[openstack-dev] [Zaqar] Zaqar and SQS Properties of Distributed Queues

Steve Lewis steve.lewis at RACKSPACE.COM
Thu Sep 18 15:42:00 UTC 2014


On September 18, 2014 7:45 AM, Flavio Percoco wrote:

> On 09/18/2014 04:09 PM, Gordon Sim wrote:
>
>> However, as far as consuming messages is concerned, it can
>> guarantee once-and-only-once and/or at-least-once delivery depending on
>> the message pattern used to consume messages. Using pop or claims
>> guarantees the former whereas streaming messages out of Zaqar guarantees
>> the later.
>>
>> From what I can see, pop provides unreliable delivery (i.e. its similar
>> to no-ack). If the delete call using pop fails while sending back the
>> response, the messages are removed but didn't get to the client.
> 
> Correct, pop works like no-ack. If you want to have pop+ack, it is
> possible to claim just 1 message and then delete it.

Having some experience using SQS I would expect that there would be a mode
something like what SQS provides where a message gets picked up by one 
consumer (let's say by short-polling) and is hidden for a timeout duration from 
other consumers, so that the consumer has time to ack. Is that how you are 
using the term 'claim' in this case?



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