Class: Raindrops::Middleware

Inherits:
Object
  • Object
show all
Defined in:
lib/raindrops/middleware.rb

Overview

Raindrops::Middleware is Rack middleware that allows snapshotting current activity from an HTTP request. For all operating systems, it returns at least the following fields:

  • calling - the number of application dispatchers on your machine
  • writing - the number of clients being written to on your machine

Additional fields are available for Linux users.

It should be loaded at the top of Rack middleware stack before other middlewares for maximum accuracy.

Usage (Rainbows!/Unicorn preload_app=false)

If you're using preload_app=false (the default) in your Rainbows!/Unicorn config file, you'll need to create the global Stats object before forking.

require 'raindrops'
$stats ||= Raindrops::Middleware::Stats.new

In your Rack config.ru:

use Raindrops::Middleware, :stats => $stats

Usage (Rainbows!/Unicorn preload_app=true)

If you're using preload_app=true in your Rainbows!/Unicorn config file, just add the middleware to your stack:

In your Rack config.ru:

use Raindrops::Middleware

Linux-only extras!

To get bound listener statistics under Linux, you need to specify the listener names for your server. You can even include listen sockets for other servers on the same machine. This can be handy for monitoring your nginx proxy as well.

In your Rack config.ru, just pass the :listeners argument as an array of strings (along with any other arguments). You can specify any combination of TCP or Unix domain socket names:

use Raindrops::Middleware, :listeners => %w(0.0.0.0:80 /tmp/.sock)

If you're running Unicorn 0.98.0 or later, you don't have to pass in the :listeners array, Raindrops will automatically detect the listeners used by Unicorn master process. This does not detect listeners in different processes, of course.

The response body includes the following stats for each listener (see also Raindrops::ListenStats):

  • active - total number of active clients on that listener
  • queued - total number of queued (pre-accept()) clients on that listener

Demo Server

There is a server running this middleware (and Watcher) at https://yhbt.net/raindrops-demo/_raindrops

Also check out the Watcher demo at https://yhbt.net/raindrops-demo/

The demo server is only limited to 30 users, so be sure not to abuse it by using the /tail/ endpoint too much.

Defined Under Namespace

Classes: Proxy

Constant Summary collapse

Stats =

A Raindrops::Struct used to count the number of :calling and :writing clients. This struct is intended to be shared across multiple processes and both counters are updated atomically.

This is supported on all operating systems supported by Raindrops

Raindrops::Struct.new(:calling, :writing)

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(app, opts = {}) ⇒ Middleware

app may be any Rack application, this middleware wraps it. opts is a hash that understands the following members:

  • :stats - Raindrops::Middleware::Stats struct (default: Stats.new)
  • :path - HTTP endpoint used for reading the stats (default: "/_raindrops")
  • :listeners - array of host:port or socket paths (default: from Unicorn)


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# File 'lib/raindrops/middleware.rb', line 92

def initialize(app, opts = {})
  @app = app
  @stats = opts[:stats] || Stats.new
  @path = opts[:path] || "/_raindrops"
  tmp = opts[:listeners]
  if tmp.nil? && defined?(Unicorn) && Unicorn.respond_to?(:listener_names)
    tmp = Unicorn.listener_names
  end
  @tcp = @unix = nil

  if tmp
    @tcp = tmp.grep(/\A.+:\d+\z/)
    @unix = tmp.grep(%r{\A/})
    @tcp = nil if @tcp.empty?
    @unix = nil if @unix.empty?
  end
end

Instance Attribute Details

#app ⇒ Object

:nodoc:



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# File 'lib/raindrops/middleware.rb', line 73

def app
  @app
end

#path ⇒ Object

:nodoc:



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# File 'lib/raindrops/middleware.rb', line 73

def path
  @path
end

#stats ⇒ Object

:nodoc:



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# File 'lib/raindrops/middleware.rb', line 73

def stats
  @stats
end

#tcp ⇒ Object

:nodoc:



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# File 'lib/raindrops/middleware.rb', line 73

def tcp
  @tcp
end

#unix ⇒ Object

:nodoc:



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# File 'lib/raindrops/middleware.rb', line 73

def unix
  @unix
end

Instance Method Details

#call(env) ⇒ Object

standard Rack endpoint



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# File 'lib/raindrops/middleware.rb', line 111

def call(env) # :nodoc:
  env['PATH_INFO'] == @path and return stats_response
  begin
    @stats.incr_calling

    status, headers, body = @app.call(env)
    rv = [ status, headers, Proxy.new(body, @stats) ]

    # the Rack server will start writing headers soon after this method
    @stats.incr_writing
    rv
  ensure
    @stats.decr_calling
  end
end

#stats_response ⇒ Object

:nodoc:



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# File 'lib/raindrops/middleware.rb', line 127

def stats_response  # :nodoc:
  body = "calling: #{@stats.calling}\n" \
         "writing: #{@stats.writing}\n"

  if defined?(Raindrops::Linux.tcp_listener_stats)
    Raindrops::Linux.tcp_listener_stats(@tcp).each do |addr,stats|
      body << "#{addr} active: #{stats.active}\n" \
              "#{addr} queued: #{stats.queued}\n"
    end if @tcp
    Raindrops::Linux.unix_listener_stats(@unix).each do |addr,stats|
      body << "#{addr} active: #{stats.active}\n" \
              "#{addr} queued: #{stats.queued}\n"
    end if @unix
  end

  headers = {
    "Content-Type" => "text/plain",
    "Content-Length" => body.size.to_s,
  }
  [ 200, headers, [ body ] ]
end