Best way to limit the number of active Tasks running via the Parallel Task Library

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I just gave an answer which is very applicable to this question.

Basically, the TPL Task class is made to schedule CPU-bound work. It is not made for blocking work.

You are working with a resource that is not CPU: waiting for service replies. This means the TPL will mismange your resource because it assumes CPU boundedness to a certain degree.

Manage the resources yourself: Start a fixed number of threads or LongRunning tasks (which is basically the same). Decide on the number of threads empirically.

You can’t put unreliable systems into production. For that reason, I recommend #1 but throttled. Don’t create as many threads as there are work items. Create as many threads which are needed to saturate the remote service. Write yourself a helper function which spawns N threads and uses them to process M work items. You get totally predictable and reliable results that way.

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