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https://issues.apache.org/jira/browse/IGNITE-6252?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16426566#comment-16426566
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Yashasvi Kotamraju commented on IGNITE-6252:
--------------------------------------------
*In CassandraSessionImpl.java*
*In method*
*@Override public <R, V> R execute(BatchExecutionAssistant<R, V> assistant,
Iterable<? extends V> data)*
*.................*
*ResultSet resSet = futureResult.getValue().getUninterruptibly();*
*Row row = resSet != null && resSet.iterator().hasNext() ?
resSet.iterator().next() : null;*
*if (row != null)*
*assistant.process(row, futureResult.getKey());*
*...................*
If prepared statements are Insert/Update/Delete then no result will be returned
according to Cassandra docs. Hence{color:#FF0000}
{color}*resSet.iterator().hasNext()* will always return false and so *row* will
always be null. Hence its not added to *assistant.process* so
*assistant.processedCount()* will always be 0. and never be equal to
*datasize*. We end up retrying eventhough it was inserted/deleted/updated and
there were no Exceptions, and try CQL_EXECUTION_ATTEMPTS_COUNT attempts trying
again and again and finally throw Exception :
*"Failed to process " + (dataSize - assistant.processedCount()) +*
*" of " + dataSize + " elements, during " + assistant.operationName() +*
*" operation with Cassandra"*
Hence the code fix using the condition : assistant.processedCount() == dataSize
will not work if prepared statement is not a select statement.
We can put a boolean flag *retry* which is set to false initially in every
attempt. If at any point the execution flow enters Exception code block then we
can set *retry* as true. Then instead of condition :
*if (tblAbsenceEx == null && hostsAvailEx == null && prepStatEx == null)*
we can use:
*if(!retry)*
as a condition on whether to return the processed data or retry.
In addition to this we need to maintain separate HashSet of keyvalues of
ResultSetFuture where
*resSet !=null && (* *resSet.iterator().hasNext()* == *false)* Which is the
case for Insert/Upadate/Delete preparedstatements.
Then while re attempting in addition to !assistant.alreadyProcessed(seqNum)
check we also check if the HashSet does not contains the seqNum.
> Cassandra Cache Store Session does not retry if prepare statement failed
> ------------------------------------------------------------------------
>
> Key: IGNITE-6252
> URL: https://issues.apache.org/jira/browse/IGNITE-6252
> Project: Ignite
> Issue Type: Bug
> Components: cassandra
> Affects Versions: 2.0, 2.1
> Reporter: Sunny Chan
> Assignee: Igor Rudyak
> Priority: Major
> Fix For: 2.5
>
>
> During our testing, we have found that certain warning about prepared
> statement:
> 2017-08-31 11:27:19.479
> org.apache.ignite.cache.store.cassandra.CassandraCacheStore
> flusher-0-#265%xxxx% WARN CassandraCacheStore - Prepared statement cluster
> error detected, refreshing Cassandra session
> com.datastax.driver.core.exceptions.InvalidQueryException: Tried to execute
> unknown prepared query : 0xc7647611fd755386ef63478ee7de577b. You may have
> used a PreparedStatement that was created with another Cluster instance.
> We notice that after this warning occurs some of the data didn't persist
> properly in cassandra cache. After further examining the Ignite's
> CassandraSessionImpl code in method
> execute(BatchExecutionAssistance,Iterable), we found that at around [line
> 283|https://github.com/apache/ignite/blob/86bd544a557663bce497134f7826be6b24d53330/modules/cassandra/store/src/main/java/org/apache/ignite/cache/store/cassandra/session/CassandraSessionImpl.java#L283],
> if the prepare statement fails in the asnyc call, it will not retry the
> operation as the error is stored in [line
> 269|https://github.com/apache/ignite/blob/86bd544a557663bce497134f7826be6b24d53330/modules/cassandra/store/src/main/java/org/apache/ignite/cache/store/cassandra/session/CassandraSessionImpl.java#L269]
> and cleared in [line
> 277|https://github.com/apache/ignite/blob/86bd544a557663bce497134f7826be6b24d53330/modules/cassandra/store/src/main/java/org/apache/ignite/cache/store/cassandra/session/CassandraSessionImpl.java#L277]
> but it was not checked again after going through the [ResultSetFuture
> |https://github.com/apache/ignite/blob/86bd544a557663bce497134f7826be6b24d53330/modules/cassandra/store/src/main/java/org/apache/ignite/cache/store/cassandra/session/CassandraSessionImpl.java#L307].
> I believe in line 307 you should check for error != null such that any
> failure will be retry.
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