With the retry options in durable functions, what happens after the last attempt?

Question

I'm using a durable function that's triggered off a queue. I'm sending messages off the queue to a service that is pretty flaky, so I set up the RetryPolicy. Even still, I'd like to be able to see the failed messages even if the max retries has been exhausted.

Do I need to manually throw those to a dead-letter queue (and if so, it's not clear to me how I know when a message has been retried any number of times), or will the function naturally throw those to some kind of dead-letter/poison queue?

score 2 · Answer 1 · answered Feb 07 '19 at 19:57

When an activity fails in Durable Functions, an exception is marshalled back to the orchestration with FunctionFailedException thrown. It doesn't matter whether you used automatic retry or not - at the very end, the whole activity fails and it's up to you to handle the situation. As per documentation:

try
{
    await context.CallActivityAsync("CreditAccount",
        new
        {
            Account = transferDetails.DestinationAccount,
            Amount = transferDetails.Amount
        });
}
catch (Exception)
{
    // Refund the source account.
    // Another try/catch could be used here based on the needs of the application.
    await context.CallActivityAsync("CreditAccount",
        new
        {
            Account = transferDetails.SourceAccount,
            Amount = transferDetails.Amount
        });
}

The only thing retry changes is handling the transient error(so you do not have to enable the safe route each time you have e.g. network issues).

With the retry options in durable functions, what happens after the last attempt?

1 Answers1