kotlinlang #coroutines

is there a way to improve the intellij debugger experience with coroutines? More often then not i'm facing the problem, that once an exception was thrown executing a coroutine containing a breakpoint, it wont be hit ever again from that point although it is executed

svenjacobs

08/28/2019, 1:25 PM

One more question: Trying to replace

Channel

with

Flow

for my API requests. Using Firebase Firestore here and want to listen for document updates. As of now I create a

Channel

, then on the Firestore

Query

I call `addSnapshotListener()`and inside the listener I call

channel.offer()

when there are snapshots incoming. Also I call

channel.invokeOnClose { registration.remove() }

where

registration

is the

ListenerRegistration

returned by

addSnapshotListener

. How do I perform the last step with

Flow

, ensuring that no listeners are leaked?

myanmarking

08/28/2019, 2:13 PM

Copy code

fun onViewAttached(textChanged: Flow<String>) {
        mainScope.launch {
            textChanged
                    .onStart { emit("") }
                    .debounce(700)
                    .flatMapLatest { pagedListManager.buildDataSource(it) }
                    .collect {
                        postEvent(TvShowViewStates.ShowTvShow(it))
                    }
        }
    }

myanmarking

08/28/2019, 2:13 PM

is there a way to skip debounce for the first emission ?

myanmarking

08/28/2019, 2:25 PM

hacked a solution like this

myanmarking

08/28/2019, 2:25 PM

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public fun <T> Flow<T>.debounce(skipFirst: Boolean, timeoutMillis: Long): Flow<T> {
    var isFirst = true

    return flow {
        if (skipFirst && isFirst) {
            isFirst = false
            collect { emit(it) }
        } else {
            map { debounce(timeoutMillis) }
        }
    }
}

Joost de Vries

08/29/2019, 5:44 AM

I like the warning

Inappropriate blocking method call

when somebody accidentally calls blocking from a suspend function. Is it possible to get that warning in gradle as well? Or is there another way to have CI build fail when this happens?

roy

08/30/2019, 7:49 AM

A conflated broadcast channel only returns the last line so it's not really useable for that

Yasir Ali

08/30/2019, 9:37 AM

Question: How to cancel a running LiveData Coroutine Block? https://stackoverflow.com/questions/57723714/how-to-cancel-a-running-livedata-coroutine-block

asad.awadia

08/30/2019, 9:35 PM

I know it’s trying to be quite similar to rxjava

🧵 2

asad.awadia

08/30/2019, 9:36 PM

Personal opinion: rx java was the most weirdly used library - it was made for observables and streams of values but devs used it mainly to move things across threads

🧵 1

thana

09/02/2019, 7:51 AM

does anyone have experience with micrometer an coroutines? Will it "simply work" if i put a

@Timed

annotation on a

suspend fun

thana

09/02/2019, 9:56 AM

if i understand https://github.com/Kotlin/kotlinx.coroutines/blob/master/integration/kotlinx-coroutines-slf4j/src/MDCContext.kt correctly, i put the

MDCContext

into the coroutine context once and can read the values from any child context, but only if i modify the

MDC

i have to recteate the

MDCContext

, right?

synhershko

09/03/2019, 7:27 AM

I have a BroadcastChannel (

bc

) with multiple consumers, each process the messages from

bc

and sends messsages to another “sink” channel

. The “sink” channel is defined as

val t = Channel<Tag>(Channel.UNLIMITED)

and I can consistently reproduce a situation where messages are sent to it but the consumer of

never sees them. If I change t’s definition to

val t = Channel<Tag>()

- meaning changing from UNLIMITED to RENDEZVOUS - all works as expected (no messages are dropped). Any idea what’s going on?

David Glasser

09/08/2019, 7:14 PM

FYI: we are starting to experiment with rolling out Kotlin coroutines for a project. We turned on kotlinx.coroutines.debug because we read some docs saying the performance impact is negligable. We also deploy with the YourKit profiler debug agent. We were seeing some odd performance issues (like, to the degree of k8s killing our servers due to liveness check failures), so we configure to get a stack trace when we get killed. Every thread that had any code written by us running in it ended with something like

