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PONginx rolling restart of Rails app with capistrano
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copied!<p>For the life of me I can't figure out how to make this work properly.</p> <p>The problem is similar to what others have, such as: <a href="https://stackoverflow.com/questions/124250/how-to-do-a-rolling-restart-of-a-cluster-of-mongrels">How to do a rolling restart of a cluster of mongrels</a></p> <p>We, however, are using Nginx/Passenger instead of Mongrel.</p> <p>The issue is that on a deploy if we use this standard :restart task:</p> <pre><code>task :restart, :roles => [:app], :except => {:no_release => true} do run "cd #{deploy_to}/current && touch tmp/restart.txt" end </code></pre> <p>It touches the restart.txt file across every web server, but any passenger instances currently serving requests need to finish before the new ones are spawned it seems. This creates a serious delay and causes our app to be unavailable for up to 2 minutes while everything is coming back up.</p> <p>In order to get around that the plan is to do the following:</p> <ol> <li>deploy code</li> <li>go to server 1, remove it from the load balancer</li> <li>restart nginx-passenger on server 1</li> <li>wait 60 seconds</li> <li>add server 1 back to load balancer</li> <li>go to server 2 (repeat steps 3 - 5)</li> </ol> <p>To accomplish this, I attempted this:</p> <p>(lb.txt is the file that the load balancer looks for)</p> <pre><code>task :restart, :roles => [:app], :except => {:no_release => true} do servers = find_servers_for_task(current_task) servers.map do |s| run "cd #{deploy_to}/current && echo '' > public/lb.txt", :host => s.host run %Q{rvmsudo /etc/init.d/nginx-passenger restart > /dev/null}, :host => s.host sleep 60 run "cd #{deploy_to}/current && echo 'ok' > public/lb.txt", :host => s.host end end </code></pre> <p>This <em>almost</em> works, however, during the deploy it seemed to run the loop through the servers once per servers listed in the :app role. We currently have 6 app servers, so the loop runs 6 times, restarting nginx-passenger 6 times per server.</p> <p>I just need this loop to run through one time.</p> <p>I know it seems that eventually passenger will get rolling restarts, but they do not seem to exist yet.</p> <p>If it helps, we are using Capistrano 2.x and Rails 3</p> <p>Any help would be great.</p> <p>Thanks.</p>

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