org.alfresco.repo.transaction

Class RetryingTransactionHelper

java.lang.Object

org.alfresco.repo.transaction.RetryingTransactionHelper

@AlfrescoPublicApi
public class RetryingTransactionHelper
extends Object

A helper that runs a unit of work inside a UserTransaction, transparently retrying the unit of work if the cause of failure is an optimistic locking or deadlock condition.

Defaults:

• maxRetries: 20
• minRetryWaitMs: 100
• maxRetryWaitMs: 2000
• retryWaitIncrementMs: 100

To get details of 'why' transactions are retried use the following log level:
Summary: log4j.logger.org.alfresco.repo.transaction.RetryingTransactionHelper=INFO
Details: log4j.logger.org.alfresco.repo.transaction.RetryingTransactionHelper=DEBUG

Author:

Derek Hulley

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static interface	RetryingTransactionHelper.RetryingTransactionCallback<Result> Callback interface

Field Summary

Fields

Modifier and Type	Field and Description
static Class[]	RETRY_EXCEPTIONS Exceptions that trigger retries.

Constructor Summary

Constructors

Constructor and Description
RetryingTransactionHelper() Default constructor.

Method Summary

Modifier and Type	Method and Description
<R> R	doInTransaction(RetryingTransactionHelper.RetryingTransactionCallback<R> cb) Execute a callback in a transaction until it succeeds, fails because of an error not the result of an optimistic locking failure, or a deadlock loser failure, or until a maximum number of retries have been attempted.
<R> R	doInTransaction(RetryingTransactionHelper.RetryingTransactionCallback<R> cb, boolean readOnly) Execute a callback in a transaction until it succeeds, fails because of an error not the result of an optimistic locking failure, or a deadlock loser failure, or until a maximum number of retries have been attempted.
<R> R	doInTransaction(RetryingTransactionHelper.RetryingTransactionCallback<R> cb, boolean readOnly, boolean requiresNew) Execute a callback in a transaction until it succeeds, fails because of an error not the result of an optimistic locking failure, or a deadlock loser failure, or until a maximum number of retries have been attempted.
static Throwable	extractRetryCause(Throwable cause) Sometimes, the exception means retry and sometimes not.
static UserTransaction	getActiveUserTransaction() Utility method to get the active transaction.
void	setExtraExceptions(List<Class<?>> extraExceptions) Set the list of extra exceptions that should be retried
void	setForceWritable(boolean forceWritable) Override to allow the transactions to be writable regardless of the system read-only mode.
void	setMaxExecutionMs(long maxExecutionMs)
void	setMaxRetries(int maxRetries) Set the maximimum number of retries.
void	setMaxRetryWaitMs(int maxRetryWaitMs)
void	setMinRetryWaitMs(int minRetryWaitMs)
void	setReadOnly(boolean readOnly) Set whether this helper only supports read transactions.
void	setRetryWaitIncrementMs(int retryWaitIncrementMs)
void	setTransactionService(TransactionService service) Set the TransactionService.

Methods inherited from class java.lang.Object

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

Field Detail

RETRY_EXCEPTIONS

public static final Class[] RETRY_EXCEPTIONS

Exceptions that trigger retries.

Constructor Detail

RetryingTransactionHelper

public RetryingTransactionHelper()

Default constructor.

Method Detail

setTransactionService

public void setTransactionService(TransactionService service)

Set the TransactionService.

setMaxRetries

public void setMaxRetries(int maxRetries)

Set the maximimum number of retries. -1 for infinity.

setMinRetryWaitMs

public void setMinRetryWaitMs(int minRetryWaitMs)

setMaxRetryWaitMs

public void setMaxRetryWaitMs(int maxRetryWaitMs)

setRetryWaitIncrementMs

public void setRetryWaitIncrementMs(int retryWaitIncrementMs)

setMaxExecutionMs

public void setMaxExecutionMs(long maxExecutionMs)

setReadOnly

public void setReadOnly(boolean readOnly)

Set whether this helper only supports read transactions.

setForceWritable

public void setForceWritable(boolean forceWritable)

Override to allow the transactions to be writable regardless of the system read-only mode.

NOTE: This method may not be used to circumvent the Alfresco License policy.

Parameters:

forceWritable - true to force transactions to be writable regardless of system read-only mode

setExtraExceptions

public void setExtraExceptions(List<Class<?>> extraExceptions)

Set the list of extra exceptions that should be retried

doInTransaction

public <R> R doInTransaction(RetryingTransactionHelper.RetryingTransactionCallback<R> cb)

Execute a callback in a transaction until it succeeds, fails because of an error not the result of an optimistic locking failure, or a deadlock loser failure, or until a maximum number of retries have been attempted.

If there is already an active transaction, then the callback is merely executed and any retry logic is left to the caller. The transaction will attempt to be read-write.

Parameters:

cb - The callback containing the unit of work.

Returns:

Returns the result of the unit of work.

Throws:

RuntimeException - all checked exceptions are converted

doInTransaction

public <R> R doInTransaction(RetryingTransactionHelper.RetryingTransactionCallback<R> cb,
                             boolean readOnly)

Execute a callback in a transaction until it succeeds, fails because of an error not the result of an optimistic locking failure, or a deadlock loser failure, or until a maximum number of retries have been attempted.

If there is already an active transaction, then the callback is merely executed and any retry logic is left to the caller.

Parameters:

cb - The callback containing the unit of work.

readOnly - Whether this is a read only transaction.

Returns:

Returns the result of the unit of work.

Throws:

RuntimeException - all checked exceptions are converted

doInTransaction

public <R> R doInTransaction(RetryingTransactionHelper.RetryingTransactionCallback<R> cb,
                             boolean readOnly,
                             boolean requiresNew)

Execute a callback in a transaction until it succeeds, fails because of an error not the result of an optimistic locking failure, or a deadlock loser failure, or until a maximum number of retries have been attempted.

It is possible to force a new transaction to be created or to partake in any existing transaction.

Parameters:

cb - The callback containing the unit of work.

readOnly - Whether this is a read only transaction.

requiresNew - true to force a new transaction or false to partake in any existing transaction.

Returns:

Returns the result of the unit of work.

Throws:

RuntimeException - all checked exceptions are converted

extractRetryCause

public static Throwable extractRetryCause(Throwable cause)

Sometimes, the exception means retry and sometimes not. The stack of exceptions is also checked for any occurence of DoNotRetryException and, if found, nothing is returned.

Parameters:

cause - the cause to examine

Returns:

Returns the original cause if it is a valid retry cause, otherwise null

getActiveUserTransaction

public static UserTransaction getActiveUserTransaction()

Utility method to get the active transaction. The transaction status can be queried and marked for rollback.

NOTE: Any attempt to actually commit or rollback the transaction will cause failures.

Returns:

Returns the currently active user transaction or null if there isn't one.