Q: Is `Execute` Async or Not ?

The docs say that Execute is synchronous but it is awaitable asks for a Task as a parameter.

Sorry if this sounds dumb due to my C# async experience but I am a bit confused. For example: does this make sense ?

policy.Execute(() => Task.Run(() => MyTask()));

[reisenberger]

To comment on: policy.Execute(() => Task.Run(() => MyTask())); : it doesn’t make sense.

• Task.Run(() => MyTask() on its own (disregarding Polly for a moment) creates and immediately returns a Task representing MyTask() running.

• The example doesn’t capture that Task into any variable to observe later, nor synchronously wait on its outcome (eg .Wait(), .Result), nor asynchronously await it. It thus creates an orphaned task which risks an UnobservedTaskException if MyTask() throws.

• policy.Execute(...) is synchronous, but it only governs Task.Run(...) near-immediately returning the Task representing MyTask() running. It won’t capture any exceptions thrown by MyTask(), nor (if that was desired) wait synchronously or asynchronously for MyTask() to complete.

Hope this helps!

[reisenberger]

Glad @cemremengu if it’s useful, and thanks for the doco idea! Since the async gotchas we’ve discussed are async general rather than specific to Polly, and already decently covered in the blogosphere/Stack Overflow, think I’ll keep the Polly doco purely Polly-focused. But: thanks for the idea!

If you’re looking for some good references on Task and async/await, some great starting points are:

• msdn on Task-based async
• Stephen Cleary’s Tour of Task blog posts (all parts)
• Stephen Cleary’s excellent book
• Alex Davies’ book

Cheers