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orange-cloudfoundry / cf-plugin-bg-restage

cf plugin for zero downtime application restaging
Apache License 2.0
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bg-restage

cf plugin for zero-downtime application restaging and restarting, highly inspired by autopilot.

cf bg-restage is mostly for those who don't want to redeploy an app with source code. It was initially created to restage automatically all apps in a Cloud Foundry when a new buildpack has been released with security patch.

cf bg-restart can be used, for example, to perform zero-downtime scale-up/down of instances, or to apply new environment variables, service bindings or security groups.

Installation

Download the latest version from the releases page and make it executable.

$ cf install-plugin path/to/downloaded/binary

Usage

$ cf bg-restage [--no-delete | --no-stop] application-to-restage
$ cf bg-restart [--no-delete | --no-stop] application-to-restart

Method

This is the process for bg-restage:

  1. It retrieves manifest from old app in a directory and create fake file as content to be pushed.

  2. The old application is renamed to <APP-NAME>-venerable. It keeps its old route mappings and this change is invisible to users.

  3. The new application is pushed to <APP-NAME>, this push will normally fail because we just want to create an app but not push real code (we do that because there is no easy way to create an app without pushing code as a cli plugin). Note: you will not see any failures and if it's not failed the app will not be started.

  4. Application bits (source code) will be copied from old app to the new app to put real code inside the new app.

  5. The new app will be restarted which will restage the app with the real code from old app.

  6. The old app will be removed and all traffic will be on the new app.

The process for bg-restart is similar, but in step 4. we also copy the staged droplet in addition to the application bits.