Consul based discovery strategy SPI for Hazelcast enabled applications
Latest commit db4514f Nov 7, 2016 @bitsofinfo release bump


Build Status

Provides a Consul based discovery strategy for Hazlecast 3.6+ enabled applications. This is an easy to configure plug-and-play Hazlecast DiscoveryStrategy that will optionally register each of your Hazelcast instances with Consul and enable Hazelcast nodes to dynamically discover one another via Consul.

Diagram of hazelcast consul discovery strategy


This is release candidate code, tested against Hazelcast 3.6-EA+ through 3.6.x Stable releases.


  • MASTER - in progress, this README refers to what is in the master tag. Switch to relevant RELEASE tag above to see that versions README

  • 1.0-RC6: Fix [#12], consul-client 0.13.2 upgrade, fix base64 Java 8 issue. Tested against Hazelcast 3.6-EA+ through 3.7+ Stable releases

  • 1.0-RC5: Upgrade to latest consul-client #11 Tested against Hazelcast 3.6-EA+ through 3.6.4+ Stable releases

  • 1.0-RC4: Adds support for TCP/HTTP checks #3 Tested against Hazelcast 3.6-EA+ through 3.6 Stable releases

  • 1.0-RC3: Adds support for TLS #2 and Consul ACLs #4 Tested against Hazelcast 3.6-EA+ through 3.6 Stable releases

  • 1.0-RC2: Tested against Hazelcast 3.6-EA+ through 3.6 Stable releases

  • 1.0-RC1: Tested against Hazelcast 3.6-EA+ through 3.6-RC1 Stable releases



To use this discovery strategy in your Maven or Gradle project use the dependency samples below.


repositories {

dependencies {
    compile 'org.bitsofinfo:hazelcast-consul-discovery-spi:1.0-RC6'

    // include your preferred implementation
    // (for the OrbitzWorldwide/consul-client dependency)
    // for example below:
    compile 'org.apache.cxf:cxf-rt-rs-client:3.0.3'
    compile 'org.apache.cxf:cxf-rt-transports-http-hc:3.0.3'



    <!-- include your preferred
         (for the dependency)
         implementation - see gradle example above



  • Supports two modes of operation:

    • Read-write: peer discovery and registration of a hazelcast instance without a local Consul agent (self registration)
    • Read-only: peer discovery only with an existing Consul agent setup (no registration by the strategy itself)
  • If you don't want to use the built in Consul registration, just specify the DoNothingRegistrator (see below) in your hazelcast discovery-strategy XML config. This will require you to run your own Consul agent that defines the hazelcast service.

  • If using self-registration, either LocalDiscoveryNodeRegistrator or ExplicitIpPortRegistrator which additionally support:

    • Automatic registration of the hazelcast instance with Consul
    • Custom Consul health-check script/interval to validate Hazelcast instance healthly
    • Control which IP is published as the service-address with Consul
    • Configurable discovery delay
    • Automatic Consul de-registration of instance via ShutdownHook


  • Ensure your project has the hazelcast-consul-discovery-spi artifact dependency declared in your maven pom or gradle build file as described above. Or build the jar yourself and ensure the jar is in your project's classpath.

  • Have Consul running and available somewhere on your network, start it such as:

consul agent -server -bootstrap-expect 1 -data-dir /tmp/consul -config-dir /path/to/consul.d/ -ui-dir /path/to/consul-web-ui
  • Configure your hazelcast.xml configuration file to use the ConsulDiscoveryStrategy (similar to the below): See hazelcast-consul-discovery-spi-example.xml for a full example with documentation of options.

  • Launch your hazelcast instances, configured with the Consul discovery-strategy similar to the below: see example.

  <port auto-increment="true">5701</port>

    <multicast enabled="false"/>
    <aws enabled="false"/>
    <tcp-ip enabled="false" />

       <discovery-strategy enabled="true"

              <property name="consul-host">localhost</property>
              <property name="consul-port">8500</property>
              <property name="consul-service-name">hz-discovery-test-cluster</property>
              <property name="consul-healthy-only">true</property>
              <property name="consul-service-tags">hazelcast, test1</property>
              <property name="consul-discovery-delay-ms">10000</property>

              <property name="consul-acl-token"></property>
              <property name="consul-ssl-enabled">false</property>
              <property name="consul-ssl-server-cert-file-path"></property>
              <property name="consul-ssl-server-cert-base64"></property>
              <property name="consul-ssl-server-hostname-verify">true</property>

              <property name="consul-registrator">org.bitsofinfo.hazelcast.discovery.consul.LocalDiscoveryNodeRegistrator</property>
              <property name="consul-registrator-config"><![CDATA[
                          "healthCheckScript":"exec 6<>/dev/tcp/#MYIP/#MYPORT || (exit 3)",

  • Once nodes are joined you can query Consul to see the auto-registration of hazelcast instances works, the service-id's generated etc

curl http://localhost:8500/v1/catalog/services


curl http://localhost:8500/v1/catalog/service/hz-discovery-test-cluster


Building from source

  • From the root of this project, build a Jar : ./gradlew assemble

  • Include the built jar artifact located at build/libs/hazelcast-consul-discovery-spi-[VERSION].jar in your hazelcast project

  • If not already present in your hazelcast application's Maven (pom.xml) or Gradle (build.gradle) dependencies section; ensure that these dependencies are present (versions may vary as appropriate):

compile group: 'com.orbitz.consul', name: 'consul-client', version:'0.9.16'
compile group: 'org.apache.cxf', name:'cxf-rt-rs-client', version:'3.0.3'
compile group: 'org.apache.cxf', name:'cxf-rt-transports-http-hc', version:'3.0.3'

Consul UI example

Showing LocalDiscoveryNodeRegistrator configured hazelcast services with health-checks

Diagram of consul ui


It may also help you to understand the functionality by checking out and running the unit-tests located at src/test/java. BE SURE TO READ the comments in the test source files as some of the tests require you to setup your local Consul and edit certain files.

