concurrency | Java Concurrency Samples | Application Framework library

I have an app which deployment target is iOS 12.1, with many protocols defining functions with completion handlers, i.e.

when I run android application in real device I am getting following gradle errors

I just switched from ForkPool to gevent with concurrency (5) as the pool method for Celery workers running in Kubernetes pods. After the switch I've been getting a non recoverable erro in the worker:

amqp.exceptions.PreconditionFailed: (0, 0): (406) PRECONDITION_FAILED - delivery acknowledgement on channel 1 timed out. Timeout value used: 1800000 ms. This timeout value can be configured, see consumers doc guide to learn more

The broker logs gives basically the same message:

2021-11-01 22:26:17.251 [warning] <0.18574.1> Consumer None4 on channel 1 has timed out waiting for delivery acknowledgement. Timeout used: 1800000 ms. This timeout value can be configured, see consumers doc guide to learn more

I have the CELERY_ACK_LATE set up, but was not familiar with the necessity to set a timeout for the acknowledgement period. And that never happened before using processes. Tasks can be fairly long (60-120 seconds sometimes), but I can't find a specific setting to allow that.

I've read in another post in other forum a user who set the timeout on the broker configuration to a huge number (like 24 hours), and was also having the same problem, so that makes me think there may be something else related to the issue.

Any ideas or suggestions on how to make worker more resilient?

According to Java Concurrency in Action if we have the following class:

I would like to limit concurrency to one run for my workflow:

I want to handle Flux to limit concurrent HTTP requests made by List of Mono.

When some requests are done (received responses), then service requests another until the total count of waiting requests is 15.

A single request returns a list and triggers another request depending on the result.

At this point, I want to send requests with limited concurrency. Because consumer side, too many HTTP requests make an opposite server in trouble.

I used flatMapMany like below.

I am having a lot of issues handling concurrent runs of a StateMachine (Step Function) that does have a GlueJob task in it.

The state machine is initiated by a Lambda that gets trigger by a FIFO SQS queue.

The lambda gets the message, checks how many of state machine instances are running and if this number is below the GlueJob concurrent runs threshold, it starts the State Machine.

The problem I am having is that this check fails most of the time. The state machine starts although there is not enough concurrency available for my GlueJob. Obviously, the message the SQS queue passes to lambda gets processed, so if the state machine fails for this reason, that message is gone forever (unless I catch the exception and send back a new message to the queue).

I believe this behavior is due to the speed messages gets processed by my lambda (although it's a FIFO queue, so 1 message at a time), and the fact that my checker cannot keep up.

I have implemented some time.sleep() here and there to see if things get better, but no substantial improvement.

I would like to ask you if you have ever had issues like this one and how you got them programmatically solved.

Thanks in advance!

This is my checker:

I would like to extend AsyncSequence in ways that depend on whether the sequence can throw. Neither AsyncSequence nor AsyncIteratorProtocol distinguish such sequences explicitly. Yet, the concurrency module does come with concrete sequences with throwing and non-throwing variants. The only generic difference I see is that the next method of non-throwing sequences are rethrowing. Here is an example:

In WWDC 2021 video, Protect mutable state with Swift actors, they provide the following code snippet: