Issue 4234 - Migrate Discourse to a Docker-based setup

modules/discourse/templates/app.yml.erb

+## this is the all-in-one, standalone Discourse Docker container template
+##
+## After making changes to this file, you MUST rebuild
+## /var/discourse/launcher rebuild app
+##
+## BE *VERY* CAREFUL WHEN EDITING!
+## YAML FILES ARE SUPER SUPER SENSITIVE TO MISTAKES IN WHITESPACE OR ALIGNMENT!
+## visit http://www.yamllint.com/ to validate this file as needed
+
+templates:
+  - "templates/postgres.template.yml"
+  - "templates/redis.template.yml"
+  - "templates/web.template.yml"
+  - "templates/web.ratelimited.template.yml"
+  - "templates/web.socketed.template.yml"
+
+## which TCP/IP ports should this container expose?
+expose:
+
+params:
+  db_default_text_search_config: "pg_catalog.english"
+
+  ## Set db_shared_buffers to a max of 25% of the total memory.
+  ## will be set automatically by bootstrap based on detected RAM, or you can override
+  db_shared_buffers: "256MB"
+
+  ## can improve sorting performance, but adds memory usage per-connection
+  #db_work_mem: "40MB"
+
+  ## Which Git revision should this container use? (default: tests-passed)
+  version: v1.5.3
+
+env:
+  LANG: en_US.UTF-8
+  RUBY_GC_MALLOC_LIMIT: 90000000
+
+  ## How many concurrent web requests are supported? Depends on memory and CPU cores.
+  ## will be set automatically by bootstrap based on detected CPUs, or you can override
+  UNICORN_WORKERS: 2
+
+  ## The domain name this Discourse instance will respond to
+  DISCOURSE_HOSTNAME: '<%= @domain %>'
+
+  ## Uncomment if you want the container to be started with the same
+  ## hostname (-h option) as specified above (default "$hostname-$config")
+  #DOCKER_USE_HOSTNAME: true
+
+  ## TODO: List of comma delimited emails that will be made admin and developer
+  ## on initial signup example 'user1@example.com,user2@example.com'
+  DISCOURSE_DEVELOPER_EMAILS: '<% @admins.each do |admin| %><%= admin %>,<% end %>'
+
+  ## TODO: The SMTP mail server used to validate new accounts and send notifications
+  DISCOURSE_SMTP_ADDRESS: localhost                # required
+  DISCOURSE_SMTP_PORT: 25                          # (optional, default 587)
+  #DISCOURSE_SMTP_USER_NAME: user@example.com      # required
+  #DISCOURSE_SMTP_PASSWORD: pa$$word               # required, WARNING the char '#' in pw can cause problems!
+  DISCOURSE_SMTP_ENABLE_START_TLS: false           # (optional, default true)
+
+  ## If you added the Lets Encrypt template, uncomment below to get a free SSL certificate
+  #LETSENCRYPT_ACCOUNT_EMAIL: me@example.com
+
+  ## The CDN address for this Discourse instance (configured to pull)
+  ## see https://meta.discourse.org/t/14857 for details
+  #DISCOURSE_CDN_URL: //discourse-cdn.example.com
+
+## The Docker container is stateless; all data is stored in /shared
+volumes:
+  - volume:
+      host: /var/discourse/shared/standalone
+      guest: /shared
+  - volume:
+      host: /var/discourse/shared/standalone/log/var-log
+      guest: /var/log
+
+## Plugins go here
+## see https://meta.discourse.org/t/19157 for details
+hooks:
+  after_code:
+    - exec:
+        cd: $home/plugins
+        cmd:
+          #- git clone https://github.com/discourse/docker_manager.git
+
+## Any custom commands to run after building
+run:
+  - exec: echo "Beginning of custom commands"
+  - exec: rails r "<% @site_settings.sort_by { |k,v| k }.each do |name, value| %>SiteSetting.<%=name%>='<%=value%>';<% end %>"
+  - exec: echo "End of custom commands"