I have a question about how to use the mutex In this documen

Question

I have a question about how to use the mutex In this document they use mutex like this In this way we can not prevent duplicating network requests How about wrapping whole the function Or do you have any other recommendations ``` suspend fun getLatestNews refresh Boolean = false List lt ArticleHeadline gt if refresh || latestNews isEmpty val networkResult = newsRemoteDataSource fetchLatestNews Thread safe write to latestNews latestNewsMutex withLock this latestNews = networkResult return latestNewsMutex withLock this latestNews ``` Source <https developer android com topic architecture data layer cache the result of the network request> ``` suspend fun getLatestNews refresh Boolean = false List lt ArticleHeadline gt return latestNewsMutex withLock if refresh || latestNews isEmpty val networkResult = newsRemoteDataSource fetchLatestNews this latestNews = networkResult this latestNews ```

takahirom · Answer

The tradeoff is that if a network request takes 10 seconds and then 5 seconds later you start executing a second request and the second request references a different cache key the block will take 20 seconds However I believe it is better to enclose the request in a mutex in the basic pattern

chanjungskim · Answer

What do you wanna achieve

takahirom · Answer

Currently what I would like to achieve is to eliminate duplicate requests

McEna · Answer

You can control it manually Like you said the mutex would affect non related requests

McEna · Answer

For example in my last position I had a network layer being called from separate processes So requests could be duplicated which had to be avoided but at the same time other request had to be sent without delay

McEna · Answer

So instead of mutex amp methods with return types I created asynchronous methods with a centralized collection of callbacks amp a collection of active requests With that every time you call the requests methods you can just ask are we already requesting this if so just add this extra callback to the pile Otherwise add the callback amp start the request

McEna · Answer

Now you could simplify your scenario by using an observable like Flow or LiveData That way instead of requesting data amp potentially duplicating network petitions your app just listens to updates from the data source At that point you can set up a delay to fire network requests amp refresh the data or manual triggers like a pull or both

McEna · Answer

Generally speaking most of the time you ll want I O to be fully asynchronous No matter what you use just don t wait for things to happen let them tell you when they happen

Jan · Answer

There are cases where your async operations rely on a single resource e g trading a refresh token There you need to make sure not multiple network requests recover simultaneously

Jan · Answer

In that case just make sure to not accidentally mix java threading and coroutines Synchronisation e g semaphores synchronized or reenteantlock Mutex seemed to work Just don t use the same mutex at different places to avoid deadlocks