From 90726e5187a9053c6eb7caf90ebec1d38d4372ea Mon Sep 17 00:00:00 2001
From: Eric Wong <normalperson@yhbt.net>
Date: Tue, 8 Mar 2011 14:18:11 -0800
Subject: preliminary Rack app to track last_data_recv

Seems to basically work
---
 lib/raindrops/last_data_recv.rb | 100 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 100 insertions(+)
 create mode 100644 lib/raindrops/last_data_recv.rb

(limited to 'lib/raindrops/last_data_recv.rb')

diff --git a/lib/raindrops/last_data_recv.rb b/lib/raindrops/last_data_recv.rb
new file mode 100644
index 0000000..3ec056e
--- /dev/null
+++ b/lib/raindrops/last_data_recv.rb
@@ -0,0 +1,100 @@
+# -*- encoding: binary -*-
+require "raindrops"
+
+# This is highly experimental!
+#
+# A self-contained Rack application for aggregating in the
+# +tcpi_last_data_recv+ field in +struct tcp_info+ if
+# /usr/include/linux/tcp.h.  This is only useful for Linux 2.6 and later.
+# This primarily supports Unicorn and derived servers, but may also be
+# used with any Ruby web server using the core TCPServer class in Ruby.
+#
+# Hitting the Rack endpoint configured for this application will return
+# a an ASCII histogram response body with the following headers:
+#
+# - X-Count   - number of requests received
+#
+# The following headers are only present if X-Count is greater than one.
+#
+# - X-Min     - lowest last_data_recv time recorded (in milliseconds)
+# - X-Max     - highest last_data_recv time recorded (in milliseconds)
+# - X-Mean    - mean last_data_recv time recorded (rounded, in milliseconds)
+# - X-Std-Dev - standard deviation of last_data_recv times
+# - X-Outliers-Low - number of low outliers (hopefully many!)
+# - X-Outliers-High - number of high outliers (hopefully zero!)
+#
+# == To use with Unicorn and derived servers (preload_app=false):
+#
+# Put the following in our Unicorn config file (not config.ru):
+#
+#   require "raindrops/last_data_recv"
+#
+# Then follow the instructions below for config.ru:
+#
+# == To use with any Rack server using TCPServer
+#
+# Setup a route for Raindrops::LastDataRecv in your Rackup config file
+# (typically config.ru):
+#
+#   require "raindrops"
+#   map "/raindrops/last_data_recv" do
+#     run Raindrops::LastDataRecv.new
+#   end
+#   map "/" do
+#     use SomeMiddleware
+#     use MoreMiddleware
+#     # ...
+#     run YourAppHere.new
+#   end
+#
+# == To use with any other Ruby web server that uses TCPServer
+#
+# Put the following in any piece of Ruby code loaded after the server has
+# bound its TCP listeners:
+#
+#   ObjectSpace.each_object(TCPServer) do |s|
+#     s.extend Raindrops::Aggregate::LastDataRecv
+#   end
+#
+#   Thread.new do
+#     Raindrops::Aggregate::LastDataRecv.default_aggregate.master_loop
+#   end
+#
+# Then follow the above instructions for config.ru
+#
+class Raindrops::LastDataRecv
+  # :stopdoc:
+
+  # trigger autoloads
+  if defined?(Unicorn)
+    agg = Raindrops::Aggregate::LastDataRecv.default_aggregate
+    AGGREGATE_THREAD = Thread.new { agg.master_loop }
+  end
+  # :startdoc
+
+  def initialize(opts = {})
+    Raindrops::Aggregate::LastDataRecv.cornify! if defined?(Unicorn)
+    @aggregate =
+      opts[:aggregate] || Raindrops::Aggregate::LastDataRecv.default_aggregate
+  end
+
+  def call(_)
+    a = @aggregate
+    count = a.count
+    headers = {
+      "Content-Type" => "text/plain",
+      "X-Count" => count.to_s,
+    }
+    if count > 1
+      headers["X-Min"] = a.min.to_s
+      headers["X-Max"] = a.max.to_s
+      headers["X-Mean"] = a.mean.round.to_s
+      headers["X-Std-Dev"] = a.std_dev.round.to_s
+      headers["X-Outliers-Low"] = a.outliers_low.to_s
+      headers["X-Outliers-High"] = a.outliers_high.to_s
+    end
+    body = a.to_s
+    headers["Content-Length"] = body.size.to_s
+    [ 200, headers, [ body ] ]
+  end
+end
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