Class: Telegraf::Rack

Inherits:
Object
  • Object
show all
Defined in:
lib/telegraf/rack.rb

Overview

Telegraf::Rack

This rack middleware collects request metrics and sends them to the telegraf agent. A ‘Point` data structure is added to the Rack environment to assign custom tags and values. This point can be accessed using the environment key defined in `::Telegraf::Rack::FIELD_NAME`.

Example:

if (point = request.env[::Telegraf::Rack::FIELD_NAME])
  point.tags[:tag] = 'tag'
  point.values[:value] = 10
end

Tags:

  • ‘status`:

    Response status unless request errored

Values:

  • ‘request_ms`:

    Total request processing time including response sending.

  • ‘app_ms`:

    Total application processing time.

  • ‘send_ms`:

    Time took to send the response body.

  • ‘queue_ms`:

    Queue time calculated from a `X-Request-Start` header if present. The
header is expected to be formatted like this `t=<timestamp>` and
contain a floating point timestamp in seconds.

Defined Under Namespace

Classes: Point

Constant Summary collapse

FIELD_NAME = 
'telegraf.rack.point'
HEADER_REGEX = 
/t=(\d+(\.\d+)?)/.freeze

Instance Method Summary collapse

Constructor Details

#initialize(app, agent:, series: 'rack', tags: {}, logger: nil) ⇒ Rack

rubocop:enable Lint/StructNewOverride



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# File 'lib/telegraf/rack.rb', line 55

def initialize(app, agent:, series: 'rack', tags: {}, logger: nil)
  @app = app
  @tags = tags.freeze
  @agent = agent
  @series = series.to_s.freeze
  @logger = logger
end

Instance Method Details

#call(env) ⇒ Object 



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# File 'lib/telegraf/rack.rb', line 63

def call(env)
  if (request_start = extract_request_start(env))
    queue_ms = (::Time.now.utc - request_start) * 1000 # milliseconds
  end

  rack_start = ::Rack::Utils.clock_time
  point = env[FIELD_NAME] = Point.new(@tags.dup, {})
  point.values[:queue_ms] = queue_ms if queue_ms

  begin
    begin
      status, headers, body = @app.call(env)
    ensure
      point.tags[:status] ||= status || -1
      point.values[:app_ms] = \
        (::Rack::Utils.clock_time - rack_start) * 1000 # milliseconds
    end

    send_start = ::Rack::Utils.clock_time
    proxy = ::Rack::BodyProxy.new(body) do
      point.values[:send_ms] = \
        (::Rack::Utils.clock_time - send_start) * 1000 # milliseconds

      finish(env, point, rack_start)
    end

    [status, headers, proxy]
  ensure
    finish(env, point, rack_start) unless proxy
  end
end