From the command line you can run TestExplicitIpPortRegistrator and TestLocalDiscoveryNodeRegistrator unit-tests by invoking the runTests task using gradlew that runs both tests and displays the result on the console.

$ ./gradlew runTests

The task above will display output indicating the test has started and whether the test has passed or failed.

Sample output for passing test:
org.bitsofinfo.hazelcast.discovery.consul.TestExplicitIpPortRegistrator > testExplicitIpPortRegistrator STARTED

org.bitsofinfo.hazelcast.discovery.consul.TestExplicitIpPortRegistrator > testExplicitIpPortRegistrator PASSED
Sample output for failing test:
org.bitsofinfo.hazelcast.discovery.consul.TestDoNothingRegistrator > testDoNothingRegistrator STARTED

org.bitsofinfo.hazelcast.discovery.consul.TestDoNothingRegistrator > testDoNothingRegistrator FAILED
    java.lang.AssertionError at

To run individual unit-test, use the unitTest.single argument to provide the unit-test you would like to run. The command below runs the unit test for TestDoNothingRegistrator

$ ./gradlew -DunitTest.single=TestDoNothingRegistrator unitTest
Note on running TestDoNothingRegistrator unit-test

The TestDoNothingRegistrator unit-test should be run separately using the unitTest.single argument as demonstrated above as it requires you to register a service with your local consul with 5 nodes/instances. Please CAREFULLY READ the comments in to see how this test should be run.

Passing optional parameters to unit-tests

The following parameters can be passed with the -D option when invoking the tests

-DconsulPort=(some port)
-DconsulHost=(some host)
-DconsulAclToken=(some ACL token if the server requires it)
-DconsulSslEnabled=(true | false)
-DconsulSslServerCertBase64=(base64 encoded cert string)
-DconsulHealthCheckProvider=(org.bitsofinfo.hazelcast.discovery.consul.ScriptHealthCheckBuilder | org.bitsofinfo.hazelcast.discovery.consul.HttpHealthCheckBuilder)

Related info


  • Ensure all configuration tweakable via -D system properties


Containerization (Docker) notes

This library may also be helpful to you: docker-discovery-registrator-consul

One of the main drivers for coding this module was for Hazelcast applications that were deployed as Docker containers that would need to automatically register themselves with Consul for higher level cluster orchestration of the cluster.

If you are deploying your Hazelcast application as a Docker container, one helpful tip is that you will want to avoid hardwired configuration in the hazelcast XML config, but rather have your Docker container take startup arguments that would be translated to -D system properties on startup. Convienently Hazelcast can consume these JVM system properties and replace variable placeholders in the XML config. See this documentation for examples:

Specifically when using this discovery strategy and Docker, it may be useful for you to use the ExplicitIpPortRegistrator ConsulRegistrator instead of the LocalDiscoveryNodeRegistrator as the latter relies on hazelcast to determine its IP/PORT and this may end up being the local container IP, and not the Docker host IP, leading to a situation where a unreachable IP/PORT combination is published to Consul.

Example: excerpt from explicitIpPortRegistrator-example.xml

Start your hazelcast app such as with the below, this would assume that hazelcast is actually reachable via this configuration via your Docker host and the port mappings that were specified on docker run. (i.e. the IP below would be your docker host/port that is mapped to the actual hazelcast app container and port it exposes for hazelcast).

This library may also be helpful to you: docker-discovery-registrator-consul

See this Docker issue for related info on detecting mapped ports/ip from within a container

java -jar myHzApp.jar -DregisterWithIpAddress=<dockerHostIp> -DregisterWithPort=<mappedContainerPortOnDockerHost> ....

<property name="consul-registrator-config"><![CDATA[
        "healthCheckScript":"exec 6<>/dev/tcp/#MYIP/#MYPORT || (exit 3)",

Consul health-check notes

You should see this in your Consul agent monitor when the health-check scripts are running:

> consul monitor --log-level trace

2015/11/20 11:21:39 [DEBUG] agent: check 'service:hz-discovery-test-cluster-' script 'exec 6<>/dev/tcp/ || (exit 3)' output:
2015/11/20 11:21:39 [DEBUG] agent: Check 'service:hz-discovery-test-cluster-' is passing

You will see something like these warnings logged when the health-check script interrogates the hazelcast port and does nothing. You are free to monitor the services any way you wish, or not at all by omitting the healthCheckScript JSON property; see See hazelcast-consul-discovery-spi-example.xml for an example.

Nov 20, 2015 6:57:50 PM com.hazelcast.nio.tcp.SocketAcceptorThread
INFO: []:5701 [hazelcast-consul-discovery] [3.6] Accepting socket connection from /
Nov 20, 2015 6:57:50 PM com.hazelcast.nio.tcp.TcpIpConnectionManager
INFO: []:5701 [hazelcast-consul-discovery] [3.6] Established socket connection between / and /
Nov 20, 2015 6:57:50 PM com.hazelcast.nio.tcp.nonblocking.NonBlockingSocketWriter
WARNING: []:5701 [hazelcast-consul-discovery] [3.6] SocketWriter is not set, creating SocketWriter with CLUSTER protocol!
Nov 20, 2015 6:57:50 PM com.hazelcast.nio.tcp.TcpIpConnection
INFO: []:5701 [hazelcast-consul-discovery] [3.6] Connection [/] lost. Reason:[Could not read protocol type!]