三种运行方式
不配置unicorn.rb的方式
unicorn_rails -D -l 0.0.0.0:3000 -E development
配置unicorn.rb的方式
unicorn_rails -c /path/to/app/config/unicorn.rb -D -E production
无缝重启方式，如nginx -s reload
kill -USR2 `cat path/to/app/tmp/pids/unicorn.pid`
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1.在Gemfile中加入

在Gemfile中加入以下一行。
gem 'unicorn'
在命令行中执行以下一行
bundle install

2.listen方式

listen 3000 # listen to port 3000 on all TCP interfaces
listen "127.0.0.1:3000"  # listen to port 3000 on the loopback interface
listen "/tmp/.unicorn.sock" # listen on the given Unix domain socket
listen "[::1]:3000" # listen to port 3000 on the IPv6 loopback interface

3.官方最小配置

listen 2007 # by default Unicorn listens on port 8080
worker_processes 2 # this should be >= nr_cpus
pid "/path/to/app/shared/pids/unicorn.pid"
stderr_path "/path/to/app/shared/log/unicorn.log"
stdout_path "/path/to/app/shared/log/unicorn.log"

4.官方最完整配置

# Sample verbose configuration file for Unicorn (not Rack)
#
# This configuration file documents many features of Unicorn
# that may not be needed for some applications. See
# https://bogomips.org/unicorn/examples/unicorn.conf.minimal.rb
# for a much simpler configuration file.
#
# See https://bogomips.org/unicorn/Unicorn/Configurator.html for complete
# documentation.

# Use at least one worker per core if you're on a dedicated server,
# more will usually help for _short_ waits on databases/caches.
worker_processes 4

# Since Unicorn is never exposed to outside clients, it does not need to
# run on the standard HTTP port (80), there is no reason to start Unicorn
# as root unless it's from system init scripts.
# If running the master process as root and the workers as an unprivileged
# user, do this to switch euid/egid in the workers (also chowns logs):
# user "unprivileged_user", "unprivileged_group"

# Help ensure your application will always spawn in the symlinked
# "current" directory that Capistrano sets up.
working_directory "/path/to/app/current" # available in 0.94.0+

# listen on both a Unix domain socket and a TCP port,
# we use a shorter backlog for quicker failover when busy
listen "/path/to/.unicorn.sock", :backlog => 64
listen 8080, :tcp_nopush => true

# nuke workers after 30 seconds instead of 60 seconds (the default)
timeout 30

# feel free to point this anywhere accessible on the filesystem
pid "/path/to/app/shared/pids/unicorn.pid"

# By default, the Unicorn logger will write to stderr.
# Additionally, ome applications/frameworks log to stderr or stdout,
# so prevent them from going to /dev/null when daemonized here:
stderr_path "/path/to/app/shared/log/unicorn.stderr.log"
stdout_path "/path/to/app/shared/log/unicorn.stdout.log"

# combine Ruby 2.0.0+ with "preload_app true" for memory savings
preload_app true

# Enable this flag to have unicorn test client connections by writing the
# beginning of the HTTP headers before calling the application.  This
# prevents calling the application for connections that have disconnected
# while queued.  This is only guaranteed to detect clients on the same
# host unicorn runs on, and unlikely to detect disconnects even on a
# fast LAN.
check_client_connection false

# local variable to guard against running a hook multiple times
run_once = true

before_fork do |server, worker|
  # the following is highly recomended for Rails + "preload_app true"
  # as there's no need for the master process to hold a connection
  defined?(ActiveRecord::Base) and
    ActiveRecord::Base.connection.disconnect!

