com.datastax.driver.core.policies

Class IdempotenceAwareRetryPolicy

java.lang.Object

com.datastax.driver.core.policies.IdempotenceAwareRetryPolicy

All Implemented Interfaces:

RetryPolicy

Direct Known Subclasses:

LoggingIdempotenceAwareRetryPolicy

public class IdempotenceAwareRetryPolicy
extends Object
implements RetryPolicy

A retry policy that avoids retrying non-idempotent statements.

In case of write timeouts or unexpected errors, this policy will always return RetryPolicy.RetryDecision.rethrow() if the statement is deemed non-idempotent (see isIdempotent(Statement)).

For all other cases, this policy delegates the decision to the child policy.

Nested Class Summary

Nested classes/interfaces inherited from interface com.datastax.driver.core.policies.RetryPolicy

RetryPolicy.RetryDecision

Constructor Summary

Constructors

Constructor and Description
IdempotenceAwareRetryPolicy(RetryPolicy childPolicy) Creates a new instance.

Method Summary

Modifier and Type	Method and Description
void	close() Gets invoked at cluster shutdown.
void	init(Cluster cluster) Gets invoked at cluster startup.
protected boolean	isIdempotent(Statement statement) Determines whether the given statement is idempotent or not.
RetryPolicy.RetryDecision	onReadTimeout(Statement statement, ConsistencyLevel cl, int requiredResponses, int receivedResponses, boolean dataRetrieved, int nbRetry) Defines whether to retry and at which consistency level on a read timeout.
RetryPolicy.RetryDecision	onRequestError(Statement statement, ConsistencyLevel cl, DriverException e, int nbRetry) Defines whether to retry and at which consistency level on an unexpected error.
RetryPolicy.RetryDecision	onUnavailable(Statement statement, ConsistencyLevel cl, int requiredReplica, int aliveReplica, int nbRetry) Defines whether to retry and at which consistency level on an unavailable exception.
RetryPolicy.RetryDecision	onWriteTimeout(Statement statement, ConsistencyLevel cl, WriteType writeType, int requiredAcks, int receivedAcks, int nbRetry) Defines whether to retry and at which consistency level on a write timeout.

Methods inherited from class java.lang.Object

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

Constructor Detail

IdempotenceAwareRetryPolicy

public IdempotenceAwareRetryPolicy(RetryPolicy childPolicy)

Creates a new instance.

Parameters:

childPolicy - the policy to wrap.

Method Detail

onReadTimeout

public RetryPolicy.RetryDecision onReadTimeout(Statement statement,
                                               ConsistencyLevel cl,
                                               int requiredResponses,
                                               int receivedResponses,
                                               boolean dataRetrieved,
                                               int nbRetry)

Description copied from interface: RetryPolicy

Defines whether to retry and at which consistency level on a read timeout.

Note that this method may be called even if requiredResponses >= receivedResponses if dataPresent is false (see ReadTimeoutException.wasDataRetrieved()).

Specified by:

onReadTimeout in interface RetryPolicy

Parameters:

statement - the original query that timed out.

cl - the requested consistency level of the read that timed out. Note that this can never be a serial consistency level.

requiredResponses - the number of responses that were required to achieve the requested consistency level.

receivedResponses - the number of responses that had been received by the time the timeout exception was raised.

dataRetrieved - whether actual data (by opposition to data checksum) was present in the received responses.

nbRetry - the number of retry already performed for this operation.

Returns:

the retry decision. If RetryDecision.RETHROW is returned, a ReadTimeoutException will be thrown for the operation.

onWriteTimeout

public RetryPolicy.RetryDecision onWriteTimeout(Statement statement,
                                                ConsistencyLevel cl,
                                                WriteType writeType,
                                                int requiredAcks,
                                                int receivedAcks,
                                                int nbRetry)

Description copied from interface: RetryPolicy

Defines whether to retry and at which consistency level on a write timeout.

