[rabbitmq-discuss] Claim on new ocamlmq broker...

mfp mfp at acm.org
Tue Jun 15 00:01:38 BST 2010

Alexis Richardson-5 wrote:
> On Mon, Jun 14, 2010 at 7:51 PM, Jason J. W. Williams
> <jasonjwwilliams at gmail.com> wrote:
>> This new OCAML STOMP broker makes this claim about Rabbit on it's page:
>> "RabbitMQ did not guarantee that persistent messages had been saved to
>> disk before sending the message receipt, which could lead to data
>> loss"
>> http://eigenclass.org/R2/writings/ocamlmq-release
>> Anyone else seen this behavior...I surely haven't. Messages disappear
>> in a cluster due to the way queues are handled...but I've never seen
>> this in a single instance.
> Yes, it's bs.

Does that mean that these comments by Matthew Sackman (who AFAIK works for
LShift and is a RabbitMQ developer) no longer apply?


> When you publish a message with delivery mode 2 you are *not* _guaranteed_
> that it hits disk. Publishing is an async operation and you get no
> confirmation that it goes to disk. The new persister does very aggressive
> caching in order to avoid doing lots of tiny and expensive writes. As
> such,
> there will frequently be times where if you restart the broker, you will
> lose
> several (maybe hundreds) of messages. 

Note that I'm referring to what happens in case of a hard RabbitMQ/system
crash. The behavior described by Matthew Sackman is consistent with what I
observed in the tests I did before writing ocamlmq: RabbitMQ accepting
persistent messages at fairly high rates, with quickly growing memory usage
no disk activity.


Mauricio Fernandez

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