  # Occasionally, it may be necessary to run non-idempotent code in the
  # master before forking.  Keep in mind the above disconnect! example
  # is idempotent and does not need a guard.
  if run_once
    # do_something_once_here ...
    run_once = false # prevent from firing again
  end

  # The following is only recommended for memory/DB-constrained
  # installations.  It is not needed if your system can house
  # twice as many worker_processes as you have configured.
  #
  # # This allows a new master process to incrementally
  # # phase out the old master process with SIGTTOU to avoid a
  # # thundering herd (especially in the "preload_app false" case)
  # # when doing a transparent upgrade.  The last worker spawned
  # # will then kill off the old master process with a SIGQUIT.
  # old_pid = "#{server.config[:pid]}.oldbin"
  # if old_pid != server.pid
  #   begin
  #     sig = (worker.nr + 1) >= server.worker_processes ? :QUIT : :TTOU
  #     Process.kill(sig, File.read(old_pid).to_i)
  #   rescue Errno::ENOENT, Errno::ESRCH
  #   end
  # end
  #
  # Throttle the master from forking too quickly by sleeping.  Due
  # to the implementation of standard Unix signal handlers, this
  # helps (but does not completely) prevent identical, repeated signals
  # from being lost when the receiving process is busy.
  # sleep 1
end

after_fork do |server, worker|
  # per-process listener ports for debugging/admin/migrations
  # addr = "127.0.0.1:#{9293 + worker.nr}"
  # server.listen(addr, :tries => -1, :delay => 5, :tcp_nopush => true)

  # the following is *required* for Rails + "preload_app true",
  defined?(ActiveRecord::Base) and
    ActiveRecord::Base.establish_connection

  # if preload_app is true, then you may also want to check and
  # restart any other shared sockets/descriptors such as Memcached,
  # and Redis.  TokyoCabinet file handles are safe to reuse
  # between any number of forked children (assuming your kernel
  # correctly implements pread()/pwrite() system calls)
end

5.GitHub配置

# unicorn_rails -c /data/github/current/config/unicorn.rb -E production -D

rails_env = ENV['RAILS_ENV'] || 'production'

# 16 workers and 1 master
worker_processes (rails_env == 'production' ? 16 : 4)

# Load rails+github.git into the master before forking workers
# for super-fast worker spawn times
preload_app true

# Restart any workers that haven't responded in 30 seconds
timeout 30

# Listen on a Unix data socket
listen '/data/github/current/tmp/sockets/unicorn.sock', :backlog => 2048


##
# REE

# http://www.rubyenterpriseedition.com/faq.html#adapt_apps_for_cow
if GC.respond_to?(:copy_on_write_friendly=)
  GC.copy_on_write_friendly = true
end


before_fork do |server, worker|
  ##
  # When sent a USR2, Unicorn will suffix its pidfile with .oldbin and
  # immediately start loading up a new version of itself (loaded with a new
  # version of our app). When this new Unicorn is completely loaded
  # it will begin spawning workers. The first worker spawned will check to
  # see if an .oldbin pidfile exists. If so, this means we've just booted up
  # a new Unicorn and need to tell the old one that it can now die. To do so
  # we send it a QUIT.
  #
  # Using this method we get 0 downtime deploys.

  old_pid = RAILS_ROOT + '/tmp/pids/unicorn.pid.oldbin'
  if File.exists?(old_pid) && server.pid != old_pid
    begin
      Process.kill("QUIT", File.read(old_pid).to_i)
    rescue Errno::ENOENT, Errno::ESRCH
      # someone else did our job for us
    end
  end
end


after_fork do |server, worker|
  ##
  # Unicorn master loads the app then forks off workers - because of the way
  # Unix forking works, we need to make sure we aren't using any of the parent's
  # sockets, e.g. db connection

  ActiveRecord::Base.establish_connection
  CHIMNEY.client.connect_to_server
  # Redis and Memcached would go here but their connections are established
  # on demand, so the master never opens a socket


  ##
  # Unicorn master is started as root, which is fine, but let's
  # drop the workers to git:git

  begin
    uid, gid = Process.euid, Process.egid
    user, group = 'git', 'git'
    target_uid = Etc.getpwnam(user).uid
    target_gid = Etc.getgrnam(group).gid
    worker.tmp.chown(target_uid, target_gid)
    if uid != target_uid || gid != target_gid
      Process.initgroups(user, target_gid)
      Process::GID.change_privilege(target_gid)
      Process::UID.change_privilege(target_uid)
    end
  rescue => e
    if RAILS_ENV == 'development'
      STDERR.puts "couldn't change user, oh well"
    else
      raise e
    end
  end
end