Specified by:

onWriteTimeout in interface RetryPolicy

Parameters:

statement - the original query that timed out.

cl - the requested consistency level of the write that timed out. If the timeout occurred at the "paxos" phase of a Lightweight transaction, then cl will actually be the requested serial consistency level. Beware that serial consistency levels should never be passed to a RetryDecision as this would invariably trigger an InvalidQueryException. Also, when cl is serial, then writeType is always CAS.

writeType - the type of the write that timed out.

requiredAcks - the number of acknowledgments that were required to achieve the requested consistency level.

receivedAcks - the number of acknowledgments that had been received by the time the timeout exception was raised.

nbRetry - the number of retry already performed for this operation.

Returns:

the retry decision. If RetryDecision.RETHROW is returned, a WriteTimeoutException will be thrown for the operation.

onUnavailable

public RetryPolicy.RetryDecision onUnavailable(Statement statement,
                                               ConsistencyLevel cl,
                                               int requiredReplica,
                                               int aliveReplica,
                                               int nbRetry)

Description copied from interface: RetryPolicy

Defines whether to retry and at which consistency level on an unavailable exception.

Specified by:

onUnavailable in interface RetryPolicy

Parameters:

statement - the original query for which the consistency level cannot be achieved.

cl - the requested consistency level for the operation. If the operation failed at the "paxos" phase of a Lightweight transaction, then cl will actually be the requested serial consistency level. Beware that serial consistency levels should never be passed to a RetryDecision as this would invariably trigger an InvalidQueryException.

requiredReplica - the number of replica that should have been (known) alive for the operation to be attempted.

aliveReplica - the number of replica that were know to be alive by the coordinator of the operation.

nbRetry - the number of retry already performed for this operation.

Returns:

the retry decision. If RetryDecision.RETHROW is returned, an UnavailableException will be thrown for the operation.

onRequestError

public RetryPolicy.RetryDecision onRequestError(Statement statement,
                                                ConsistencyLevel cl,
                                                DriverException e,
                                                int nbRetry)

Description copied from interface: RetryPolicy

Defines whether to retry and at which consistency level on an unexpected error.

This method might be invoked in the following situations:

1. On a client timeout, while waiting for the server response (see SocketOptions.getReadTimeoutMillis());
2. On a connection error (socket closed, etc.);
3. When the contacted host replies with an error, such as OVERLOADED, IS_BOOTSTRAPPING, SERVER_ERROR, etc.

Note that when this method is invoked, the driver cannot guarantee that the mutation has been effectively applied server-side; a retry should only be attempted if the request is known to be idempotent.

Specified by:

onRequestError in interface RetryPolicy

Parameters:

statement - the original query that failed.

cl - the requested consistency level for the operation. Note that this is not necessarily the achieved consistency level (if any), and it is never a serial one.

e - the exception that caused this request to fail.

nbRetry - the number of retries already performed for this operation.

Returns:

the retry decision. If RetryDecision.RETHROW is returned, the DriverException passed to this method will be thrown for the operation.

init

public void init(Cluster cluster)

Description copied from interface: RetryPolicy

Gets invoked at cluster startup.

Specified by:

init in interface RetryPolicy

Parameters:

cluster - the cluster that this policy is associated with.

close

public void close()

Description copied from interface: RetryPolicy

Gets invoked at cluster shutdown.

This gives the policy the opportunity to perform some cleanup, for instance stop threads that it might have started.

Specified by:

close in interface RetryPolicy

isIdempotent

protected boolean isIdempotent(Statement statement)

Determines whether the given statement is idempotent or not.

The current implementation inspects the statement's idempotent flag; if this flag is not set, then it inspects QueryOptions.getDefaultIdempotence().

Subclasses may override if they have better knowledge of the statement being executed.

Parameters:

statement - The statement to execute.

Returns:

true if the given statement is idempotent, false otherwise