org.alfresco.repo.lock

Class JobLockServiceImpl

java.lang.Object

org.alfresco.repo.lock.JobLockServiceImpl

All Implemented Interfaces:

JobLockService

public class JobLockServiceImpl
extends Object
implements JobLockService

Since:

3.2

Author:

Derek Hulley

Nested Class Summary

Nested classes/interfaces inherited from interface org.alfresco.repo.lock.JobLockService

JobLockService.JobLockRefreshCallback

Constructor Summary

Constructors

Constructor and Description
JobLockServiceImpl()

Method Summary

Modifier and Type	Method and Description
String	getLock(org.alfresco.service.namespace.QName lockQName, long timeToLive) Take a manually-managed lock.
String	getLock(org.alfresco.service.namespace.QName lockQName, long timeToLive, JobLockService.JobLockRefreshCallback callback) Take a manually-managed lock and provide a callback to refresh it periodically.
String	getLock(org.alfresco.service.namespace.QName lockQName, long timeToLive, long retryWait, int retryCount) Take a manually-managed lock.
void	getTransactionalLock(org.alfresco.service.namespace.QName lockQName, long timeToLive) Take a transactionally-managed lock.
void	getTransactionalLock(org.alfresco.service.namespace.QName lockQName, long timeToLive, long retryWait, int retryCount) Take a transactionally-managed lock.
void	refreshLock(String lockToken, org.alfresco.service.namespace.QName lockQName, long timeToLive) Refresh the lock using a valid lock token.
void	refreshLock(String lockToken, org.alfresco.service.namespace.QName lockQName, long timeToLive, JobLockService.JobLockRefreshCallback callback) Provide a callback to refresh a lock using a valid lock token, pushing responsibility for regular lock refreshing onto the service implementation code.
void	releaseLock(String lockToken, org.alfresco.service.namespace.QName lockQName) Release the lock using a valid lock token.
boolean	releaseLockVerify(String lockToken, org.alfresco.service.namespace.QName lockQName) Release the lock using a valid lock token.
void	setDefaultRetryCount(int defaultRetryCount) Set the maximum number of attempts to make at getting a lock
void	setDefaultRetryWait(long defaultRetryWait) Set the default time to wait between attempts to acquire a lock
void	setLockDAO(LockDAO lockDAO) Set the lock DAO
void	setRetryingTransactionHelper(RetryingTransactionHelper retryingTransactionHelper) Set the helper that will handle low-level concurrency conditions i.e.
void	shutdown() Lifecycle method.

Methods inherited from class java.lang.Object

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

Constructor Detail

JobLockServiceImpl

public JobLockServiceImpl()

Method Detail

shutdown

public void shutdown()

Lifecycle method. This method should be called when the JobLockService is no longer required allowing proper clean up before disposing of the object.

This is mostly used to tell the thread pool to shut itself down so as to allow the JVM to terminate.

setLockDAO

public void setLockDAO(LockDAO lockDAO)

Set the lock DAO

setRetryingTransactionHelper

public void setRetryingTransactionHelper(RetryingTransactionHelper retryingTransactionHelper)

Set the helper that will handle low-level concurrency conditions i.e. that enforces optimistic locking and deals with stale state issues.

setDefaultRetryCount

public void setDefaultRetryCount(int defaultRetryCount)

Set the maximum number of attempts to make at getting a lock

Parameters:

defaultRetryCount - the number of attempts

setDefaultRetryWait

public void setDefaultRetryWait(long defaultRetryWait)

Set the default time to wait between attempts to acquire a lock

Parameters:

defaultRetryWait - the wait time in milliseconds

getTransactionalLock

public void getTransactionalLock(org.alfresco.service.namespace.QName lockQName,
                                 long timeToLive)

Take a transactionally-managed lock. This method can be called repeatedly to both initially acquire the lock as well as to maintain the lock. This method should be called repeatedly during the transaction to ensure that the lock remains refreshed. DO NOT use a long-lived lock to avoid calling this method at intervals; long-lived locks get left behind during server crashes, amongst other things.

The following rules apply to taking and releasing locks:
- Expired locks can be taken by any process
- Lock expiration does not prevent a lock from being refreshed or released
- Only locks that were manipulated using another token will cause failure

The locks are automatically released when the transaction is terminated.

Any failure to acquire the lock (after retries), refresh the lock or subsequently release the owned locks will invalidate the transaction and cause rollback.

Specified by:

getTransactionalLock in interface JobLockService

Parameters:

lockQName - the name of the lock to acquire

timeToLive - the time (in milliseconds) for the lock to remain valid. This value must not be larger than either the anticipated operation time or a server startup time. Typically, it should be a few seconds.

getTransactionalLock

public void getTransactionalLock(org.alfresco.service.namespace.QName lockQName,
                                 long timeToLive,
                                 long retryWait,
                                 int retryCount)

Take a transactionally-managed lock. This method can be called repeatedly to both initially acquire the lock as well as to maintain the lock. This method should be called repeatedly during the transaction to ensure that the lock remains refreshed. DO NOT use a long-lived lock to avoid calling this method at intervals; long-lived locks get left behind during server crashes, amongst other things.

