Could we have DBConnection.ConnectionError show us which Repo did it tried to check out?

[georgeguimaraes]

DBConnection.ConnectionError: connection not available and request was dropped from queue after 403ms. This means requests are coming in and your connection pool cannot serve them fast enough. You can address this by:

  1. Ensuring your database is available and that you can connect to it
  2. Tracking down slow queries and making sure they are running fast enough
  3. Increasing the pool_size (although this increases resource consumption)
  4. Allowing requests to wait longer by increasing :queue_target and :queue_interval

See DBConnection.start_link/2 for more information

  File "lib/db_connection.ex", line 1088, in DBConnection.transaction/3
  ....

I can assume the Repo based on the file/line from the stack trace, but is there a way for ConnectionError to know the name of the Repo and show us in the title? Would be very helpful. We have 4 Repos, 2 for the same database.

Would you be interested in a PR?

[josevalim]

The problem is that the concept of repository is completely orthogonal to DBConnection. I know the telemetry event [:db_connection, :connection_error] does include the options (which should include the repo), is that enough for your purposes?

[wojtekmach]

We might be able to use process labels but we'd have to pass them through ecto -> ecto_sql -> postgrex -> db_connection and then whoever is raising the exception, the pool I guess?, could include them in the exception message?

[josevalim]

Ah yes, we could support a :label option, but then that would need to be passed from Ecto to Postgrex/MyXQL/etc. I think that's a good idea.