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

[Tom - Droplet]

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






---------------------------------------------------------------------------------------
The information contained in this email and its attachments is confidential and may be the subject of legal, professional or other privilege. It is intended only for the named addressees and may not be disclosed to anyone else without consent from PolkaSpots Limited. If you are not the named addressee you must not use, disclose, distribute, copy, print or rely on the contents of this email and should destroy it immediately. Whilst PolkaSpots Limited takes care to protect its systems from electronic virus attack or other harmful event, the firm gives no warranty that this email message (including any attachments to it) is free of any virus or other harmful matter and accepts no responsibility for any loss or damage resulting from the recipient receiving, opening or using it. If you need any further information, please contact the originator of this message on +44 (0) 20 7183 1471.

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
---------------------------------------------------------------------------------------

_______________________________________________  
Chat mailing list  
Chat at lists.lrug.org  
http://lists.lrug.org/listinfo.cgi/chat-lrug.org  
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.lrug.org/pipermail/chat-lrug.org/attachments/20140321/f7952565/attachment-0003.html>