Cancel in Retry Action

Is there a way to cancel additional retries within the retry action (synchronous)?

For example:

var policy = Policy
    .Handle<OfflineException>()
    .Retry(3, (ex, retryAttempt, ctx) =>
    {
        var result = MessageBox.Show("Please retry once the application is back online or cancel this request", "Application Offline", MessageBoxButtons.RetryCancel, MessageBoxIcon.Error);
        if (result != DialogResult.Retry)
        {
            //ToDo: cancel further attempts.  ctx.AbortRetries(); ??
        }
    });

When executing a cancellation token can be passed but one would not necessarily have access to the token source during the retry action.

[reisenberger]

Thanks @rodion-m for the comment.

A better solution here (which I missed pointing out originally) is that onRetry is not really the place to decide whether an action should be retried. Polly already offers a well-defined, strongly-expressive API for whether exceptions should be retried: the .Handle<>() clauses.

So @Discofunk 's original problem could also be solved by:

var policy = Policy
    .Handle<OfflineException>(_ => 
     {
        var result = MessageBox.Show("Please retry once the application is back online or cancel this request", "Application Offline", MessageBoxButtons.RetryCancel, MessageBoxIcon.Error);
        return (result == DialogResult.Retry);
    });
).Retry(3);

---

Thanks @rodion-m for the suggestion that sleepDurationProvider could return null to indicate “don’t retry”. Broadly, I am not in favour of having two places in an API to accomplish the same thing, as this tends to dilute the focus of the API overall (users will ask: “What is the difference?”). So, because Polly already has the strong API of the .Handle<>() clauses to indicate whether to retry exceptions, we will probably not modify sleepDurationProvider to also indicate this.

[rodion-m]

Hello guys! @reisenberger, sorry, but your solution looks like a hack. Please consider a solution with a nullable TimeSpan in the sleepDurationProvider and if it’s null, it means just Cancel (without any unnecessary exceptions).