check_http_json

This is a plugin for Nagios that will parse JSON from an HTTP response. It is written in Ruby.

Usage

Usage: ./check_http_json.rb -u <URI> -e <element> -w <warn> -c <crit>
-h, --help                       Help info.
-v, --verbose                    Additional human output.
-u, --uri URI                    Target URI. Incompatible with -f.
-f, --file PATH                  Target file. Incompatible with -u.
-e, --element ELEMENT            Desired element (ex. foo=>bar=>ish is foo.bar.ish).
-E, --element_regex REGEX        Desired element expressed as regular expression.
-d, --delimiter CHARACTER        Element delimiter (default is period).
-w, --warn VALUE                 Warning threshold (integer).
-c, --crit VALUE                 Critical threshold (integer).
-r, --result STRING              Expected string result. No need for -w or -c.
-R, --result_regex REGEX         Expected string result expressed as regular expression. No need for -w or -c.
-W, --result_warn STRING         Warning if element is [string]. -C is required.
-C, --result_crit STRING         Critical if element is [string]. -W is required.
-t, --timeout SECONDS            Wait before HTTP timeout.

The --warn and --crit arguments conform to the Nagios threshold format guidelines.

If a simple result of either string or regular expression (-r or -R) is specified :

• A match is OK and anything else is CRIT.
• The warn / crit thresholds will be ignored.

If the warn and crit results (-W and -C) are specified :

• A match is WARN or CRIT and anything else is OK.
• The warn / crit thresholds will be ignored.

Note that (-r or -R) and (-W and -C) are mutually exclusive.

Note also that the response must be pure JSON. Bad things happen if this isn't the case.

Implementation

How you choose to implement the plugin is, of course, up to you. Here are some suggestions :

given string element, check string result

define command {
    command_name    check_http_json-string
    command_line    /etc/nagios3/plugins/check_http_json.rb -u 'http://$HOSTNAME$:$ARG1$/$ARG2$' -e '$ARG3$' -r '$ARG4$'
}
define service {
    service_description     elasticsearch-cluster-status
    check_command           check_http_json-string!9200!_cluster/health!status!green
}

wildly generic

define command {
    command_name    check_http_json
    command_line    /etc/nagios3/plugins/check_http_json.rb -u 'http://$HOSTNAME$:$ARG1$/$ARG2$' $ARG3$
}
define service {
    service_description     elasticsearch-resident-memory
    check_command           check_http_json!9280!_cluster/nodes/_local/stats!-E resident_in_bytes -w 1024000000 -c 1536000000
}

The script is licensed using the Apache License, Version 2.0.

Finally, I invite you to peruse the commit history for the list of contributors.

GitHub pull requests welcome ! Please send pull requests to the testing branch.