#Safe Scale Plugin

The CF CLI Plugin uses blue-green deployment methodology to achieve continuous deployment. In addition to the regular blue-green deployment, the plugin also monitors endpoints. The user can provide a test endpoint that checks if the newly pushed app is healthy. They can also provide a transaction monitoring endpoint that checks if the old app instances are still processing transactions. Customers were noticing that when they scale down their applications, CF would shut down instances that were still processing transactions and they would be lost. This plugin will get the endpoints provided and prevent the blue-green deployment from either mapping the routes to an unhealthy app or prevent an old app that still has ongoing transactions from shutting down.

#Assumptions

The plugin makes assumptions about the endpoints provided by the user. Since the plugin accesses status codes to determine the state of the endpoint, the endpoints must use these status codes in order for the plugin to read it properly. For the test endpoint, it must return status code 200 if the app is healthy. For the transaction endpoint, it must return status code 204 (no content) if the app has no more transactions and 200 if there are still transactions processing. The plugin only consumes “https://“ endpoints currently.

The plugin requires you to be in the same directory as the app you are trying to blue-green deploy. The endpoints should be in the form of "/endpoint_name". Note- The endpoint test you provide needs to be monitoring the transactions of the entire app not the single instance of the app the plugin accesses.

cf safe-scale app_name new_app_name --inst=int --trans=string --test=string --timeout=int

Flags
inst: Number of instances of the new app
trans: endpoint to monitor if app still has pending transactions
test: endpoint to monitor if the app is healthy
timeout: time in seconds to monitor transactions

Note if you don’t provide an endpoint for monitoring transactions or checking health the plugin will just continue regular blue-green deployment

go get https://github.com/ezra-lieblich/safe-scale

cf install-plugin safe_scale