Hi ```fun OkhttpAuthenticator authenticate synchronized this

Question

Hi ```fun OkhttpAuthenticator authenticate synchronized this runBlocking retrofitService suspendingRefreshTokens lt ``` Could this get broken somehow runBlocking seems to swap to caller thread context after the network call so the mutex should be released or is it not guaranteed Because I see certain bugs in production where the code just stops and not sure if its runBlocning or retrofit related

bezrukov · Answer

if `OkhttpAuthenticator authenticate ` is invoked in okhttp s Interceptor Authenticator and `retrofitService` uses the same okhttpclient it might be related to okhttp s Dispatcher see maxRequests maxRequestsPerHost

bezrukov · Answer

if it is the case it s happening because all okhttp calls are invoked in okhttp Dispatcher s executor with concurrency 5 by default Imagine you re started 5 queries and all of them require token refresh When using runBlocking suspendingRetrofitCall it will schedule this call to the same executor and deadlock happens because your 5 calls are waiting for token refresh and token refresh call is waiting for these calls

ursus · Answer

alright so the issue is that the retrofit call wants to switch threads if I made it synchronous and on caller thread it should be okay right

ursus · Answer

which would explain why it didnt manifest in rxjava because there I didnt use the async parameter which makes it use okhttp pool and kept it on caller thread

bezrukov · Answer

gt if I made it synchronous and on caller thread it should be okay right yep should be ok blocking calls bypass okhttp executor Another option is to setup retrofit service for token refresh with dedicated okhttp dispatcher

ursus · Answer

you mean to drive Retrofit with a swapped out okhttp with a custom unbounded thread pool impl explicity for network calls made inside interceptors authenticator

bezrukov · Answer

no just use `yourOkHttpClient newBuilder dispatcher Dispatcher ` when building your retrofitService service

bezrukov · Answer

in this case regular requests and requests for token refresh will be executed in different executors

ursus · Answer

yes thats what I meant

ursus · Answer

thanks for you help

ursus · Answer

If I might add the issue is not necessarily the synchronization block right even without it if the threadpool is maxed out and I want a new max+1 request within the authenticator it will stall right

bezrukov · Answer

yep

ursus · Answer

Also giving auth layer its own threadpool dispatcher possibly wasteful no doubling the threads or is it negligible I d best have it run on caller thread and still using the suspend api in retrofit to have cancelation or coroutines <http dispatcher io|dispatcher io>

bezrukov · Answer

actually you do not double the threads because okhtttp creates executor with the following arguments ```ThreadPoolExecutor 0 Int MAX VALUE 60 TimeUnit SECONDS ``` that means this pool will create threads lazily and will keep it only for 60 seconds once they unused so I would say it s negligible Yep best option would be to call it synchronously on caller thread

ursus · Answer

Do you know if its possible to have it on caller thread amp keep suspend api i e the async parameter from former rxjava adapter

bezrukov · Answer

No suspend adapters generated differently so I think you need to just create sync adapter

ursus · Answer

Yea whats annoying the I have retrofit AuthApi where now login is suspending nad refreshTokens and logout is synchronous not great design