bg-change-stack

cf plugin for zero downtime application stack change, highly inspired by cf-plugin-bg-restage & stack auditor.

Use this plugin when your CF environment doesn't support ZDT restart. When the CAPI doesn't support ZDT, the stack auditor plugin does a restart with down time, after changing stack. This plugin attempts to do a zero downtime stack change by leveraging bg-restage logics & stack auditor logics.

Installation

git clone https://github.com/naridnevahgar/cf-bg-change-stack.git
cd cf-bg-change-stack
./bin/build.sh
./bin/install_plugin.sh

Platform specific binary

To generate platform specific binary, use the build-all script available under build directory.

cd cf-bg-change-stack
./bin/build-all.sh

Usage

$ cf bg-change-stack <app name> <new stack name>

Method

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 failed 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. Bits 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 new app's stack will be changed using the /v3/apps endpoint.

7. The new app will be restarted again for the new stack to take effect.

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