com.sleepycat.collections
Class TransactionRunner

java.lang.Object
  com.sleepycat.collections.TransactionRunner

public class TransactionRunner

extends Object

Starts a transaction, calls TransactionWorker.doWork(), and handles transaction retry and exceptions.

Field Summary

static int

DEFAULT_MAX_RETRIES The default maximum number of retries.

Constructor Summary

TransactionRunner(Environment env)
Creates a transaction runner for a given Berkeley DB environment.

TransactionRunner(Environment env, int maxRetries, TransactionConfig config)
Creates a transaction runner for a given Berkeley DB environment and with a given number of maximum retries.

Method Summary

boolean	getAllowNestedTransactions() Returns whether nested transactions will be created if run() is called when a transaction is already active for the current thread.
int	getMaxRetries() Returns the maximum number of retries that will be performed when deadlocks are detected.
TransactionConfig	getTransactionConfig() Returns the transaction configuration used for calling Environment.beginTransaction(com.sleepycat.db.Transaction, com.sleepycat.db.TransactionConfig).
void	run(TransactionWorker worker) Calls the TransactionWorker.doWork() method and, for transactional environments, begins and ends a transaction.
void	setAllowNestedTransactions(boolean allowNestedTxn) Changes whether nested transactions will be created if run() is called when a transaction is already active for the current thread.
void	setMaxRetries(int maxRetries) Changes the maximum number of retries that will be performed when deadlocks are detected.
void	setTransactionConfig(TransactionConfig config) Changes the transaction configuration used for calling Environment.beginTransaction(com.sleepycat.db.Transaction, com.sleepycat.db.TransactionConfig).

Methods inherited from class java.lang.Object

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

Field Detail

DEFAULT_MAX_RETRIES

public static final int DEFAULT_MAX_RETRIES

The default maximum number of retries.

See Also:

Constant Field Values

Constructor Detail

TransactionRunner

public TransactionRunner(Environment env)

Creates a transaction runner for a given Berkeley DB environment. The default maximum number of retries (DEFAULT_MAX_RETRIES) and a null (default) TransactionConfig will be used.

Parameters:

env - is the environment for running transactions.

TransactionRunner

public TransactionRunner(Environment env,
                         int maxRetries,
                         TransactionConfig config)

Creates a transaction runner for a given Berkeley DB environment and with a given number of maximum retries.

Parameters:

env - is the environment for running transactions.

maxRetries - is the maximum number of retries that will be performed when deadlocks are detected.

config - the transaction configuration used for calling Environment.beginTransaction(com.sleepycat.db.Transaction, com.sleepycat.db.TransactionConfig), or null to use the default configuration. The configuration object is not cloned, and any modifications to it will impact subsequent transactions.

Method Detail

getMaxRetries

public int getMaxRetries()

Returns the maximum number of retries that will be performed when deadlocks are detected.

setMaxRetries

public void setMaxRetries(int maxRetries)

Changes the maximum number of retries that will be performed when deadlocks are detected. Calling this method does not impact transactions already running.

getAllowNestedTransactions

public boolean getAllowNestedTransactions()

Returns whether nested transactions will be created if run() is called when a transaction is already active for the current thread. By default this property is false.

setAllowNestedTransactions

public void setAllowNestedTransactions(boolean allowNestedTxn)

Changes whether nested transactions will be created if run() is called when a transaction is already active for the current thread. Calling this method does not impact transactions already running.

getTransactionConfig

public TransactionConfig getTransactionConfig()

Returns the transaction configuration used for calling Environment.beginTransaction(com.sleepycat.db.Transaction, com.sleepycat.db.TransactionConfig).

If this property is null, the default configuration is used. The configuration object is not cloned, and any modifications to it will impact subsequent transactions.

Returns:

the transaction configuration.

setTransactionConfig

public void setTransactionConfig(TransactionConfig config)

Changes the transaction configuration used for calling Environment.beginTransaction(com.sleepycat.db.Transaction, com.sleepycat.db.TransactionConfig).

If this property is null, the default configuration is used. The configuration object is not cloned, and any modifications to it will impact subsequent transactions.

Parameters:

config - the transaction configuration.

run

public void run(TransactionWorker worker)
         throws DatabaseException,
                Exception

Calls the TransactionWorker.doWork() method and, for transactional environments, begins and ends a transaction. If the environment given is non-transactional, a transaction will not be used but the doWork() method will still be called.

In a transactional environment, a new transaction is started before calling doWork(). This will start a nested transaction if one is already active. If DeadlockException is thrown by doWork(), the transaction will be aborted and the process will be repeated up to the maximum number of retries specified. If another exception is thrown by doWork() or the maximum number of retries has occurred, the transaction will be aborted and the exception will be rethrown by this method. If no exception is thrown by doWork(), the transaction will be committed. This method will not attempt to commit or abort a transaction if it has already been committed or aborted by doWork().

Throws:

DeadlockException - when it is thrown by doWork() and the maximum number of retries has occurred. The transaction will have been aborted by this method.

Exception - when any other exception is thrown by doWork(). The exception will first be unwrapped by calling ExceptionUnwrapper.unwrap(java.lang.Exception). The transaction will have been aborted by this method.

DatabaseException