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

Simon Morley simon at polkaspots.com
Fri Mar 21 06:30:03 PDT 2014 

Ok. Back to the drawing board. I'll try that.

I'm assuming therefore there's no biggy running a job within a job, so to
speak..

Simon Morley
Big Chief | PolkaSpots Supafly Wi-Fi

simon at PolkaSpots.com
020 7183 1471

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On 21 March 2014 13:11, Jim Myhrberg <contact at jimeh.me> wrote:

> In that case I'd take your Ruby worker out of the equation, and stress
> test your notification queue and Node.js worker by having a custom script
> or something flood the notification queue with messages, upping the message
> rate until you're starting to see the Node.js worker misbehaving. In theory
> you should be able to do this even on your local dev machine, unless
> production and dev run different OSs and the issue stems from something OS
> specific that RabbitMQ or Node.js relies upon.
>
>
>
> --jimeh
>
>
> On Fri, Mar 21, 2014 at 12:47 PM, Simon Morley <simon at polkaspots.com>wrote:
>
>> 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
>> Try Wi-Fi As A Service (WaaS) here: http://bit.ly/15UymJ8
>>
>>
>>
>>
>>
>>
>>
>>
>> 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
WiFi Shop: shop.polkaspots.com
Blog: polkaspots.com/blog
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