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"epollEventLoopGroup-4-3 @call-handler#1379475" #50 prio=10 os_prio=0 tid=0x00007fbe1c05fec0 nid=0x42 runnable [0x00007fbe22efb000]
   java.lang.Thread.State: RUNNABLE
	at com.yourkit.runtime.Callback.setEventTableStringColumn(Native Method)
	at com.yourkit.runtime.CallbackProxyImpl.setEventTableStringColumn(CallbackProxyImpl.java:197)
	at com.yourkit.probes.StringColumn.setValue(StringColumn.java:17)
	at com.yourkit.probes.ResourceTable.setResourceName(ResourceTable.java:70)
	at com.yourkit.probes.builtin.Threads$Thread_setName_Probe.onReturn(Threads.java:199)
	at java.lang.Thread.setName(Thread.java:1133)
	- locked <0x00000006827db478> (a io.netty.util.concurrent.FastThreadLocalThread)
	at kotlinx.coroutines.CoroutineId.restoreThreadContext(CoroutineContext.kt:83)
	at kotlinx.coroutines.CoroutineId.restoreThreadContext(CoroutineContext.kt:60)
	at kotlinx.coroutines.internal.ThreadContextKt.restoreThreadContext(ThreadContext.kt:95)
	at kotlinx.coroutines.intrinsics.UndispatchedKt.startCoroutineUndispatched(Undispatched.kt:200)
	at kotlinx.coroutines.CoroutineStart.invoke(CoroutineStart.kt:111)
	at kotlinx.coroutines.AbstractCoroutine.start(AbstractCoroutine.kt:154)
	at kotlinx.coroutines.future.FutureKt.future(Future.kt:44)
	at kotlinx.coroutines.future.FutureKt.future$default(Future.kt:36)

So we're certainly not positive but it sure seems like kotlinx.coroutines.debug has non-negligable performance impact when combined with YourKit.

Paul Woitaschek

09/09/2019, 10:12 AM

@ansman How did you actually fix this? Having this with android plugin 3.6.0-alpha10 & coroutines 1.3.1 right now

Dico

09/09/2019, 3:55 PM

Should I launch a new coroutine on GlobalScope to do the task?

sdeleuze

09/10/2019, 1:34 PM

https://kotlinlang.slack.com/archives/C0BJ0GTE2/p1568122460069200

🙌 6

⏸️ 8

rocketraman

09/10/2019, 4:41 PM

Furthermore, the behavior of certain suspend functions e.g. Ktor client calls is different still -- in this case the exception stack reported is the ktor internal exception and doesn't even have the resume point in it.

rocketraman

09/10/2019, 6:03 PM

Aha: https://github.com/Kotlin/kotlinx.coroutines/commit/675c30c4b96533a374ae36b144dbe6b26634b97b#diff-c7f3d4f9ce627923c7ad3829905b68fcR27 -- so stacktrace recovery is not enabled by default. Is there any plan to do so in the future?

Sergio C.

09/10/2019, 7:39 PM

awesome...

vngantk

09/11/2019, 9:03 AM

I have logged an issue in Github to see what the Kotlin team would respond to my interpretation: https://github.com/Kotlin/kotlinx.coroutines/issues/1527

Stanislav Shamilov

09/12/2019, 9:51 PM

Hi all. In the following code channel variable in the statement this.channel.offer(it ?: “”) is highlighted with a warning “Non-applicable call for builder inference”.

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fun EditText.textChanges(): Flow<String> = callbackFlow {
    val textWatcher = textWatcher(afterText = {
        this.channel.offer(it ?: "")
    })
    this@textChanges.addTextChangedListener(textWatcher)
    awaitClose { this@textChanges.removeTextChangedListener(textWatcher) }
}

private fun textWatcher(
    beforeText: (String?) -> Unit = {},
    onText: (String?) -> Unit = {},
    afterText: (String?) -> Unit = {}
): TextWatcher {
    return object : TextWatcher {
        override fun afterTextChanged(s: Editable?) = afterText(s?.toString())
        override fun beforeTextChanged(s: CharSequence?, start: Int, count: Int, after: Int) = beforeText(s?.toString())
        override fun onTextChanged(s: CharSequence?, start: Int, before: Int, count: Int) = onText(s?.toString())
    }
}

Kotlin version: 1.3.50 Coroutines version: 1.3.0 IDE: Android Studio 3.5 I have two questions: 1. Why does this warning show up? 2. What does this warning stand for? Thanks in advance!

myanmarking

09/13/2019, 12:45 PM

anyway to make the test work with

Copy code

advanceTimeBy

louiscad

09/14/2019, 5:15 PM

Yes, using

Call<Void?>

(without suspend modifier) with the

await

suspending extension.