[jon-wood]

The Erlang VM is built around message passing, so in the case of a dropped database connection your application code would pass a message to the database API asking for the results of a SQL query. The database API is currently trying to reconnect, so it’s not processing that queue of messages, but once it gets there it’ll pick up the message, run the query, and then send one back to the process that asked. This is all largely transparent to your application code, beyond being able to set some preferences in your return message handler around things like how long you’re willing to wait.

The whole “let it crash” thing comes from Erlang’s process supervision - in practice the DB API isn’t actually retrying. It’s continually failing to connect and if it can’t the process just crashes. The supervisor then notices and starts a new process in its place, this continues until either a process successfully starts or the configured retry count is hit. If the retry count is exceeded then the supervisor crashes, either taking the entire application with it, or more commonly being restarted itself by the next supervisor up the tree.