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85 lines
2.7 KiB
Markdown
85 lines
2.7 KiB
Markdown
---
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title: What is Capistrano?
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layout: default
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---
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### Capistrano is a remote server automation tool.
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It supports the scripting and execution of arbitrary tasks, and includes a set of sane-default deployment workflows.
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Capistrano can be used to:
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* Reliably deploy web application to any number of machines simultaneously,
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in sequence or as a rolling set
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* To automate audits of any number of machines (checking login logs,
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enumerating uptimes, and/or applying security patches)
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* To script arbitrary workflows over SSH
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* To automate common tasks in software teams.
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* To drive infrastructure provisioning tools such as *chef-solo*, *Ansible* or similar.
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Capistrano is also *very* scriptable, and can be integrated with any other
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Ruby software to form part of a larger tool.
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#### What does it look like?
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#### What else is in the box?
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There's lots of cool stuff in the Capistrano toy box:
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* Interchangeable output formatters (progress, pretty, html, etc)
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* Easy to add support for other source control management software.
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* A rudimentary multi-console for running Capistrano interactively.
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* Host and Role filters for partial deploys, or partial-cluster maintenance.
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* Recipes for the Rails asset pipelines, and database migrations.
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* Support for complex environments.
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* A sane, expressive API:
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```ruby
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desc "Show off the API"
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task :ditty do
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on roles(:all) do |host|
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# Capture output from the remote host, and re-use it
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# we can reflect on the `host` object passed to the block
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# and use the `info` logger method to benefit from the
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# output formatter that is selected.
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uptime = capture('uptime')
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if host.roles.include?(:web)
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info "Your webserver #{host} has uptime: #{uptime}"
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end
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end
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on roles(:app) do
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# We can set environmental variables for the duration of a block
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# and move the process into a directoy, executing arbitrary tasks
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# such as letting Rails do some heavy lifting.
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with({:rails_env => :production}) do
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within('/var/www/my/rails/app') do
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execute :rails, :runner, 'MyModel.something'
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end
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end
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end
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on roles(:db) do
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# We can even switch users, provided we have support on the remote
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# server for switching to that user without being prompted for a
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# passphrase.
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as 'postgres' do
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widgets = capture "echo 'SELECT * FROM widgets;' | psql my_database"
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if widgets.to_i < 50
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warn "There are fewer than 50 widgets in the database on #{host}!"
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end
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end
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end
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on roles(:all) do
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# We can even use `test` the way the Unix gods intended
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if test("[ -d /some/directory ]")
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info "Phew, it's ok, the directory exists!"
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end
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end
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end
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```
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