/// <summary>
/// Defines whether to retry and at which consistency level on a write timeout.
/// <p> This method triggers a maximum of one retry. If <c>writeType ==
/// WriteType.BATCH_LOG</c>, the write is retried with the initial consistency
/// level. If <c>writeType == WriteType.UNLOGGED_BATCH</c> and at least one
/// replica acknowleged, the write is retried with a lower consistency level
/// (with unlogged batch, a write timeout can <b>always</b> mean that part of the
/// batch haven't been persisted at' all, even if <c>receivedAcks > 0</c>).
/// For other <c>writeType</c>, if we know the write has been persisted on
/// at least one replica, we ignore the exception. Otherwise, an exception is
/// thrown.</p>
/// </summary>
/// <param name="query"> the original query that timeouted. </param>
/// <param name="cl"> the original consistency level of the write that timeouted.
/// </param>
/// <param name="writeType"> the type of the write that timeouted. </param>
/// <param name="requiredAcks"> the number of acknowledgments that were required
/// to achieve the requested consistency level. </param>
/// <param name="receivedAcks"> the number of acknowledgments that had been
/// received by the time the timeout exception was raised. </param>
/// <param name="nbRetry"> the number of retry already performed for this
/// operation. </param>
///
/// <returns>a RetryDecision as defined above.</returns>
public RetryDecision OnWriteTimeout(IStatement query, ConsistencyLevel cl, string writeType, int requiredAcks, int receivedAcks, int nbRetry)
{
if (nbRetry != 0)
{
return(RetryDecision.Rethrow());
}
switch (writeType)
{
case "SIMPLE":
case "BATCH":
// Since we provide atomicity there is no point in retrying
return(RetryDecision.Ignore());
case "COUNTER":
// We should not retry counters, period!
return(RetryDecision.Ignore());
case "UNLOGGED_BATCH":
// Since only part of the batch could have been persisted,
// retry with whatever consistency should allow to persist all
return(MaxLikelyToWorkCl(receivedAcks));
case "BATCH_LOG":
return(RetryDecision.Retry(cl));
}
return(RetryDecision.Rethrow());
}
/// <summary>
/// Gets the retry decision based on the exception from Cassandra
/// </summary>
public RetryDecision GetRetryDecision(Exception ex)
{
RetryDecision decision = RetryDecision.Rethrow();
if (ex is SocketException)
{
decision = RetryDecision.Retry(null);
}
else if (ex is OverloadedException || ex is IsBootstrappingException || ex is TruncateException)
{
decision = RetryDecision.Retry(null);
}
else if (ex is ReadTimeoutException)
{
var e = ex as ReadTimeoutException;
decision = _retryPolicy.OnReadTimeout(_statement, e.ConsistencyLevel, e.RequiredAcknowledgements, e.ReceivedAcknowledgements, e.WasDataRetrieved, _retryCount);
}
else if (ex is WriteTimeoutException)
{
var e = ex as WriteTimeoutException;
decision = _retryPolicy.OnWriteTimeout(_statement, e.ConsistencyLevel, e.WriteType, e.RequiredAcknowledgements, e.ReceivedAcknowledgements, _retryCount);
}
else if (ex is UnavailableException)
{
var e = ex as UnavailableException;
decision = _retryPolicy.OnUnavailable(_statement, e.Consistency, e.RequiredReplicas, e.AliveReplicas, _retryCount);
}
return(decision);
}
/// <summary>
/// The default implementation triggers a retry on the next host in the query plan with the same consistency level,
/// regardless of the statement's idempotence, for historical reasons.
/// </summary>
public RetryDecision OnRequestError(IStatement statement, Configuration config, Exception ex, int nbRetry)
{
if (ex is OperationTimedOutException && !config.QueryOptions.RetryOnTimeout)
{
return(RetryDecision.Rethrow());
}
return(RetryDecision.Retry(null, false));
}
/// <summary>
/// Defines whether to retry and at which consistency level on a write timeout.
