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Docker Info Example Plugin

Description

Let's say we want to use check_http_json.py to read from Docker's /info HTTP API endpoint with the following parameters:

Connection information
  • Host = 127.0.0.1:4243
  • Path = /info
Rules for "aliveness"
  • Verify that the key Containers exists in the outputted JSON
  • Verify that the key IPv4Forwarding has a value of 1
  • Verify that the key Debug has a value less than or equal to 2
  • Verify that the key Images has a value greater than or equal to 1
  • If any of these criteria are not met, report a WARNING to Nagios
Gather Metrics
  • Report value of the key Containers with a MinValue of 0 and a MaxValue of 1000 as performance data
  • Report value of the key Images as performance data
  • Report value of the key NEventsListener as performance data
  • Report value of the key NFd as performance data
  • Report value of the key NGoroutines as performance data
  • Report value of the key SwapLimit as performance data

Service Definition

localhost.cfg

define service {
        use                             local-service
        host_name                       localhost
        service_description             Docker info status checker
        check_command                   check_docker
        }

Command Definition with Arguments

commands.cfg

define command{
        command_name    check_docker
        command_line    /usr/bin/python /usr/local/nagios/libexec/plugins/check_http_json.py -H 127.0.0.1:4243 -p info -e Containers -q IPv4Forwarding,1 -w Debug,2:2 -c Images,1:1 -m Containers,0:250,0:500,0,1000 Images NEventsListener NFd NGoroutines SwapLimit
        }

Sample Output

OK: Status OK.|'Containers'=1;0;1000 'Images'=11;0;0 'NEventsListener'=3;0;0 'NFd'=10;0;0 'NGoroutines'=14;0;0 'SwapLimit'=1;0;0

Docker Container Monitor Example Plugin

check_http_json.py is generic enough to read and evaluate rules on any HTTP endpoint that returns JSON. In this example we'll get the status of a specific container using it's ID which camn be found by using the list containers endpoint (curl http://127.0.0.1:4243/containers/json?all=1).

Connection information
  • Host = 127.0.0.1:4243
  • Path = /containers/2356e8ccb3de8308ccb16cf8f5d157bc85ded5c3d8327b0dfb11818222b6f615/json
Rules for "aliveness"
  • Verify that the key ID exists and is equal to the value 2356e8ccb3de8308ccb16cf8f5d157bc85ded5c3d8327b0dfb11818222b6f615
  • Verify that the key State.Running has a value of True

Service Definition

localhost.cfg

define service {
        use                             local-service
        host_name                       localhost
        service_description             Docker container liveness check
        check_command                   check_my_container
        }

Command Definition with Arguments

commands.cfg

define command{
        command_name    check_my_container
        command_line    /usr/bin/python /usr/local/nagios/libexec/plugins/check_http_json.py -H 127.0.0.1:4243 -p /containers/2356e8ccb3de8308ccb16cf8f5d157bc85ded5c3d8327b0dfb11818222b6f615/json -q ID,2356e8ccb3de8308ccb16cf8f5d157bc85ded5c3d8327b0dfb11818222b6f615 State.Running,True
        }

Sample Output

WARNING: Status check failed, reason: Value True for key State.Running did not match.

The plugin threw a warning because the Container ID I used on my system has the following State object:

 u'State': {...
            u'Running': False,
            ...

If I change the command to have the parameter -q parameter State.Running,False, the output becomes:

OK: Status OK.