[LRUG] AMQP threads. Where did my messages go?

Fri Mar 21 05:47:39 PDT 2014

Hi Jim

Thanks for the email. I have two coffees on my desk right now, I can send
one over..

We were actually using bunny until last night but swapped over to AMQP gem
as a test. There's a bunny issue that's just been closed that sort of
addressed our problem (
https://groups.google.com/forum/#!topic/ruby-amqp/_ZShRP6FRXI). Wanted to
eliminate that part despite running a later version.

It's actually the latter we seem to be struggling with. They seem to
disappear between Rabbit and Node. Thanks for the info though, good to
learn new stuff.

S

Simon Morley
Big Chief | PolkaSpots Supafly Wi-Fi

simon at PolkaSpots.com
020 7183 1471

Follow our updates on twitter: twitter.com/polkaspots
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On 21 March 2014 12:30, Jim Myhrberg <contact at jimeh.me> wrote:

> Hey Simon,
>
> My AMQP skills have been gathering dust for a couple of years at this
> point, but I'll see if I can help.
>
> First, maybe I haven't had enough caffeine today, so would mind clarifying
> if the issue is that the notification messages don't get pushed from the
> Ruby worker, or they do show up fine in RabbitMQ and then disappear between
> RabbitMQ and the Node.js worker?
>
> If it's the former, one thing to keep in mind when using the amqp gem, is
> that calling #push doesn't mean the message has been pushed, it means it
> will be pushed at some point in the future when the event loop gets to it.
> Typically if I recall, anything/everything pushed within processing one
> AMQP message, get's all gets pushed at once after the ACK for the initial
> message being processed is sent back to RabbitMQ. Another thing to keep in
> mind is that killing the connection/process/whatever even after finishing
> processing the initial message might cut off your messages being pushed.
>
> The async nature of the amqp gem can cause some weird timing issues. Hence
> when I last used AMQP we ended up replacing the amqp gem where async wasn't
> specifically required with the synchronous bunny gem instead to make things
> simpler.
>
>
>
>
>
> --jimeh
>
>
> On Fri, Mar 21, 2014 at 12:10 PM, Simon Morley <simon at polkaspots.com>wrote:
>
>> Hi Tom, Steve
>>
>> Thanks for your emails.
>>
>> We have ack on for everything right now. We can see the 'parent' job
>> being queued, the follow up jobs don't seem to be queued - I'll confirm
>> this shortly.
>>
>> I have no unacked messages either right now.
>>
>> I'd thought the consumer might be dying which is why we ran the child job
>> in a loop. No problems encountered.
>>
>> Just can't see why they work independently, just not as one.
>>
>> S
>>
>> Simon Morley
>> Big Chief | PolkaSpots Supafly Wi-Fi
>>
>> simon at PolkaSpots.com
>> 020 7183 1471
>>
>> Follow our updates on twitter: twitter.com/polkaspots
>> Try Wi-Fi As A Service (WaaS) here: http://bit.ly/15UymJ8
>>
>>
>>
>>
>>
>>
>>
>>
>> On 21 March 2014 11:59, Tom - Droplet <tom at dropletpay.com> wrote:
>>
>>> Hi Simon,
>>>
>>> What are your publisher confirm settings and consumer ack settings?
>>> Could it be that the consumer dies during processing the job but you have
>>> subscribed to the queue without requiring acks, so the message is
>>> essentially lost?
>>>
>>> The RabbitMQ management page can be pretty useful for debugging this
>>> kind of stuff sometimes, you can check that messages are getting put in the
>>> queue as you expect and pull them out to see the message.
>>>
>>> --
>>> Tom Livesey
>>> Lead engineer - Droplet
>>> dropletpay.com
>>>
>>>
>>> On 21 March 2014 at 11:48:05, Simon Morley (simon at polkaspots.com) wrote:
>>>
>>> Morning All
>>>
>>> Having asked SO, I remembered we were supposed to be encouraging more
>>> questions here! I hope you can help (sorry this is a long message).
>>>
>>> Relatively new to the world of RabbitMQ, I'm getting stuck debugging the
>>> problem of missing messages. All was / is fine in my dev. environment, the
>>> problems arise when we start chucking thousand of messages at things.
>>>
>>> I've narrowed the problem down to messages that are sent from within
>>> another job. For example, we have a job that moves a customer's
>>> subscription when they sign up. We publish this to our rabbit servers using
>>> the AMQP gem and EM using something like this:
>>>
>>> https://gist.github.com/simonmorley/9684010
>>>
>>> def queue_process_subscription
>>>    user. process_subscription
>>> end
>>>
>>> def process_subscription
>>>   hammer_time
>>>   MESSAGE_QUEUE.push(json_message, 'ps.routing.key')
>>> end
>>>
>>> After the job's been completed, we use MESSAGE_QUEUE to push a message
>>> to our notification servers (which run NodeJS, node-amqp and SocketIO).
>>>
>>> On my lonely laptop, the jobs process perfectly, the notification are
>>> sent and my SocketIO client receives them. Happy days.
>>>
>>> On my production servers, the job is queued in RabbitMq, processed
>>> perfectly and the notification is published apparently. The problem is, it
>>> doesn't appear to be received by the node amqp consumer 100% of the time.
>>> Maybe 1 in 10 get delivered (and sometimes they don't look like the full
>>> message). The rest just vanish.. It gets worse as we load the servers up.
>>>
>>> I thought it was the AMQP on the Node servers but I created a loop to
>>> run MESSAGE_QUEUE 10,000 times and they were all consumed..
>>>
>>> So, I'm assuming the problem is that we're sending a message from within
>>> another thread. At least, that's what I think it is. My knowledge of such
>>> things has now come to an end...
>>>
>>> We've now replaced the last notification with Redis publish which works
>>> a treat. But that's another cog to think about.
>>>
>>> Like I said, I'm new to this messaging / threading stuff,  and would
>>> appreciate it if someone can point me in the right direction, tell me what
>>> to read or suggestion something else to try. Or tell me to give up and go
>>> home.
>>>
>>> Cheers
>>>
>>> Simon
>>>
>>>
>>>
>>>  Simon Morley
>>> Big Chief | PolkaSpots Supafly Wi-Fi
>>>
>>> simon at PolkaSpots.com
>>> 020 7183 1471
>>> @polkaspots
>>>
>>>
>>>
>>>
>>>
>>>
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>

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PolkaSpots Limited is registered in the UK, number 05508105. Registered Office: 62 Britton Street (behind the bike sheds), Clerkenwell, London EC1M 5UY

Website: polkaspots.com
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Blog: polkaspots.com/blog
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