/// <p> This method triggers a maximum of one retry, and only in the case of a
/// <c>WriteType.BATCH_LOG</c> write. The reasoning for the retry in that
/// case is that write to the distributed batch log is tried by the coordinator
/// of the write against a small subset of all the node alive in the local
/// datacenter. Hence, a timeout usually means that none of the nodes in that
/// subset were alive but the coordinator hasn't' detected them as dead. By the
/// time we get the timeout the dead nodes will likely have been detected as dead
/// and the retry has thus a high change of success.</p>
/// </summary>
/// <param name="query"> the original query that timeouted. </param>
/// <param name="cl"> the original consistency level of the write that timeouted.
/// </param>
/// <param name="writeType"> the type of the write that timeouted. </param>
/// <param name="requiredAcks"> the number of acknowledgments that were required
/// to achieve the requested consistency level. </param>
/// <param name="receivedAcks"> the number of acknowledgments that had been
/// received by the time the timeout exception was raised. </param>
/// <param name="nbRetry"> the number of retry already performed for this
/// operation. </param>
///
/// <returns><c>RetryDecision.retry(cl)</c> if no retry attempt has yet
/// been tried and <c>writeType == WriteType.BATCH_LOG</c>,
/// <c>RetryDecision.rethrow()</c> otherwise.</returns>
public RetryDecision OnWriteTimeout(IStatement query, ConsistencyLevel cl, string writeType, int requiredAcks, int receivedAcks,
int nbRetry)
{
if (nbRetry != 0)
{
return(RetryDecision.Rethrow());
}
// If the batch log write failed, retry the operation as this might just be we were unlucky at picking candidtes
return(writeType == "BATCH_LOG" ? RetryDecision.Retry(cl) : RetryDecision.Rethrow());
}
/// <inheritdoc />
public RetryDecision OnRequestError(IStatement stmt, Configuration config, Exception ex, int nbRetry)
{
if (stmt != null && stmt.IsIdempotent == true)
{
if (_extendedChildPolicy != null)
{
return(_extendedChildPolicy.OnRequestError(stmt, config, ex, nbRetry));
}
return(RetryDecision.Retry(null, false));
}
return(RetryDecision.Rethrow());
}
/// <summary>
/// Defines whether to retry and at which consistency level on a read timeout.
/// <p> This method triggers a maximum of one retry, and only if enough replica
/// had responded to the read request but data was not retrieved amongst those.
/// Indeed, that case usually means that enough replica are alive to satisfy the
/// consistency but the coordinator picked a dead one for data retrieval, not
/// having detected that replica as dead yet. The reasoning for retrying then is
/// that by the time we get the timeout the dead replica will likely have been
/// detected as dead and the retry has a high change of success.</p>
/// </summary>
/// <param name="query"> the original query that timed out. </param>
/// <param name="cl"> the original consistency level of the read that timed out.
/// </param>
/// <param name="requiredResponses"> the number of responses that were required
/// to achieve the requested consistency level. </param>
/// <param name="receivedResponses"> the number of responses that had been
/// received by the time the timeout exception was raised. </param>
/// <param name="dataRetrieved"> whether actual data (by opposition to data
/// checksum) was present in the received responses. </param>
/// <param name="nbRetry"> the number of retry already performed for this
/// operation. </param>
///
/// <returns><c>RetryDecision.Retry(cl)</c> if no retry attempt has yet
/// been tried and <c>receivedResponses >= requiredResponses &&
/// !dataRetrieved</c>, <c>RetryDecision.Rethrow()</c>
/// otherwise.</returns>
public RetryDecision OnReadTimeout(IStatement query, ConsistencyLevel cl, int requiredResponses, int receivedResponses,
bool dataRetrieved, int nbRetry)
{
if (nbRetry != 0)
{
return(RetryDecision.Rethrow());
}
return(receivedResponses >= requiredResponses && !dataRetrieved
? RetryDecision.Retry(cl)
: RetryDecision.Rethrow());
}
private static RetryDecision MaxLikelyToWorkCl(int knownOk)
{
if (knownOk >= 3)
{
return(RetryDecision.Retry(ConsistencyLevel.Three));
}
if (knownOk >= 2)
{
return(RetryDecision.Retry(ConsistencyLevel.Two));
}
if (knownOk >= 1)
{
return(RetryDecision.Retry(ConsistencyLevel.One));
}
return(RetryDecision.Rethrow());
}
/// <summary>
/// Defines whether to retry and at which consistency level on a read timeout.
