how does scope works in this gist

Question

how does scope works in this gist <https gist github com thiyagu06 549b03512818eac42c123c4bd0456003 file producerconsumer kt L45> Both `producerContext` and `consumerContext` will have same `CoroutineScope` does `flowScope cancel ` make both coroutines context not to accept any more task in it

tseisel · Answer

`producerContext` and `consumerContext` are 2 independent contexts one is backed by one thread the other has a pool of 2 threads When collecting from the flow the code from `channelFlow` will be executed on the producer thread and each element is notified on one of the consumer threads Cancelling the `flowScope` results in 1 Cancelling the consumer coroutine the one started by `launchIn` 2 Cancel collection of the flow and therefore the block in `awaitClose` it called on the producer thread

Thiyagu · Answer

Thanks for the explanation I understand that `flowScope cancel ` is enough stop the flow and both coroutineContext will be stopped both my context will be having the same scope

tseisel · Answer

Some vocabulary here A `Job` is an unit of work that has a lifecycle started stopped cancelled A `CoroutineDispatcher` describes how coroutines are executed and resumed It abstracts threads away A `CoroutineContext` is the sum of multiple properties `Job`s and `CoroutineDispatcher`s may be part of a `CoroutineContext` A `CoroutineScope` is the primitive for structured concurrency It simply wraps a `CoroutineContext` and cancelling a scope indirectly cancels jobs that are part of its context From those definitions we deduce that being based on `CoroutineDispatcher`s both `producerContext` and `consumerContext` will not stop their thread pool will still be allocated Because the producer coroutine in `channelFlow` is launched in the scope of its `ProducerScope` it is automatically cancelled when the flow collection is cancelled you don t need to manually cancel the job in `awaitClose`

tseisel · Answer

Then yes cancellation of the coroutine that called `collect` or `launchIn` in this case will cancel any upstream operations including the producer

tseisel · Answer

Note you can simplify the `channelFlow` block by replacing it with the following ```flow while true emit Random nextInt 1000 delay 100 buffer ```

Thiyagu · Answer

Hey again thanks for the nice explanation of each concept I update the gist based on your inputs <https gist github com thiyagu06 549b03512818eac42c123c4bd0456003> The reason i m using using channelFlow is I will replace the random number generation with http request

Thiyagu · Answer

Basically I tried to achieve the below things This will be independent JVM process which will run in background When I stop the background thread all coroutines must stopped properly 1 poll indefinitely http endpoint and get the data in batches say 10 per batch 2 do some async process and store it in DB 3 acknowledge that received data is processed successfully call http endpoint