Message queueing system with an actor-based Scala and Amazon SQS-compatible interfaces. Runs stand-alone or embedded.
Scala
Adam Warski
Latest commit 40162c2 Aug 13, 2018

README.md

ElasticMQ

tl;dr

  • in-memory message queue system
  • runs stand-alone (download), via Docker or embedded
  • Amazon SQS-compatible interface
  • fully asynchronous implementation, no blocking calls

Created and maintained by SoftwareMill logo

Summary

ElasticMQ is a message queue system, offering an actor-based Scala and an SQS-compatible REST (query) interface.

ElasticMQ follows the semantics of SQS. Messages are received by polling the queue. When a message is received, it is blocked for a specified amount of time (the visibility timeout). If the message isn't deleted during that time, it will be again available for delivery. Moreover, queues and messages can be configured to always deliver messages with a delay.

The focus in SQS (and ElasticMQ) is to make sure that the messages are delivered. It may happen, however, that a message is delivered twice (if, for example, a client dies after receiving a message and processing it, but before deleting). That's why clients of ElasticMQ (and Amazon SQS) should be idempotent.

As ElasticMQ implements a subset of the SQS query (REST) interface, it is a great SQS alternative both for testing purposes (ElasticMQ is easily embeddable) and for creating systems which work both within and outside of the Amazon infrastructure.

The future will most probably bring even more exciting features :).

Community

Installation: stand-alone

You can download the stand-alone distribution here: https://s3/.../elasticmq-server-0.14.5.jar

Java 8 or above is required for running the server.

Simply run the jar and you should get a working server, which binds to localhost:9324:

java -jar elasticmq-server-0.14.5.jar

ElasticMQ uses Typesafe Config for configuration. To specify custom configuration values, create a file (e.g. custom.conf), fill it in with the desired values, and pass it to the server:

java -Dconfig.file=custom.conf -jar elasticmq-server-0.14.5.jar

The config file may contain any configuration for Akka and ElasticMQ. Current ElasticMQ configuration values are:

include classpath("application.conf")

// What is the outside visible address of this ElasticMQ node
// Used to create the queue URL (may be different from bind address!)
node-address {
    protocol = http
    host = localhost
    port = 9324
    context-path = ""
}

rest-sqs {
    enabled = true
    bind-port = 9324
    bind-hostname = "0.0.0.0"
    // Possible values: relaxed, strict
    sqs-limits = strict
}

// Should the node-address be generated from the bind port/hostname
// Set this to true e.g. when assigning port automatically by using port 0.
generate-node-address = false

queues {
    // See next section
}

You can also provide an alternative Logback configuration file (the default is configured to log INFO logs and above to the console):

java -Dlogback.configurationFile=my_logback.xml -jar elasticmq-server-0.14.5.jar

How are queue URLs created

Some of the responses include a queue URL. By default the urls will use http://localhost:9324 as the base URL. To customize, you should properly set the protocol/host/port/context in the node-address setting (see above).

You can also set node-address.host to a special value, "*", which will cause any queue URLs created during a request to use the path of the incoming request. This might be useful e.g. in containerized (Docker) deployments.

Note that changing the bind-port and bind-hostname settings does not affect the queue URLs in any way unless generate-node-address is true. In that case, the bind host/port are used to create the node address. This is useful when the port should be automatically assigned (use port 0 in such case, the selected port will be visible in the logs).

Automatically creating queues on startup

Queues can be automatically created on startup by providing appropriate configuration:

The queues are specified in a custom configuration file. For example, create a custom.conf file with the following:

include classpath("application.conf")

queues {
    queue1 {
        defaultVisibilityTimeout = 10 seconds
        delay = 5 seconds
        receiveMessageWait = 0 seconds
        deadLettersQueue {
            name = "queue1-dead-letters"
            maxReceiveCount = 3 // from 1 to 1000
        }
        fifo = false
        contentBasedDeduplication = false
        copyTo = "audit-queue-name"
        moveTo = "redirect-queue-name"
        tags {
            tag1 = "tagged1"
            tag2 = "tagged2"
        }
    }
    queue1-dead-letters { }
    audit-queue-name { }
    redirect-queue-name { }
}

All attributes are optional (except name and maxReceiveCount when a deadLettersQueue is defined). copyTo and moveTo attributes allow to achieve behavior that might be useful primarily for integration testing scenarios - all messages could be either duplicated (using copyTo attribute) or redirected (using moveTo attribute) to another queue.

Starting an embedded ElasticMQ server with an SQS interface

val server = SQSRestServerBuilder.start()
// ... use ...
server.stopAndWait()

If you need to bind to a different host/port, there are configuration methods on the builder:

val server = SQSRestServerBuilder.withPort(9325).withInterface("localhost").start()
// ... use ...
server.stopAndWait()

You can also set a dynamic port with a port value of 0 or by using the method withDynamicPort. To retrieve the port (and other configuration) when using a dynamic port value you can access the server via waitUntilStarted for example:

val server = SQSRestServerBuilder.withDynamicPort().start()
server.waitUntilStarted().localAddress().getPort()

You can also provide a custom ActorSystem; for details see the javadocs.

Embedded ElasticMQ can be used from any JVM-based language (Java, Scala, etc.).

