disconnected: ** (DBConnection.ConnectionError) client #PID<[XXX]> exited

[jonleighton]

I thought I'd share that I've been working recently on fixing a flakey Wallaby test that was sometimes failing on CI with the above error.

I managed to isolate the cause, which is explained here: elixir-ecto/db_connection#247

TL;DR: when a browser aborts a request, the Cowboy2 server kills the process tree associated with that request. If a database connection (shared via Phoenix.Ecto.SQL.Sandbox) was in use at that time, the connection would become corrupted. After that, future requests, and the test that owns the connection, would be unable to use it.

Here's a test which reproduces the situation: jonleighton/db_connection_ownership_bug@922bbd8

And a fix has already gone into phoenix_ecto, so this shouldn't happen in future releases: phoenixframework/phoenix_ecto@1d8d28a

[mhanberg]

Thanks!