Deployment system for Yesod (and other Haskell) web apps.

Components:

• Port assigner. Ask it for a new port, and notify it when a port is no longer in use.

• Logger: provides a file descriptor to redirect output to. Takes the name of the app.

• Process: Give it all the information (executable, working directory, environment, args) for a process, and it will start the process and monitor it. If the process dies, it will restart. Binds the output to the logger. Allows you to terminate the process.

• Postgres: Ask it for database information for an app. If no information is available, it will create a database/user.

• Nginx: Send it commands to add/modify/remove a virtual host. It will write the config file and reload nginx.

• App: Started with a path to an app bundle. Unpacks into a random folder inside the temp folder, gets a random port, starts a Process, updates Nginx, and waits for commands. Accepts two commands: reload and terminate.

  • Terminate kills the existing process, removes from Nginx, and deletes the folder.

  • Reload gets a new random port, unpacks to a new folder in the temp folder, starts a Process, waits till the process is "ready" (checks with an HTTP request)- canceling after a certain timeout.

    • If process is not ready within timeout, terminate the new process and delete the new folder.

    • If a process is ready, tell Nginx to use the new port, wait some amount of time (20 seconds?), send a TERM to the old process, wait some more (1 minute?) and delete the old folder.

• Keter: Delete temp folder, start the Nginx, logger, and port assigner. Start a new App for each app in the incoming folder. Monitor for file changes in the incoming folder, and appropriately start a new app, reload an existing app, or delete an existing app. Also provide a web interface based on logger.