Using the Amazon Java SDK to access an ElasticMQ Server

To use Amazon Java SDK as an interface to an ElasticMQ server you just need to change the endpoint:

String endpoint = "http://localhost:9324";
String region = "elasticmq";
String accessKey = "x";
String secretKey = "x";
AmazonSQS client = AmazonSQSClientBuilder.standard()
    .withCredentials(new AWSStaticCredentialsProvider(new BasicAWSCredentials(accessKey, secretKey)))
    .withEndpointConfiguration(new AwsClientBuilder.EndpointConfiguration(endpoint, region))
    .build();

The endpoint value should be the same address as the NodeAddress provided as an argument to SQSRestServerBuilder or in the configuration file.

The rest-sqs-testing-amazon-java-sdk module contains some more usage examples.

Using the Amazon boto (Python) to access an ElasticMQ Server

To use Amazon boto as an interface to an ElasticMQ server you set up the connection using:

region = boto.sqs.regioninfo.RegionInfo(name='elasticmq',
                                        endpoint=sqs_endpoint)
conn = boto.connect_sqs(aws_access_key_id='x',
                        aws_secret_access_key='x',
                        is_secure=False,
                        port=sqs_port,
                        region=region)

where sqs_endpoint and sqs_port are the host and port.

The boto3 interface is different:

client = boto3.resource('sqs',
                        endpoint_url='http://localhost:9324',
                        region_name='elasticmq',
                        aws_secret_access_key='x',
                        aws_access_key_id='x',
                        use_ssl=False)
queue = client.get_queue_by_name(QueueName='queue1')

ElasticqMQ via Docker

A Docker image is built on each release an pushed as softwaremill/elasticmq.

The image uses default configuration. Custom configuration can be provided (e.g. to change the port, or create queues on startup) by creating a custom configuration file (see above) and using it when running the container:

docker run -v `pwd`/custom.conf:/opt/elasticmq.conf softwaremill/elasticmq

ElasticMQ dependencies in SBT

// Scala 2.12 and 2.11
val elasticmqSqs        = "org.elasticmq" %% "elasticmq-rest-sqs" % "0.14.5"

If you don't want the SQS interface, but just use the actors directly, you can add a dependency only to the core module:

val elasticmqCore       = "org.elasticmq" %% "elasticmq-core" % "0.14.5"

If you want to use a snapshot version, you will need to add the https://oss.sonatype.org/content/repositories/snapshots/ repository to your configuration.

ElasticMQ dependencies in Maven

Dependencies:

<dependency>
    <groupId>org.elasticmq</groupId>
    <artifactId>elasticmq-rest-sqs_2.11</artifactId>
    <version>0.14.5</version>
</dependency>

If you want to use a snapshot version, you will need to add the https://oss.sonatype.org/content/repositories/snapshots/ repository to your configuration.

Current versions

Stable: 0.14.5, 0.8.12

Development: 0.14.5-SNAPSHOT

Logging

ElasticMQ uses Slf4j for logging. By default no logger backend is included as a dependency, however Logback is recommended.

Performance

Tests done on a 2012 MBP, 2.6GHz, 16GB RAM, no replication. Throughput is in messages per second (messages are small).

Directly accessing the client:

Running test for [in-memory], iterations: 10, msgs in iteration: 100000, thread count: 1.
Overall in-memory throughput: 21326.054040

Running test for [in-memory], iterations: 10, msgs in iteration: 100000, thread count: 2.
Overall in-memory throughput: 26292.956117

Running test for [in-memory], iterations: 10, msgs in iteration: 100000, thread count: 10.
Overall in-memory throughput: 25591.155697

Through the SQS REST interface:

Running test for [rest-sqs + in-memory], iterations: 10, msgs in iteration: 1000, thread count: 20.
Overall rest-sqs + in-memory throughput: 2540.553587

Running test for [rest-sqs + in-memory], iterations: 10, msgs in iteration: 1000, thread count: 40.
Overall rest-sqs + in-memory throughput: 2600.002600

Note that both the client and the server were on the same machine.

Test class: org.elasticmq.performance.LocalPerformanceTest.

Building, running, and packaging

To build and run with debug (this will listen for a remote debugger on port 5005):

~/workspace/elasticmq $ sbt -jvm-debug 5005
> project elasticmq-server
> run

To build a jar-with-dependencies:

~/workspace/elasticmq $ sbt
> project elasticmq-server
> assembly

Tests and coverage

To run the tests:

~/workspace/elasticmq $ sbt test

To check the coverage reports:

~/workspace/elasticmq $ sbt
> coverage
> tests
> coverageReport
> coverageAggregate

Although it's mostly only the core project that is relevant for coverage testing, each project's report can be found in their target directory:

  • core/target/scala-2.12/scoverage-report/index.html
  • common-test/target/scala-2.12/scoverage-report/index.html
  • rest/rest-sqs/target/scala-2.12/scoverage-report/index.html
  • server/target/scala-2.12/scoverage-report/index.html

The aggregate report can be found at target/scala-2.12/scoverage-report/index.html

Technology

  • Core: Scala and Akka.
  • Rest server: Akka HTTP, a high-performance, asynchronous, REST/HTTP toolkit.
  • Testing the SQS interface: Amazon Java SDK; see the rest-sqs-testing-amazon-java-sdk module for the testsuite.