section.
Also, you can access a specific page more easily with the help of the setPage function. This way, if you make a query for the 100th page, for example, it will get all 100 pages at once instead of reaching the 100th page one by one using the nextPage function.
Fast-Aggregations feature provides some aggregate functions, such as sum, average, max, and min, on top of Hazelcast IMap entries. Their performance is perfect since they run in parallel for each partition and are highly optimized for speed and low memory consumption.
The Aggregators object provides a wide variety of built-in aggregators. The full list is presented below:
countdoubleAvgdoubleSumnumberAvgfixedPointSumfloatingPointSummaxminintegerAvgintegerSumlongAvglongSum
You can use these aggregators with the IMap.aggregate() and IMap.aggregateWithPredicate() functions.
See the following example.
var map;
hazelcastClient.getMap('brothersMap').then(function (mp) {
map = mp;
return map.putAll([
['Muhammet Ali', 30],
['Ahmet', 27],
['Furkan', 23],
]);
}).then(function () {
return map.aggregate(Aggregators.count());
}).then(function (count) {
console.log('There are ' + count + ' brothers.'); // There are 3 brothers.
return map.aggregateWithPredicate(Aggregators.count(), Predicates.greaterThan('this', 25));
}).then(function (count) {
console.log('There are ' + count + ' brothers older than 25.'); // There are 2 brothers older than 25.
return map.aggregate(Aggregators.numberAvg());
}).then(function (avgAge) {
console.log('Average age is ' + avgAge); // Average age is 26.666666666666668
});You can enable the client statistics before starting your clients. There are two properties related to client statistics:
-
hazelcast.client.statistics.enabled: If set totrue, it enables collecting the client statistics and sending them to the cluster. When it istrueyou can monitor the clients that are connected to your Hazelcast cluster, using Hazelcast Management Center. Its default value isfalse. -
hazelcast.client.statistics.period.seconds: Period in seconds the client statistics are collected and sent to the cluster. Its default value is3.
You can enable client statistics and set a non-default period in seconds as follows:
Declarative:
{
"properties": {
"hazelcast.client.statistics.enabled": true,
"hazelcast.client.statistics.period.seconds": 4,
}
}Programmatic:
var config = new Config.ClientConfig();
config.properties['hazelcast.client.statistics.enabled'] = true;
config.properties['hazelcast.client.statistics.period.seconds'] = 4;After enabling the client statistics, you can monitor your clients using Hazelcast Management Center. Please refer to the Monitoring Clients section in the Hazelcast Management Center Reference Manual for more information on the client statistics.
Hazelcast Node.js client has a flexible logging configuration. You can add your custom loggers by providing adapters.
To configure a logger, you need to implement the ILogger interface in your adapter and add it to ClientConfig.properties['hazelcast.logging']. If you set this property to 'off', it does not log anything.
See the following built-in winston logging library example.
var winstonAdapter = {
logger: new (winston.Logger)({
transports: [
new (winston.transports.Console)()
]
}),
levels: [
'error',
'warn',
'info',
'debug',
'silly'
],
log: function (level, className, message, furtherInfo) {
this.logger.log(this.levels[level], className + ' ' + message);
}
};
config.properties['hazelcast.logging'] = winstonAdapter;Hazelcast Node.js client is developed using TypeScript. If you want to help with bug fixes, develop new features or tweak the implementation to your application's needs, you can follow the steps in this section.
Follow the below steps to build and install Hazelcast Node.js client from its source:
- Clone the GitHub repository (https://github.com/hazelcast/hazelcast-nodejs-client.git).
- Run
npm installto automatically download and install all the required modules undernode_modulesdirectory. - Run
npm run compileto compile TypeScript files to JavaScript.
At this point you have all the runnable code (.js) and type declarations (.d.ts) in the lib directory. You may create a link to this module so that your local
applications can depend on your local copy of Hazelcast Node.js client. In order to create a link, run the below command:
npm link
This will create a global link to this module in your computer. Whenever you need to depend on this module from another local project, run the below command:
npm link hazelcast-client
If you are planning to contribute, please run the style checker, as shown below, and fix the reported issues before sending a pull request:
npm run lint
In order to test Hazelcast Node.js client locally, you will need the following:
- Java 6 or newer
- Maven
Following command starts the tests:
npm test
Test script automatically downloads hazelcast-remote-controller and Hazelcast IMDG. The script uses Maven to download those.
You can use the following channels for your questions and development/usage issues:
- This repository by opening an issue.
- Hazelcast Node.js client channel on Gitter:
- Our Google Groups directory: https://groups.google.com/forum/#!forum/hazelcast
- Stack Overflow: https://stackoverflow.com/questions/tagged/hazelcast
Besides your development contributions as explained in the Development and Testing chapter above, you can always open a pull request on this repository for your other requests such as documentation changes.
Copyright (c) 2008-2018, Hazelcast, Inc. All Rights Reserved.
Visit www.hazelcast.com for more information.