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Named Locks

Named locks are essentially locks that are assigned to some given (opaque) ID. If you work with multiple resources that each can have unique ID assigned (i.e., file with an absolute path, some entities with unique ID), then you can use named locks to make sure they are being protected from concurrent read and write actions.

Named locks provide support classes for implementations, and provide out of the box seven named lock implementations and three name mappers.

Out of the box, “local” (local to JVM) named lock implementations are the following:

  • rwlock-local implemented in org.eclipse.aether.named.providers.LocalReadWriteLockNamedLockFactory that uses JVM java.util.concurrent.locks.ReentrantReadWriteLock.
  • semaphore-local implemented in org.eclipse.aether.named.providers.LocalSemaphoreNamedLockFactory that uses JVM java.util.concurrent.Semaphore.
  • file-lock implemented in org.eclipse.aether.named.providers.FileLockNamedLockFactory that uses JVM java.nio.channels.FileLock.
  • noop implemented in org.eclipse.aether.named.providers.NoopNamedLockFactory that uses no locking.

Out of the box, “distributed” named lock implementations are the following (separate modules which require additional dependencies):

  • rwlock-redisson implemented in org.eclipse.aether.named.redisson.RedissonReadWriteLockNamedLockFactory.
  • semaphore-redisson implemented in org.eclipse.aether.named.redisson.RedissonSemaphoreNamedLockFactory.
  • semaphore-hazelcast-client implemented in org.eclipse.aether.named.hazelcast.HazelcastClientCPSemaphoreNamedLockFactory.
  • semaphore-hazelcast implemented in org.eclipse.aether.named.hazelcast.HazelcastCPSemaphoreNamedLockFactory.

Local named locks are only suited within one JVM with a multithreaded build. Sharing a local repository between multiple Maven processes (i.e., on a busy CI server) requires a distributed named lock!

The aforementioned (opaque) IDs need to be mapped from artifacts and metadata.

Out of the box, name mapper implementations are the following:

  • static implemented in org.eclipse.aether.internal.impl.synccontext.named.StaticNameMapper.
  • gav implemented in org.eclipse.aether.internal.impl.synccontext.named.GAVNameMapper.
  • discriminating implemented in org.eclipse.aether.internal.impl.synccontext.named.DiscriminatingNameMapper.
  • file-gav implemented in org.eclipse.aether.internal.impl.synccontext.named.FileGAVNameMapper.