Posted 8 months ago. Visible to the public.

Capistrano task to tail remote application logs of multiple servers

When your application is running on a multi-server setup, application logs are stored per server (unless you choose a centralized logging solution).
Here is a Capistrano task that connects to all servers and prints logs to your terminal like this:

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$ cap production app:logs 00:00 app:logs 01 tail -n0 -F /var/www/your-application/shared/log/production.log | while read line; do echo "$(hostname): $line"; done 01 app01-prod: Started GET "/sign_in" for 1.2.3.4 at 2018-04-26 11:28:19 +0200 01 app01-prod: Processing by Users::SessionsController#new as HTML 01 app01-prod: Rendering devise/sessions/new.haml within layouts/signed_out 01 app01-prod: Rendered devise/sessions/new.haml within layouts/signed_out (4.8ms) 01 app01-prod: Rendered layouts/shared/_head.haml (0.5ms) 01 app01-prod: Completed 200 OK in 8ms (Views: 6.1ms | ActiveRecord: 0.0ms) 01 app02-prod: Started GET "/messages/number_of_new" for 5.6.7.8 at 2018-04-26 11:28:20 +0200 01 app02-prod: Processing by MessagesController#number_of_new as */* 01 app02-prod: Rendering text template 01 app02-prod: Rendered text template (0.0ms) 01 app02-prod: Completed 200 OK in 23ms (Views: 1.0ms | ActiveRecord: 7.2ms)

Store the following task in a file like lib/capistrano/tasks/app.rake.

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namespace :app do desc 'Tail remote log files' task :logs do on roles :app do logfile = ENV['LOG'] || fetch(:rails_env) execute %(tail -n0 -F #{shared_path}/log/#{logfile}.log | while read line; do echo "$(hostname): $line"; done) end end end

If you have some other log file that you want to tail, use the LOG env variable, like LOG=sidekiq cap production app:logs.

Note that Capistrano truncates lines that are longer than your terminal. This can be painful when looking at logs, and we recommend you disable truncation entirely.

By refactoring problematic code and creating automated tests, makandra can vastly improve the maintainability of your Rails application.

Owner of this card:

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Arne Hartherz
Last edit:
8 months ago
by Arne Hartherz
About this deck:
We are makandra and do test-driven, agile Ruby on Rails software development.
License for source code
Posted by Arne Hartherz to makandra dev
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