DBConnection.ConnectionError sometimes raise, sometimes returned

[jvf]

Due to a crash of the database server I see lots of (concurrent) queries failing with %DBConnection.ConnectionError{message: "connection not available and request was dropped from queue ...}. In some of the cases the ConnectionError is returned as an :error tuple and in other cases the error is raised by DBConnection. Is this intended by behaviour? If so, what does returning an :error tuple vs raising indicate?

[josevalim]

How are you using DBConnection? The error tuple is usually controlled by whatever is wrapping DBConnection. So if you are using Ecto, the tuple is for validations and so on.

[jvf]

I am using DBConnection through Xandra.

The error tuple is usually controlled by whatever is wrapping DBConnection.

Do I understand you correctly: DBConnection always throws, i.e. if I see it wrapped in en error tuple this has to come Xandra?

[josevalim]

Exactly!

[jvf]

Thank you for explaining!