On Wed, Oct 6, 2010 at 10:56 AM, Elliot Murphy <[email protected]> wrote: > On Mon, Oct 4, 2010 at 10:35 PM, Robert Collins > <[email protected]> wrote: >> Rabbit isn't reliable - specifically by default it doesn't fsync >> before acknowledging, and it has no HA story to deal with server >> crashes/power failures. > > This caught my attention, and didn't quite jive with what I thought I > was told by the RabbitMQ devs, so I double checked (first rule of > talking to lifeless: always double-check, he is probably right!). So > the story is that RabbitMQ is perfectly durable if you mark the queue > as persistent and mark your message as persistent, which is very > simple to do. For crash recovery, if you are running in persistent > mode and the server is unplugged, you simply bring it back online and > no messages are lost, which is every bit as good as our current > postgres story. I don't think launchpad needs more than that, but just > in case there does appear to be an Active/Passive HA solution for > Rabbit described on their site. Here is the raw info from Matthias, > the lead dev for RabbitMQ: > > "by default it doesn't fsync before acknowledging" is about right. In > fact there is no acknowledging to publishers *at all*. > > But... just switch the AMQP channel into transactional mode and > publish persistent messages to durable queues, and you get the > guarantee that every published message will have been written to disk > by the time the tx.commit-ok arrives.
Yup - it supports it for sure but at a cost. We don't know how much the cost will hurt us yet. The important thing is that we need to choose message by message what requirements we have. > Needless to say that is quite expensive, which is why it is not the > default mode of operation. But there are many happy rabbit users who > running systems on that basis. And we have some protocol extensions in > the pipeline that improve performance significantly by providing > streaming publisher acks outside the context of transactions. > > As for HA... see http://www.rabbitmq.com/pacemaker.html Again, there > are quite a few rabbit users who use that or a similar setup. Thanks for referencing that; I was told by our U1 colleagues that the HA story was incomplete/lacking. That page clearly shows they have a more complete story, though I can't say that its at the level of maturity that (say) a queue built on cassandra would be. That said, I have a -great- deal of confidence in our server environment, I would defer building out HA on rabbit until we need it - the service itself is reputedly rocksolid, and the servers it runs on are very robust too. -Rob _______________________________________________ Mailing list: https://launchpad.net/~launchpad-dev Post to : [email protected] Unsubscribe : https://launchpad.net/~launchpad-dev More help : https://help.launchpad.net/ListHelp
