injected db credentials change when I deploy new app version to cloud - postgresql

Question

I deploy a web app to a local cloudfoundry environment. As a database service for my DEV environment I have chosen a Marketplace service google-cloudsql-postgres with the plan postgres-db-f1-micro. Using the Web UI I created an instance with the name myapp-test-database and mentioned it in the CF Manifest:
applications:
- name: myapp-test
services:
- myapp-test-database
At first, all is fine. I can even redeploy the existing artifact. However, when I build a new version of my app and push it to CF, the injected credentials are updated and the app can no longer access the tables:
PSQLException: ERROR: permission denied for table
The tables are still there, but they're owned by the previous user. They were automatically created by the ORM in the public schema.
While the -OLD application still exists I can retrieve the old username/password from the CF Web UI or $VCAP_SERVICES and drop the tables.
Is this all because of Rolling App Deployments? But then there should be a lot of complaints.

Answer 1

If you are strictly doing a cf push (or restart/restage), the broker isn't involved (Cloud Controller doesn't talk to it), and service credentials won't change.
The only action through cf commands that can modify your credentials is doing an unbind followed by a bind. Many, but not all, service brokers will throw away credentials on unbind and provide new, unique credentials for a bind. This is often desirable so that you can rotate credentials if credentials are compromised.
Where this can be a problem is if you have custom scripts or cf cli plugins to implement rolling deployments. Most tools like this will use two separate application instances, which means you'll have two separate bindings and two separate sets of credentials.
If you must have one set of credentials you can use a service key to work around this. Service keys are like bindings but not associated with an application in CloudFoundry.
The downside of the service key is that it's not automatically exposed to your application, like a binding, through $VCAP_SERVICES. To workaround this, you can pass the service key creds into a user-provided service and then bind that to your application, or you can pass them into your application through other environment variables, like DB_URL.
The other option is to switch away from using scripts and cf cli plugins for blue/green deployment and to use the support that is now built into Cloud Foundry. With cf cli version 7+, cf push has a --strategy option which can be set to rolling to perform a rolling deployment. This does not create multiple application instances and so there would only ever exist one service binding and one set of credentials.

Answer 2

Request a static username using the extra bind parameter "username":
cf bind-service my-app-test-CANDIDATE myapp-test-database -c "{\"username\":\"myuser\"}"
With cf7+ it's possible to add parameters to the manifest:
applications:
- name: myapp-test
services:
- name: myapp-test-database
parameters: { "username": "myuser" }
https://docs.cloudfoundry.org/devguide/services/application-binding.html#arbitrary-params-binding
Note: Arbitrary parameters are not supported in app manifests in cf CLI v6.x. Arbitrary parameters are supported in app manifests in cf CLI v7.0 and later.
However, I can't find the new syntax here: https://docs.cloudfoundry.org/devguide/deploy-apps/manifest-attributes.html#services-block . The syntax I use comes from some other SO question.