Monday, October 7, 2013

Nagios monitoring for Amazon SQS queue depth

I have found that a bunch of messages stacking up in my SQS queue's can be the first sign of something breaking. Several things can cause messages to stack up in the queue. I have seen malformed messages, slow servers and dead processes all cause this at different times. So to monitor the queue depth I wrote this Nagios check / plug-in. The check simply queries the SQS api and finds out the count of messages in each queue. Then it compares the count to the warning and critical levels.

This check is written in python and uses the boto library. It includes perfdata output so you can graph the number of messages in the queue. The the AWS API for SQS does wildcard matching of queue names so you can monitor a bunch of queues with one check if they have some sort of common prefix to the name. The way I use this is I have several individual checks using the complete explicit name of the queue and then a catchall using a wildcard set to a higher number that will catch any queues that have been added. Make sure you have a .boto file for the user that will be running this nagios check. It only requires read permissions.

Some queues may be more time sensitive than others. That is the case for my setup. For queues that are time sensitive I set the warning and critical counts to low values. Less time sensitive queues are set to higher count values. This screenshot is an example of that:


Here is the command definition I use for Naigos:

# 'check_sqs_depth' command definition
define command{
        command_name    check_sqs_depth
        command_line    /usr/lib/nagios/plugins/ --name '$ARG1$' --region '$ARG2$' --warn '$ARG3$' --crit '$ARG4$'

and here is the service definition I'm using

define service{
        use                                 generic-service   
        service_description          example_name SQS Queue
        contact_groups                admins,admins-page,sqs-alerts
        check_command             check_sqs_depth!example_name!us-east-1!150!300!


The code is available on my github nagios-checks repository here: and I have posted it as a gist below. My git repository will have the most up-to-date version

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