Problem restarting Unicorn

Michael Guterl mguterl at gmail.com
Thu Apr 5 11:34:43 UTC 2012


On Thu, Apr 5, 2012 at 3:21 AM, Andrew Stewart
<boss at airbladesoftware.com> wrote:
> Hello,
>
> I seem to be confused about how to restart Unicorn when deploying updates to a Rails app via Capistrano.
>
> I just had a problem where a bundled gem wasn't being seen by the Unicorn processes, even though app code I introduced at the same time was being served by the Unicorn processes.  I had restarted Unicorn numerous times using `bundle exec cap deploy:restart` (see the code below), which I thought was the right way to do zero-downtime restarts, but my problem was only solved by doing a hard restart of Unicorn with `bundle exec cap deploy:hard_restart`.
>
> With each "normal" restart I tailed the stderr log to check everything was ok; everything appeared fine, with gems refreshed etc.
>
> Please could somebody explain what I'm doing wrong with my normal restarts?
>
> config/deploy.rb:
>
>    set :unicorn_config, "#{current_path}/config/unicorn.rb"
>    set :unicorn_pid,    "#{shared_path}/pids/unicorn.pid"
>
>    namespace :deploy do
>      task :start, :roles => :app, :except => { :no_release => true } do
>        run "cd #{current_path} && #{sudo_workaround} bundle exec unicorn -c #{unicorn_config} -E #{rails_env} -D"
>      end
>      task :stop, :roles => :app, :except => { :no_release => true } do
>        run "#{sudo_workaround} kill -s QUIT `cat #{unicorn_pid}`"
>      end
>      task :hard_stop, :roles => :app, :except => { :no_release => true } do
>        run "#{sudo_workaround} kill `cat #{unicorn_pid}`"
>      end
>      task :restart, :roles => :app, :except => { :no_release => true } do
>        run "#{sudo_workaround} kill -s USR2 `cat #{unicorn_pid}`"
>      end
>      task :hard_restart, :roles => :app, :except => { :no_release => true } do
>        hard_stop
>        start
>      end
>    end
>
>    # Works around Ubuntu changing the PATH when you use sudo.
>    # sudo's path can find common commands like echo but not much else.
>    def sudo_workaround
>      "sudo env PATH=$PATH"
>    end
>
>
> config/unicorn.rb:
>
>    APP_PATH = '/var/www/apps/sparkle'
>    worker_processes 4
>    user 'rails', 'rails'
>    working_directory "#{APP_PATH}/current"
>    listen "/tmp/unicorn_sparkle.sock", :backlog => 64
>    timeout 30
>    pid "#{APP_PATH}/shared/pids/unicorn.pid"
>    stderr_path "#{APP_PATH}/shared/log/unicorn.stderr.log"
>    stdout_path "#{APP_PATH}/shared/log/unicorn.stdout.log"
>    preload_app true
>    GC.respond_to?(:copy_on_write_friendly=) and GC.copy_on_write_friendly = true
>
>    before_fork do |server, worker|
>      defined?(ActiveRecord::Base) and ActiveRecord::Base.connection.disconnect!
>
>      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
>    end
>
>    after_fork do |server, worker|
>      defined?(ActiveRecord::Base) and ActiveRecord::Base.establish_connection
>    end
>
> This is all with Unicorn 4.2.0 and Rails 3.0.11.
>
> Many thanks in advance,
>

You probably want to check out the Sandbox documentation here:
http://unicorn.bogomips.org/Sandbox.html

The section that I think is most relevant is related to setting the START_CTX:

Unicorn::HttpServer::START_CTX[0] = "/some/path/to/bin/unicorn"

Hope that helps.

Best,
Michael Guterl


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