/// <p> This method triggers a maximum of one retry. If less replica responsed
/// than required by the consistency level (but at least one replica did
/// respond), the operation is retried at a lower consistency level. If enough
/// replica responded but data was not retrieve, the operation is retried with
/// the initial consistency level. Otherwise, an exception is thrown.</p>
/// </summary>
/// <param name="query"> the original query that timeouted. </param>
/// <param name="cl"> the original consistency level of the read that timeouted.
/// </param>
/// <param name="requiredResponses"> the number of responses that were required
/// to achieve the requested consistency level. </param>
/// <param name="receivedResponses"> the number of responses that had been
/// received by the time the timeout exception was raised. </param>
/// <param name="dataRetrieved"> whether actual data (by opposition to data
/// checksum) was present in the received responses. </param>
/// <param name="nbRetry"> the number of retry already performed for this
/// operation. </param>
///
/// <returns>a RetryDecision as defined above.</returns>
public RetryDecision OnReadTimeout(IStatement query, ConsistencyLevel cl, int requiredResponses, int receivedResponses, bool dataRetrieved,
int nbRetry)
{
if (nbRetry != 0)
{
return(RetryDecision.Rethrow());
}
if (receivedResponses < requiredResponses)
{
// Tries the biggest CL that is expected to work
return(MaxLikelyToWorkCl(receivedResponses));
}
return(!dataRetrieved?RetryDecision.Retry(cl) : RetryDecision.Rethrow());
}
static RetryDecision GetRetryDecision(Query query, QueryValidationException exc, IRetryPolicy policy, int queryRetries)
{
if (exc is OverloadedException)
{
return(RetryDecision.Retry(null));
}
else if (exc is IsBootstrappingException)
{
return(RetryDecision.Retry(null));
}
else if (exc is TruncateException)
{
return(RetryDecision.Retry(null));
}
else if (exc is ReadTimeoutException)
{
var e = exc as ReadTimeoutException;
return(policy.OnReadTimeout(query, e.ConsistencyLevel, e.RequiredAcknowledgements, e.ReceivedAcknowledgements, e.WasDataRetrieved, queryRetries));
}
else if (exc is WriteTimeoutException)
{
var e = exc as WriteTimeoutException;
return(policy.OnWriteTimeout(query, e.ConsistencyLevel, e.WriteType, e.RequiredAcknowledgements, e.ReceivedAcknowledgements, queryRetries));
}
else if (exc is UnavailableException)
{
var e = exc as UnavailableException;
return(policy.OnUnavailable(query, e.Consistency, e.RequiredReplicas, e.AliveReplicas, queryRetries));
}
else if (exc is AlreadyExistsException)
{
return(RetryDecision.Rethrow());
}
else if (exc is InvalidConfigurationInQueryException)
{
return(RetryDecision.Rethrow());
}
else if (exc is PreparedQueryNotFoundException)
{
return(RetryDecision.Rethrow());
}
else if (exc is ProtocolErrorException)
{
return(RetryDecision.Rethrow());
}
else if (exc is InvalidQueryException)
{
return(RetryDecision.Rethrow());
}
else if (exc is UnauthorizedException)
{
return(RetryDecision.Rethrow());
}
else if (exc is SyntaxError)
{
return(RetryDecision.Rethrow());
}
else if (exc is ServerErrorException)
{
return(null);
}
else
{
return(null);
}
}