The following rules apply to taking and releasing locks:
- Expired locks can be taken by any process
- Lock expiration does not prevent a lock from being refreshed or released
- Only locks that were manipulated using another token will cause failure

The locks are automatically released when the transaction is terminated.

Any failure to acquire the lock (after retries), refresh the lock or subsequently release the owned locks will invalidate the transaction and cause rollback.

If the lock cannot be immediately acquired, the process will wait and retry. Note that second and subsequent attempts to get the lock during a transaction cannot make use of retrying; the lock is actually being refreshed and will therefore never become valid if it doesn't refresh directly.

Specified by:

getTransactionalLock in interface JobLockService

Parameters:

lockQName - the name of the lock to acquire

timeToLive - the time (in milliseconds) for the lock to remain valid. This value must not be larger than either the anticipated operation time or a server startup time. Typically, it should be a few seconds.

retryWait - the time (in milliseconds) to wait before trying again

retryCount - the maximum number of times to attempt the lock acquisition

getLock

public String getLock(org.alfresco.service.namespace.QName lockQName,
                      long timeToLive)

Take a manually-managed lock. The lock current thread or transaction will not be tagged - the returned lock token must be used for further management of the lock.

No lock management is provided: the lock must be released manually or will only become available by expiry. No deadlock management is provided, either.

Specified by:

getLock in interface JobLockService

Parameters:

lockQName - the name of the lock to acquire

timeToLive - the time (in milliseconds) for the lock to remain valid. This value must not be larger than either the anticipated operation time or a server startup time. Typically, it should be a few seconds.

Returns:

Returns the newly-created lock token

See Also:

getLock(QName, long, long, int)

getLock

public String getLock(org.alfresco.service.namespace.QName lockQName,
                      long timeToLive,
                      long retryWait,
                      int retryCount)

Take a manually-managed lock. The lock current thread or transaction will not be tagged - the returned lock token must be used for further management of the lock.

No lock management is provided: the lock must be released manually or will only become available by expiry. No deadlock management is provided, either.

If the lock cannot be immediately acquired, the process will wait and retry.

Specified by:

getLock in interface JobLockService

Parameters:

lockQName - the name of the lock to acquire

timeToLive - the time (in milliseconds) for the lock to remain valid. This value must not be larger than either the anticipated operation time or a server startup time. Typically, it should be a few seconds.

retryWait - the time (in milliseconds) to wait before trying again

retryCount - the maximum number of times to attempt the lock acquisition

refreshLock

public void refreshLock(String lockToken,
                        org.alfresco.service.namespace.QName lockQName,
                        long timeToLive)

Refresh the lock using a valid lock token.

Specified by:

refreshLock in interface JobLockService

lockQName - the name of the previously-acquired lock

timeToLive - the time (in milliseconds) for the lock to remain valid

Throws:

LockAcquisitionException - on failure

getLock

public String getLock(org.alfresco.service.namespace.QName lockQName,
                      long timeToLive,
                      JobLockService.JobLockRefreshCallback callback)

Take a manually-managed lock and provide a callback to refresh it periodically. A convenience wrapper around JobLockService.getLock(QName,long) and JobLockService.refreshLock(String,QName,long,JobLockRefreshCallback).

Specified by:

getLock in interface JobLockService

Parameters:

lockQName - the name of the lock to acquire

timeToLive - the time (in milliseconds) for the lock to remain valid. This value must not be larger than either the anticipated operation time or a server startup time. Typically, it should be a few seconds.

callback - the object that will be called at intervals of timeToLive/2 (about)

Returns:

Returns the newly-created lock token, or null if callback not active.

refreshLock

public void refreshLock(String lockToken,
                        org.alfresco.service.namespace.QName lockQName,
                        long timeToLive,
                        JobLockService.JobLockRefreshCallback callback)

Provide a callback to refresh a lock using a valid lock token, pushing responsibility for regular lock refreshing onto the service implementation code. This method should only be called once for a given lock token to prevent unnecessary refreshing.

Since the lock is not actually refreshed by this method, there will be no LockAcquisitionException.

The TTL (time to live) will be divided by two and the result used to trigger a timer thread to initiate the callback. The first refresh will occur after TTL/2 and no significant work should be done between acquiring a lock and calling this method, to prevent expiration.

Specified by:

refreshLock in interface JobLockService

Parameters:

lockToken - the lock token returned when the lock was acquired

lockQName - the name of the previously-acquired lock

timeToLive - the time (in milliseconds) for the lock to remain valid

callback - the object that will be called at intervals of timeToLive/2 (about)

releaseLock

public void releaseLock(String lockToken,
                        org.alfresco.service.namespace.QName lockQName)

Release the lock using a valid lock token.

Specified by:

releaseLock in interface JobLockService

Parameters:

lockToken - the lock token returned when the lock was acquired

lockQName - the name of the previously-acquired lock

releaseLockVerify

public boolean releaseLockVerify(String lockToken,
                                 org.alfresco.service.namespace.QName lockQName)

Release the lock using a valid lock token. The lock can have been taken by another process (i.e. the lock token will no longer be valid); none of this will prevent the method from succeeding.

Specified by:

releaseLockVerify in interface JobLockService

Parameters:

lockToken - the lock token returned when the lock was acquired

lockQName - the name of the previously-acquired lock

Returns:

true if the lock was valid and released otherwise false if the lock was already held by another token