Does Polly Bulkhead policy itself place calls onto threads?

Question

I have the following Polly policies defined:

sharedBulkhead = Policy.Bulkhead(maxParallelizations, maxQueuingActions);
resilienceStrategy = Policy.Wrap(retryPolicy, circuitBreaker, sharedBulkhead);
policyWrap = fallbackForAnyException.Wrap(fallbackForCircuitBreaker.Wrap(resilienceStrategy));

I execute the policy like so:

public bool Notify(IGrouping<string, TModel> messages)
    {
        var endPoint = messages.Key;
        Task.Run(() =>
        {
            foreach (var message in messages)
            {
                policyWrap.Execute((context) => CallApi(endPoint), new Context(endPoint));
            }
        });

        return true;
    }

I want each call to Notify() to run on a new thread. So, my question is: Do I have to explicitly call Task.Run(() => for a new thread, or is that automatically run on a new thread by polly?

Hi Nimish. We are going to need some background as your objective is not obvious from the question title or description. What problem are you trying to solve here? — Gusdor, Dec 17 '18 at 18:16
I want to know if what I am doing is right? Do I have to execute the policy inside a thread created explicitly? — Clairvoyant, Dec 17 '18 at 18:29
As api calls are I/O bound, I would not wrap them in `Task.Run`. You might prefer [the async version of Execute](https://github.com/App-vNext/Polly/wiki/Asynchronous-action-execution) — Crowcoder, Dec 17 '18 at 18:45
If the call to be governed by the Policy (ie `CallApi(...)` in this case) itself is async, then the async variants of the policies should be used. — mountain traveller, Dec 17 '18 at 20:36

mountain traveller · Answer 1 · 2018-12-17T20:39:22.287

I want each call to Notify() to run on a new thread. So, my question is: [...] is that automatically run on a new thread by polly?

No. As the Polly bulkhead wiki page says:

The policy itself does not place calls onto threads; it assumes upstream systems have already placed calls into threads, but limits their parallelization of execution

There is no concept of task-scheduling (using a TaskScheduler) within Polly (except, for completeness, in the very specialised case of synchronous pessimistic TimeoutPolicy).

For completeness, however, all Polly policies are thread-safe.

Does Polly Bulkhead policy itself place calls onto threads?

1 Answers1