Ensure that all raced promises are resolved after the race

[milindl]

Each race spawns a new promise for every promise being raced, and long-lived promises can cause an issue with that.For each promise being raced, it's safe to resolve it immediately after the race if we can guarantee that no one else is waiting on it.There are 3 places of significance when it comes to racing:

1. checkMaxPollIntervalNotExceeded which races #maxPollIntervalRestart with a timer. This method can only be called on the non-worker async context (ie. only one instance of this method is running). Further, when the promise is being raced here, the same promise is not being raced in any other method (This can be checked by checking the other sites which might await #maxPollIntervalRestart . Only other site is cacheExpirationLoop and these two methods are never called together, as one calls the other.
2. cacheExpirationLoop : this is racing both #maxPollIntervalRestart and #workerTerminationScheduled. The first one can be resolved safely with the same logic as (1). For #workerTerminationScheduled we can actually remove it from the race. Why? Because #workerTerminationScheduled resolved means that very soon #maxPollIntervalRestart will be resolved too (in the main runInternal loop). Otherwise the timer will expire but then the while loop will check the expiry of #workerTerminationScheduled .
3. The last one, .#queueNonEmpty is the trickiest because all workers can be awaiting it at the same time, so resolving it unconditionally causes a case where workers wake each other up without anything actually being in the queue. I thought maybe, rather than removing the promise, I will remove the race, and await only the promise. Unfortunately, this makes some workers halt: the fetcher returning messages as null, and the call to nextFetchRetry can be interrupted by queueNonEmptyCb in the middle of them. I thought of a possible way to solve the race condition, but I think my proposed solution is better: to maintain a linked list of waiters. Linked list size is bounded by worker count.

This addresses #150

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[emasab]

Thanks for the fix Milind! Just a few comments

[emasab]

LGTM!

[AndreasKlein]

Hi @milindl is there a plan for when this will be released already?