Add experimental support for Puma

This allows us (and others) to test drive Puma without it affecting all
users. Puma can be enabled by setting the environment variable
"USE_PUMA" to a non empty value.

Gemfile

@@ -127,6 +127,11 @@ group :unicorn do
   gem 'unicorn-worker-killer', '~> 0.4.2'
 end
+group :puma do
+  gem 'puma', '~> 2.15', require: false
+  gem 'puma_worker_killer', require: false
+end
+
 # State machine
 gem "state_machines-activerecord", '~> 0.4.0'
 # Run events after state machine commits

Gemfile.lock

@@ -515,6 +515,10 @@ GEM
       slop (~> 3.4)
     pry-rails (0.3.4)
       pry (>= 0.9.10)
+    puma (2.15.3)
+    puma_worker_killer (0.0.4)
+      get_process_mem (~> 0.2)
+      puma (~> 2.7)
     pyu-ruby-sasl (0.0.3.3)
     quiet_assets (1.0.3)
       railties (>= 3.1, < 5.0)
@@ -945,6 +949,8 @@ DEPENDENCIES
   poltergeist (~> 1.9.0)
   premailer-rails (~> 1.9.0)
   pry-rails
+  puma (~> 2.15)
+  puma_worker_killer
   quiet_assets (~> 1.0.2)
   rack-attack (~> 4.3.1)
   rack-cors (~> 0.4.0)

config/initializers/puma.rb

+if ENV['USE_PUMA']
+  require 'puma'
+  require 'puma_worker_killer'
+
+  if Rails.env.production? or Rails.env.staging?
+    PumaWorkerKiller.config do |config|
+      config.ram       = 250
+      config.frequency = 5
+
+      # We just wan't to limit to a fixed maximum, unrelated to the total amount
+      # of available RAM.
+      config.percent_usage = 100.0
+
+      # Ideally we'll never hit the maximum amount of memory. If so the worker
+      # is restarted already, thus periodically restarting workers shouldn't be
+      # needed.
+      config.rolling_restart_frequency = false
+    end
+
+    PumaWorkerKiller.start
+  end
+end

config/puma.rb.example

+# The directory to operate out of.
+#
+# The default is the current directory.
+#
+directory '/home/git/gitlab'
+
+# Load "path" as a rackup file.
+#
+# The default is "config.ru".
+#
+rackup 'config.ru'
+
+# Daemonize the server into the background. Highly suggest that
+# this be combined with "pidfile" and "stdout_redirect".
+#
+# The default is "false".
+#
+# daemonize
+# daemonize false
+
+# Store the pid of the server in the file at "path".
+#
+pidfile '/home/git/gitlab/tmp/pids/puma.pid'
+
+# Use "path" as the file to store the server info state. This is
+# used by "pumactl" to query and control the server.
+#
+state_path '/home/git/gitlab/tmp/pids/puma.state'
+
+# Redirect STDOUT and STDERR to files specified. The 3rd parameter
+# ("append") specifies whether the output is appended, the default is
+# "false".
+#
+stdout_redirect '/home/git/gitlab/log/puma.stdout.log',
+  '/home/git/gitlab/log/puma.stderr.log',
+  true
+
+# Disable request logging.
+#
+# The default is "false".
+#
+# quiet
+
+# Configure "min" to be the minimum number of threads to use to answer
+# requests and "max" the maximum.
+#
+# The default is "0, 16".
+#
+threads 32, 64
+
+# Bind the server to "url". "tcp://", "unix://" and "ssl://" are the only
+# accepted protocols.
+#
+# The default is "tcp://0.0.0.0:9292".
+#
+# bind 'tcp://0.0.0.0:9292'
+# bind 'unix:///var/run/puma.sock'
+# bind 'unix:///var/run/puma.sock?umask=0111'
+# bind 'ssl://127.0.0.1:9292?key=path_to_key&cert=path_to_cert'
+bind 'unix:///home/git/gitlab/tmp/sockets/gitlab.socket'
+bind 'tcp://127.0.0.1:8080'
+
+# Instead of "bind 'ssl://127.0.0.1:9292?key=path_to_key&cert=path_to_cert'" you
+# can also use the "ssl_bind" option.
+#
+# ssl_bind '127.0.0.1', '9292', { key: path_to_key, cert: path_to_cert }
+
+# Code to run before doing a restart. This code should
+# close log files, database connections, etc.
+#
+# This can be called multiple times to add code each time.
+#
+# on_restart do
+#   puts 'On restart...'
+# end
+
+on_restart do
+  ActiveRecord::Base.connection.disconnect! if defined?(ActiveRecord::Base)
+end
+
+# Command to use to restart puma. This should be just how to
+# load puma itself (ie. 'ruby -Ilib bin/puma'), not the arguments
+# to puma, as those are the same as the original process.
+#
+# restart_command '/u/app/lolcat/bin/restart_puma'
+
+# === Cluster mode ===
+
+# How many worker processes to run.
+#
+# The default is "0".
+#
+workers 3
+
+# Code to run when a worker boots to setup the process before booting
+# the app.
+#
+# This can be called multiple times to add hooks.
+#
+# on_worker_boot do
+#   puts 'On worker boot...'
+# end
+
+on_worker_boot do
+  ActiveRecord::Base.establish_connection if defined?(ActiveRecord::Base)
+end
+
+# Code to run when a worker boots to setup the process after booting
+# the app.
+#
+# This can be called multiple times to add hooks.
+#
+# after_worker_boot do
+#   puts 'After worker boot...'
+# end
+
+# Code to run when a worker shutdown.
+#
+#
+# on_worker_shutdown do
+#   puts 'On worker shutdown...'
+# end
+
+# Allow workers to reload bundler context when master process is issued
+# a USR1 signal. This allows proper reloading of gems while the master
+# is preserved across a phased-restart. (incompatible with preload_app)
+# (off by default)
+
+# prune_bundler
+
+# Preload the application before starting the workers; this conflicts with
+# phased restart feature. (off by default)
+
+preload_app!
+
+# Additional text to display in process listing
+#
+tag 'GitLab Puma'
+
+#
+# If you do not specify a tag, Puma will infer it. If you do not want Puma
+# to add a tag, use an empty string.
+
+# Verifies that all workers have checked in to the master process within
+# the given timeout. If not the worker process will be restarted. Default
+# value is 60 seconds.
+#
+worker_timeout 60
+
+# Change the default worker timeout for booting
+#
+# If unspecified, this defaults to the value of worker_timeout.
+#
+# worker_boot_timeout 60
+
+# === Puma control rack application ===
+
+# Start the puma control rack application on "url". This application can
+# be communicated with to control the main server. Additionally, you can
+# provide an authentication token, so all requests to the control server
+# will need to include that token as a query parameter. This allows for
+# simple authentication.
+#
+# Check out https://github.com/puma/puma/blob/master/lib/puma/app/status.rb
+# to see what the app has available.
+#
+# activate_control_app 'unix:///var/run/pumactl.sock'
+# activate_control_app 'unix:///var/run/pumactl.sock', { auth_token: '12345' }
+# activate_control_app 'unix:///var/run/pumactl.sock', { no_token: true }
+#
+# vim: set ft=ruby: