[rabbitmq-discuss] Transactions and duplicate
simon at rabbitmq.com
Thu Mar 27 17:42:32 GMT 2014
Using transactions does not prevent messages from being duplicated I'm
afraid. The transactions are quite thin, they are not ACID. See
Messages that are in flight can always be duplicated when the client or
On 26/03/14 15:12, lepolac wrote:
> When using transactions on the consumer side, I noticed duplicates when a
> node is failing.
> This occurs when the node the consumer is connected to fails, or if the
> master fails.
> It occurs both when catching the consumer cancellation exception and
> reconnecting directly, or using a simpler client and restarting it.
> I used a tx channel with basic.get and no autoack, I manually ack() and
> commit() every message.
> Whilst I can understand redelivery/dups when using asynchronous ways of
> consuming, I fail to see why it happens when using synchronous calls.
> I can reproduce this everytime, I always get one message redelivered, even
> if the commit() called return.
> I noticed that when throttling the consumer (let's say one message consumed
> every 100ms), I don't get dups.
> So, is the commit() call really synchronous ?
> Generally, what would be the best way to avoid duplicates ? I tried
> basicAck() without transactions and got the same results, I get dups.
> I'm using 3.2.4 and the java client.
> There's about 1ms latency between rabbit nodes and my client.
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