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From HAITHEM JARRAYA <a-hjarr...@expedia.com>
Subject Question regarding java DowngradingConsistencyRetryPolicy
Date Tue, 04 Mar 2014 18:21:25 GMT
Hi All,

I might be missing something and I would like some clarification on this. We are using the
java driver with the Downgrading Retry policy, we see in our logs that are only the reads
are retried.

In the code and the docs, it says that the write method will retry a maximum of one retry,
when the WriteType is UNLOGGED_BATCH or BATCH_LOG.
My question is, when a write is considered as SIMPLE?

Thanks,

Haithem

    /**
     * Defines whether to retry and at which consistency level on a write timeout.
     * <p>
     * This method triggers a maximum of one retry. If {@code writeType ==
     * WriteType.BATCH_LOG}, the write is retried with the initial
     * consistency level. If {@code writeType == WriteType.UNLOGGED_BATCH}
     * and at least one replica acknowledged, 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 {@code receivedAcks > 0}). For other {@code writeType},
     * if we know the write has been persisted on at least one replica, we
     * ignore the exception. Otherwise, an exception is thrown.
     *
     * @param statement the original query that timed out.
     * @param cl the original consistency level of the write that timed out.
     * @param writeType the type of the write that timed out.
     * @param requiredAcks the number of acknowledgments that were required to
     * achieve the requested consistency level.
     * @param receivedAcks the number of acknowledgments that had been received
     * by the time the timeout exception was raised.
     * @param nbRetry the number of retry already performed for this operation.
     * @return a RetryDecision as defined above.
     */
    @Override
    public RetryDecision onWriteTimeout(Statement statement, ConsistencyLevel cl, WriteType
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 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);
        }
        // We want to rethrow on COUNTER and CAS, because in those case "we don't know" and
don't want to guess
        return RetryDecision.rethrow();
    }



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