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Named Locks using Hazelcast

This module implement named locks using Hazelcast. It provides two implementations, using members or clients and rely on Hazelcast ISemaphore instances.

Out of the box “hazelcast” (distributed) named lock implementations are the following:

  • semaphore-hazelcast implemented in org.eclipse.aether.named.hazelcast.HazelcastCPSemaphoreNamedLockFactory. Full Hazelcast member is used here.
  • semaphore-hazelcast-client implemented in org.eclipse.aether.named.hazelcast.HazelcastClientCPSemaphoreNamedLockFactory This implementation uses Hazelcast Client, so existing Hazelcast cluster to connect to is a requirement.

The semaphore name prefix is maven:resolver: and pre-configuring semaphores in Hazelcast is a must. The Hazelcast configuration must have the following entry:

  • Name prefix: maven:resolver: (use pattern matching configuration)
  • JDK compatible: true
  • Permit count: Integer.MAX_VALUE (value 2147483647)

Example Hazelcast XML relevant snippet:

    <cp-subsystem>
        <semaphores>
            <semaphore>
                <name>maven:resolver:*</name>
                <jdk-compatible>true</jdk-compatible>
                <initial-permits>2147483647</initial-permits>
            </semaphore>
        </semaphores>
    </cp-subsystem>

Without this configuration present, this library will not work.

Open Issues/Notes

  • The furnace-maven-plugin does not work this implementation because it uses ServiceLocator instead of dependency injection.

Open Issues/Notes for Maven Resolver integrators

To use this implementation within your project, depending on how you integrate, you have the following options:

  • If you use Sisu DI, then all you need is to provide this module (and Hazelcast JAR) on classpath, and you are done.
  • If you use Guice, you need to add this module (and its dependencies) upfront to classpath, and bind them explicitly.
  • If you use ServiceLocator, be aware it is deprecated, and you should move away from it. In this case, simplest is to roll your own “bootstrap” class that does pretty much same thing as ServiceLocator was, and extend it to instantiate these components as well.

Installation/Testing

  • Copy the following JARs from Maven Central to ${maven.home}/lib/ext/:
  • Configure Hazelcast instance with ${maven.conf}/hazelcast.xml or ${maven.conf}/hazelcast-client.xml (if client used). See Hazelcast documentation, default Hazelcast configuration discovery is being used.
  • Now start a multithreaded Maven build on your project and make sure NamedSyncContextFactory is being used.