[rabbitmq-discuss] RabbitMQ failover and message loss

[Jason J. W. Williams]

Great use case for an auto-replay option when dead nodes return. ;)

-J

On Fri, May 21, 2010 at 8:50 AM, Matthew Sackman <matthew at rabbitmq.com> wrote:
> On Fri, May 21, 2010 at 06:55:57PM +0530, Radha Krishnan D wrote:
>> I have 2 brokers clustered with each other.  They are load balanced by
>> having a HA proxy before them.
>
> Ok, that's not a usual setup. If you actually have the two rabbit nodes
> clustered together then you should have no need for the load balancer -
> all clients can connect to either node and still reach every resource in
> the broker.
>
>> Now both P1 and C1 get connected to B2 and the test continues till we
>> stop all three.
>>
>> Now, during the failover time we find message losses.
>>
>> Is it expected  or can we make sure that no message gets lost.
>
> That is expected. Queues are located on the node of the connection which
> created the queue. When the node goes down, you'll lose that queue. When
> your clients (re)connect to the broker and reach the other node, they
> are recreating the queues and other resources, but are creating fresh,
> empty queues at that point.
>
> If you need to be able to withstand node failures then currently your
> best bet is to use the Pacemaker Active/Passive guide at:
> http://www.rabbitmq.com/pacemaker.html
> You will need to publish all messages persistent to durable queues. You
> should not need the load balancer and pacemaker will correctly ensure
> that the two nodes are not both up at the same time.
>
>> Also, when will be  channel.setReturnListener  called ?
>
> Well, you set it yourself. The ReturnListener is invoked as soon as any
> Basic.Return method is read off the socket.
>
>> Will it be called when the message does not reach the queue from the
>> exchange or when the message does reach the consumer from the queue ?
>
> This is the difference between immediate and mandatory. Mandatory says
> "blow up if the msg doesn't make it to a queue". Immediate says "blow up
> if the msg doesn't make it through a queue to a consumer".
>
>> In the clustered mode, exchanges are global across rabbitmq nodes .. are
>> the queues also global ?
>
> They are visible globally within the cluster, but they are located in a
> node.
>
> Matthew
>
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