Cloud SQL connection problem

[bruce]

I'm seeing the dreaded socket connection error in my application, deploying to the flex environment.

Postgrex.Protocol (#PID<0.1788.0>) failed to connect: ** (DBConnection.ConnectionError) tcp connect (/cloudsql/<project>:us-east1:stagingdb/.s.PGSQL.5432): no such file or directory - :enoent
... many more like it

I'm using postgrex v0.13.5, and the content of my app.yaml looks like:

env: flex
runtime: gs://elixir-runtime/elixir.yaml
runtime_config:
  release_app: <app-name>
env_variables:
  # ... other vars                   
  POSTGRES_SOCKET_DIR: "/cloudsql/<project>:us-east1:stagingdb"

I'm using Postgrex' :socket_dir option, which they recommend. I've also tried it with the :socket option set to the full path, /cloudsql/<project>:us-east1:stagingdb/.s.PGSQL.5432, to no avail.

I've enabled all the Cloud SQL APIs I could find for my project, and my <project>@appspot.gserviceaccount.com account is configured with both Editor and Cloud SQL Admin roles in IAM.

If anyone has any ideas, I'd be very helpful. (I'd really like to just hop into the instance and see exactly what is/isn't in /cloudsql, but I can't figure out how to do that.)

[bruce]

I appear to be able to connect after adding the following to my app.yaml; I assumed this was only necessary for old App Engine/Cloud SQL integrations:

beta_settings:
  cloud_sql_instances: <INSTANCE-NAME>