6.自定义配置一

module Rails
  class < 64

timeout 30

pid "#{Rails.root}/tmp/pids/unicorn.pid"

stderr_path "#{Rails.root}/log/unicorn.log"
stdout_path "#{Rails.root}/log/unicorn.log"

# combine Ruby 2.0.0dev or REE with "preload_app true" for memory savings
# http://rubyenterpriseedition.com/faq.html#adapt_apps_for_cow
preload_app true
GC.respond_to?(:copy_on_write_friendly=) and
  GC.copy_on_write_friendly = true

check_client_connection false

before_fork do |server, worker|
  # the following is highly recomended for Rails + "preload_app true"
  # as there's no need for the master process to hold a connection
  defined?(ActiveRecord::Base) and
    ActiveRecord::Base.connection.disconnect!

  old_pid = "#{server.config[:pid]}.oldbin"
  if File.exists?(old_pid) && old_pid != server.pid
    begin
      sig = (worker.nr + 1) >= server.worker_processes ? :QUIT : :TTOU
      Process.kill(sig, File.read(old_pid).to_i)
    rescue Errno::ENOENT, Errno::ESRCH
    end
  end

  # Throttle the master from forking too quickly by sleeping.  Due
  # to the implementation of standard Unix signal handlers, this
  # helps (but does not completely) prevent identical, repeated signals
  # from being lost when the receiving process is busy.
  sleep 1
end

after_fork do |server, worker|

  # the following is *required* for Rails + "preload_app true",
  defined?(ActiveRecord::Base) and
    ActiveRecord::Base.establish_connection

  # if preload_app is true, then you may also want to check and
  # restart any other shared sockets/descriptors such as Memcached,
  # and Redis.  TokyoCabinet file handles are safe to reuse
  # between any number of forked children (assuming your kernel
  # correctly implements pread()/pwrite() system calls)
end

7.自定义配置二

# -*- encoding: utf-8 -*-
user("menxu","menxu")


root_path = File.expand_path '../', File.dirname(__FILE__)
#log
log_file = root_path + '/log/unicorn.log'
err_log  = root_path + '/log/unicorn_error.log'


# process
pid_file = '/tmp/unicorn_padrino.pid'
old_pid = pid_file + '.oldbin'


#thron
socket_file = '/tmp/unicorn_padrino.sock'


worker_processes 2
working_directory root_path
timeout 30


#listen
listen 8080, tcp_nopush: false
listen socket_file, backlog: 1024


pid pid_file
stderr_path err_log
stdout_path log_file


preload_app true


before_exec do |server|
  ENV['BUNDLE_GEMFILE'] = root_path + '/Gemfile'
end


before_fork do |server, worker|
  if File.exists?(old_pid) && server.pid != old_pid
    begin
      Process.kill('QUIT', File.read(old_pid).to_i)
    rescue Errno::ENOENT, Errno::ESRCH
      puts "Send 'QUIT' signal to unicorn error!"
    end
  end
end

8.nginx.conf的配置

http {

  include mime.types;

  default_type application/octet-stream;

  sendfile on;

  keepalive_timeout 0;

  upstream app_server {
    # fail_timeout=0 means we always retry an upstream even if it failed
    # to return a good HTTP response (in case the Unicorn master nukes a
    # single worker for timing out).

    # for UNIX domain socket setups:
    server unix: /path/to/app/tmp/sockets/socket fail_timeout=0;
  }

  server {
        listen 8080 default;
        return 403; 
  }

  server {
    listen 8080;

    server_name www.explame.com;

    location / {
      proxy_pass http://app_server;
    }

    # Rails error pages
    error_page 500 502 503 504 /500.html;
    location = /500.html {
      root /path/to/app/current/public;
    }
  }
}

setsebool -P httpd_can_network_connect 1 

在进行Nginx+Tomcat 负载均衡的时候遇到了这个权限问题，在error.log日志中，我们可以看到如下：

connect() to 127.0.0.1:8080 failed (13: Permission denied) while connecting to upstream,

经过一番检查以及google,应该是SeLinux的导致的。可以选择一些两种方式进行：

1、关闭SeLinux,可以查看以下文章：

CentOS下查看SeLinux状态及关闭SeLinux

2、执行下面的命令

setsebool -P httpd_can_network_connect 1