Rails + unicorn Configuration

1. Basic Configuration

When unicorn is configured, there are two cases:

preload_app truepreload_app false

If preload_app is false, the unicorn master does not pre-load the entire rails app environment, and every worker executes the entire rails app.

When preload_app is true, the master of Unicorn loads the rails app environment in advance. In the case of copy_on_write_friendly, each worker replicates data from the master when executing the write operation (Resource Saving ).

If prelad_app is true, you need to disable the database connection in before_fork, because the master does not need to maintain this connection.

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!end

However, after after_fork, You need to reconnect to the database connection for each worker;

after_fork do |server, worker|  # the following is *required* for Rails + "preload_app true",  defined?(ActiveRecord::Base) and     ActiveRecord::Base.establish_connectionend

When there are other socket connections, you also need to reconnect in after_fork, or close in before_fork first, and then reconnect in after_fork.

2. Unicorn Signal

kill -s HUP pid

When preload_app is false, the configuration and rails app will be re-loaded, and all modified code will be re-loaded, because every worker will re-Execute

When preload_app is true, the configuration will be re-loaded, but the rails app will not be re-loaded. Because every worker is copied from the master, the modified Code will not be re-loaded.

The following command is required:

kill -s USR2 pid

In addition, the old unicorn process is automatically disabled in before_fork.

Before_fork do | Server, worker | # It will be executed when kill-s usr2 'oldpid 'is executed, because unicorn adds the original PID file name. oldbin suffix old_pid = "# {server. config [: 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 puts "Send 'quit' signal to Unicorn error! "End end

The result is unicorn again, a new process is generated, and the old process is disabled.