Package com.sodius.oslc.server.concurrent.lock

Class AbstractLockExecutor<T>

java.lang.Object
com.sodius.oslc.server.concurrent.lock.AbstractLockExecutor<T>
Type Parameters:
T - the lock object type
All Implemented Interfaces:
LockExecutor, Executor
public abstract class AbstractLockExecutor<T> extends Object implements LockExecutor
An executor that uses a singleton lock object to ensure runnable instances are executed sequentially. This singleton object may be persisted in a database to be accessible across multiple JVMs.

For an alternative lock executor with file lock, see FileLockExecutor.

The executor uses a lock cache in case the runnable instances make subsequent calls to it, so the children commands dispose of the already acquired lock. It has optional parameters:

  • lockOperationInterval: time between lock operations retries in milliseconds
  • lockAcquisitionMaxRetries: max number of retries for lock acquisition
  • lockReleaseMaxRetries: max number of retries for lock release
  • lockMaxAge: maximum lock age in seconds before considering the lock as dead
Since:
1.12.0

  • Constructor Summary

    Constructors
    Modifier
    Constructor
    Description
    protected
    AbstractLockExecutor()
    Builds a Lock executor with a fixed interval of 100 milliseconds between retries, unlimited number of lock acquisition and release retries, and undefined lock max age.
    protected
    AbstractLockExecutor(int lockOperationInterval, int lockAcquisitionMaxRetries, int lockReleaseMaxRetries, int lockMaxAge)
    Builds a Lock executor with a fixed interval between retries, fixed numbers of retries, and a lock max age.

  • Method Summary

    Modifier and Type
    Method
    Description
    protected abstract Optional<T>
    acquireLock()
    Attempts to obtain a lock.
    <V> V
    execute(Callable<V> command)
    Executes the given task and returns its computed result, with the guarantee no other task for the same lock can run concurrently.
    protected abstract long
    getLockAge(T lock)
    Returns the lock age.
    protected abstract String
    getLockName()
    Returns the lock name to be displayed in logs.
    protected abstract Optional<T>
    queryLock()
    Queries an existing lock.
    protected abstract void
    releaseLock(T lock)
    Releases the lock.

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

    Methods inherited from interface com.sodius.oslc.server.concurrent.lock.LockExecutor

    execute

  • Constructor Details

    • AbstractLockExecutor

      protected AbstractLockExecutor()
      Builds a Lock executor with a fixed interval of 100 milliseconds between retries, unlimited number of lock acquisition and release retries, and undefined lock max age.

    • AbstractLockExecutor

      protected AbstractLockExecutor(int lockOperationInterval, int lockAcquisitionMaxRetries, int lockReleaseMaxRetries, int lockMaxAge)
      Builds a Lock executor with a fixed interval between retries, fixed numbers of retries, and a lock max age.
      Parameters:
      lockOperationInterval - interval in milliseconds between lock operation retries
      lockAcquisitionMaxRetries - the max number of lock acquisition retries
      lockReleaseMaxRetries - the max number of lock release retries
      lockMaxAge - the lock maximum age in seconds

  • Method Details

    • execute

      public <V> V execute(Callable<V> command) throws Exception
      Description copied from interface: LockExecutor
      Executes the given task and returns its computed result, with the guarantee no other task for the same lock can run concurrently.

      The task is expected to be very lightweight and short-running, so that it does't block for too long other concurrent requests.

      Specified by:
      execute in interface LockExecutor
      Type Parameters:
      V - the result type of method call
      Parameters:
      command - the runnable task
      Returns:
      the computed result
      Throws:
      Exception - if unable to compute a result. The exception is a CompletionException if the task is either interrupted or the timeout to acquire the lock expires.

    • queryLock

      protected abstract Optional<T> queryLock()
      Queries an existing lock. Returns empty if the lock is not found or an exception happens.
      Returns:
      an optional lock

    • getLockName

      protected abstract String getLockName()
      Returns the lock name to be displayed in logs.
      Returns:
      lock name

    • getLockAge

      protected abstract long getLockAge(T lock)
      Returns the lock age.
      Parameters:
      lock - the lock
      Returns:
      lock age in milliseconds

    • releaseLock

      protected abstract void releaseLock(T lock) throws LockException
      Releases the lock. If a not handled exception occurs, it must be thrown as a wrapped lock exception.
      Parameters:
      lock - the lock to release
      Throws:
      LockException - if something fails during the lock release

    • acquireLock

      protected abstract Optional<T> acquireLock() throws LockException
      Attempts to obtain a lock. If none is available, returns empty. If a not handled exception occurs, it must be thrown as a wrapped lock exception.
      Returns:
      an optional lock
      Throws:
      LockException - if something fails during the lock acquisition