UnicornMetrics

Gather metrics from a Ruby application. Specifically targeted at Rack-based applications that use the Unicorn preforking webserver

Installation

Add this line to your application's Gemfile:

gem 'unicorn_metrics'

And then execute:

$ bundle

Or install it yourself as:

$ gem install unicorn_metrics

Usage

Counters

UnicornMetrics::Counter implements a convenient wrapper around an atomic counter. Register new counters in the application:

    UnicornMetrics.configure do |c|
      # Configure a new counter with the name 'test_counter'
      # Then access this counter UnicornMetrics.test_counter
      # e.g., UnicornMetrics.test_counter.increment
      #
      c.register(:counter, "test_counter")
      #
    end

Register a new counter,

    UnicornMetrics.configure do |c|
      c.register(:counter, "test_counter")
    end

Use it in the application

    >> counter = UnicornMetrics.test_counter

    # Getting the count
    >> counter.count
    #=> 0

    # Incrementing
    >> 5.times { counter.increment }
    >> counter.count
    #=> 5

    # Decrementing
    >> 5.times { counter.decrement }
    >> counter.count
    #=> 0

    # Resetting
    >> 5.times { counter.increment }
    >> counter.reset
    >> counter.count
    #=> 0

Timers

UnicornMetrics::Timer implements a Timer object that tracks elapsed time and ticks.

Register a new timer,

    UnicornMetrics.configure do |c|
      c.register(:timer, "test_timer")
    end

Use it in the application

    >> timer = UnicornMetrics.test_timer

    # Time some action
    >> elapsed_time = Benchmark.realtime { sleep(10) }

    # Record it in the timer
    >> timer.tick(elapsed_time)

    # Get the total elapsed time
    # We get 3 significant digits after the decimal point
    >> timer.sum
    => 10.001

    # Reset the timer
    >> timer.reset
    >> timer.sum
    => 0.0

HTTP Request/Response Counters and Request Timers

Register a UnicornMetrics::ResponseCounter or UnicornMetrics::RequestCounter to track the response status code or request method to a specified path.

    # Path is optional
    >> UnicornMetrics.register(:response_counter, "responses.2xx", /[2]\d{2}/)

    # Request counter with a 'path' argument
    >> UnicornMetrics.register(:request_counter, "requests.POST", 'POST', /^\/my_endpoint\/$/)

HTTP metrics must be enabled in the config file.

    # Rails.root/config/initializers/unicorn_metrics.rb

    UnicornMetrics.configure do |c|
      c.http_metrics = true #Default false
    end

This will give you these timers and counters for free: "responses.4xx", "responses.5xx", "responses.2xx", "responses.3xx" "requests.POST", "requests.PUT", "requests.GET", "requests.DELETE"

Middleware

Included middleware to support exposing metrics to an endpoint. These can then be consumed by a service that publishes to Graphite.

Important: this middleware builds upon the standard Raindrops middleware. It is currently set to provide the default Raindrops data as part of the metrics response

Add to the top of the middleware stack in config.ru:

    # config.ru

    require 'unicorn_metrics/middleware'
    use UnicornMetrics::Middleware, :path => "/metrics"
    # other middleware...
    run N::Application

Metrics will be published to the defined path (i.e., http://localhost:3000/metrics )

    {
      // A custom Request Timer added here
      // See example_config.rb
      "api/v1/custom/id.GET": {
        "type": "timer",
        "sum": 0.0,
        "value": 0
      },
      "responses.2xx": {
        "type": "counter",
        "value": 1
      },
      "responses.3xx": {
        "type": "counter",
        "value": 19
      },
      "responses.4xx": {
        "type": "counter",
        "value": 0
      },
      "responses.5xx": {
        "type": "counter",
        "value": 0
      },
      "requests.GET": {
        "type": "timer",
        "sum": 1.666,
        "value": 20
      },
      "requests.POST": {
        "type": "timer",
        "sum": 0.0,
        "value": 0
      },
      "requests.DELETE": {
        "type": "timer",
        "sum": 0.0,
        "value": 0
      },
      "requests.HEAD": {
        "type": "timer",
        "sum": 0.0,
        "value": 0
      },
      "requests.PUT": {
        "type": "timer",
        "sum": 0.0,
        "value": 0
      },
      "raindrops.calling": {
        "type": "gauge",
        "value": 0
      },
      "raindrops.writing": {
        "type": "gauge",
        "value": 0
      },
      // This will only work on Linux platforms as specified by the Raindrops::Middleware
      // Listeners on TCP sockets
      "raindrops.tcp.active": {
        "type": "gauge",
        "value": 0
      },
      // Listeners on Unix sockets
      "raindrops.unix.active": {
        "type": "gauge",
        "value": 0
      }
    }