AppStatus

AppStatus is a Rails engine which makes it easy to expose application status data in a way easily consumed by Nagios or other monitoring packages.

Installation

Gemfile

gem 'app_status'

config/routes.rb

Wire it up.

mount AppStatus::Engine, at: "/status"

This exposes the following URLs

• http://localhost:3000/status renders html or json according to Accept headers. Defaults to JSON.
• http://localhost:3000/status/index.json
• http://localhost:3000/status/index.html <-- fugly

config/initializers/app_status.rb

This is where you set up the checks which you want to be run when someone hits the URL above. Set up some calls which evaluate the health of your application and call add for each one.

AppStatus::CheckCollection.configure do |c|
  value = some_service_check
  c.add(:name => 'some_service', :status => :ok, :details => value)
end

The checks that you set up here are not run when you configure them. They're run whenever someone hits the check URL.

Status values (in ascending order of seriousness)

• :ok
• :warning
• :critical
• :unknown

These are set up to be compatible with Nagios.

Details doesn't have to be a string. It can be anything which is serializable as JSON.

Usage

$ curl -H 'Accept: application/json' http://localhost:3000/status

Output will look something like this:

{
  "status": "critical",
  "status_code": 2,
  "run_time_ms": 52,
  "finished": "2013-10-03T21:28:10Z",
  "checks": {
    "some_service": {
      "status": "ok",
      "status_code": 0,
      "details": "Looks good!"
    },
    "failing_service": {
      "status": "critical",
      "status_code": 2,
      "details": "Oh noes!"
    }
  }
}

The overall status will be the worst status which is actually observed in your individual checks.

Nagios Integration

bin/check_app_status.rb is a Nagios check script which can be used to monitor the output from app_status

$ bin/check_app_status.rb --help
Nagios check script for app_status. See https://github.com/alexdean/app_status
    -v, --verbose                    Output more information
    -V, --version                    Output version information
    -h, --help                       Display this screen
    -u, --url VAL                    Url to monitor
    -a, --auth VAL                   HTTP basic auth in the form 'user:password'
    -t, --timeout VAL                Timeout after waiting this long for a response.

The script's exit status is derived from the overall status returned by the server. Individual detail items will be grouped by status for display. (Unknowns are displayed together, then criticals, then warnings, then OKs.)

Sample output (using verbose mode)

$ bin/check_app_status.rb --url http://localhost:3000/status -v
2013-10-03T20:54:16-05:00  options: {:timeout=>10, :url=>"http://localhost:3000/status"}
2013-10-03T20:54:16-05:00  timeout: 10s
2013-10-03T20:54:16-05:00  response body: {"status":"warning","status_code":1,"run_time_ms":0,"finished":"2013-10-04T01:54:16Z","details":{"some_service":{"status":"ok","status_code":0,"details":"Looks good!"},"failing_service":{"status":"warning","status_code":1,"details":"Oh noes!"}}}

WARN: failing_service:'Oh noes!'
OK: some_service:'Looks good!'