Rack request stats

rack-request_stats.gemspec

#!/usr/bin/env ruby

%w(lib shared).each do |dir|
  $LOAD_PATH.unshift(__dir__) unless $LOAD_PATH.include?(__dir__)
end

Gem::Specification.new do |spec|
  spec.name = "rack-request_stats"
  spec.version = "0.1.0"
  spec.authors = ["Jamie Gaskins"]
  spec.email = ["jgaskins@hey.com"]
  spec.summary = %q{Rack middleware to log request stats}
  spec.description = spec.summary
  spec.homepage = "https://gist.github.com/jgaskins/8fa816a78dc15b7c210fb0503b9ab1ff"
  spec.license = "MIT"

  spec.files = Dir["*.rb"]
  spec.executables = []
  spec.test_files = []
  spec.require_paths = ["."]

  spec.add_runtime_dependency "rack"
end

rack-request_stats.rb

require "rack"
require "logger"
require "thread"

class Rack::RequestStats
  VERSION = "0.1.0"

  attr_reader :logger

  Stats = Struct.new(:count, :requests_per_sec, :concurrent, keyword_init: true)

  def initialize(app, logger: Logger.new(STDOUT, level: Logger::INFO), log_every: nil, start_immediately: true)
    @app = app
    @logger = logger
    @count = 0
    @concurrent = 0
    @mutex = Mutex.new
    @log_every = if (log_every = log_every.to_i) == 0
                   1
                 else
                   log_every
                 end
    mark_last!

    start if start_immediately
  end

  def call(env)
    sync do
      @count += 1
      @concurrent += 1
    end
    @app.call env
  ensure
    sync { @concurrent -= 1 }
  end

  def start
    Thread.new do
      loop do
        sleep @log_every
        @logger.info stats
      rescue ex
        @logger.error ex.message
      end
    end
  end

  def stats
    last = sync { @last.tap { mark_last! } }

    stats = Stats.new(
      count: @count,
      requests_per_sec: @count.to_f / (@last - last),
      concurrent: @concurrent,
    )
    @count = 0
    stats
  end

  private def sync
    @mutex.synchronize { yield }
  end

  private def mark_last!
    @last = timestamp
  end

  private def timestamp
    Process.clock_gettime(Process::CLOCK_MONOTONIC)
  end
end

TIL: you can create a gem in a gist 🎉

usage: gem "rack-request_stats", gist: "jgaskins/8fa816a78dc15b7c210fb0503b9ab1ff"

Indeed. In fact, I’m even the one that added it to Bundler. 😄 rubygems/bundler@a3a3efa