Class: Lens::Rails::MetricsExporter

Inherits:
Object
  • Object
show all
Defined in:
lib/lens/rails/metrics_exporter.rb

Overview

Rack middleware that tracks request counts and durations, flushing aggregated metrics to POST /v1/metrics every 30s via a persistent HTTPS connection.

Constant Summary collapse

RESERVOIR_SIZE = 
1024
FLUSH_INTERVAL = 
30

Instance Method Summary collapse

Constructor Details

#initialize(app, url:, token:, service_name:, open_timeout: 2, read_timeout: 2) ⇒ MetricsExporter

Returns a new instance of MetricsExporter.



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# File 'lib/lens/rails/metrics_exporter.rb', line 16

def initialize(app, url:, token:, service_name:,
  open_timeout: 2,
  read_timeout: 2)
  @app = app
  @token = token
  @service_name = service_name
  @uri = URI("#{url}/v1/metrics")
  @open_timeout = open_timeout
  @read_timeout = read_timeout
  @mutex = Mutex.new
  @http = nil
  reset_window
  start_flush_thread
  Lens::Rails.register_flushable(self)
end

Instance Method Details

#call(env) ⇒ Object 



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# File 'lib/lens/rails/metrics_exporter.rb', line 32

def call(env)
  Thread.current[:lens_request_id] = env["action_dispatch.request_id"]
  wall_start = Time.now
  start = Process.clock_gettime(Process::CLOCK_MONOTONIC)
  status, headers, body = @app.call(env)
  duration = (Process.clock_gettime(Process::CLOCK_MONOTONIC) - start) * 1000.0
  queue_time = parse_queue_time(env, wall_start)

  @mutex.synchronize do
    @request_count += 1
    @error_count += 1 if status >= 500
    @duration_sum += duration
    @duration_min = duration if @duration_min.nil? || duration < @duration_min
    @duration_max = duration if @duration_max.nil? || duration > @duration_max
    if @samples.size < RESERVOIR_SIZE
      @samples << duration
    else
      idx = rand(@request_count)
      @samples[idx] = duration if idx < RESERVOIR_SIZE
    end
    if queue_time
      @queue_samples << queue_time
      @queue_sum += queue_time
    end
  end

  [status, headers, body]
ensure
  Thread.current[:lens_request_id] = nil
end

#restart_flush_thread ⇒ Object 



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# File 'lib/lens/rails/metrics_exporter.rb', line 69

def restart_flush_thread
  begin
    @flush_thread&.kill
  rescue
    nil
  end
  close_http
  start_flush_thread
end

#shutdown(timeout:) ⇒ Object 



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# File 'lib/lens/rails/metrics_exporter.rb', line 63

def shutdown(timeout:)
  @flush_thread&.kill
  Thread.new { flush }.join(timeout)
rescue
end