Issues with Future ? #124
Comments
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Thanks for reporting! I'm able to reproduce. Interestingly, the same happens in the Scala REPL $ scala
Welcome to Scala 2.12.7 (Java HotSpot(TM) 64-Bit Server VM, Java 1.8.0_192).
Type in expressions for evaluation. Or try :help.
scala> import scala.concurrent._, duration._, ExecutionContext.Implicits.global
import scala.concurrent._
import duration._
import ExecutionContext.Implicits.global
scala> Await.result(Future(1), 500.millis)
java.lang.NoClassDefFoundError: Could not initialize class $line10.$read$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$
at scala.runtime.java8.JFunction0$mcI$sp.apply(JFunction0$mcI$sp.java:12)
at scala.concurrent.Future$.$anonfun$apply$1(Future.scala:654)
at scala.util.Success.$anonfun$map$1(Try.scala:251)
at scala.util.Success.map(Try.scala:209)
at scala.concurrent.Future.$anonfun$map$1(Future.scala:288)
at scala.concurrent.impl.Promise.liftedTree1$1(Promise.scala:29)
at scala.concurrent.impl.Promise.$anonfun$transform$1(Promise.scala:29)
at scala.concurrent.impl.CallbackRunnable.run(Promise.scala:60)
at java.util.concurrent.ForkJoinTask$RunnableExecuteAction.exec(ForkJoinTask.java:1402)
at java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:289)
at java.util.concurrent.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1056)
at java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1692)
at java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:157)
java.util.concurrent.TimeoutException: Futures timed out after [500 milliseconds]
at scala.concurrent.impl.Promise$DefaultPromise.ready(Promise.scala:255)
at scala.concurrent.impl.Promise$DefaultPromise.result(Promise.scala:259)
at scala.concurrent.Await$.$anonfun$result$1(package.scala:215)
at scala.concurrent.BlockContext$DefaultBlockContext$.blockOn(BlockContext.scala:53)
at scala.concurrent.Await$.result(package.scala:142)
... 28 elidedThe same happens in the Ammonite REPL, but I can't reproduce with tut 🤔 |
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It’s really odd that it happens at all, isn’t it? Is there something dodgy with the default execution context? |
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Something is going on with val members of objects that access any execution context scala> import scala.concurrent._, duration._
import scala.concurrent._
import duration._
scala> import java.util.concurrent.Executors
import java.util.concurrent.Executors
scala> implicit val ec = ExecutionContext.fromExecutor(Executors.newCachedThreadPool())
ec: scala.concurrent.ExecutionContextExecutor = scala.concurrent.impl.ExecutionContextImpl@5f36c8e3
scala> Await.result(Future(1), 500.millis)
Exception in thread "pool-1-thread-1" java.lang.NoClassDefFoundError: Could not initialize class $line15.$read$$iw$$iw$$iw$$iw$$iw$$iw$
at scala.runtime.java8.JFunction0$mcI$sp.apply(JFunction0$mcI$sp.java:12)
at scala.concurrent.Future$.$anonfun$apply$1(Future.scala:654)
at scala.util.Success.$anonfun$map$1(Try.scala:251)
at scala.util.Success.map(Try.scala:209)
at scala.concurrent.Future.$anonfun$map$1(Future.scala:288)
at scala.concurrent.impl.Promise.liftedTree1$1(Promise.scala:29)
at scala.concurrent.impl.Promise.$anonfun$transform$1(Promise.scala:29)
at scala.concurrent.impl.CallbackRunnable.run(Promise.scala:60)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)
java.util.concurrent.TimeoutException: Futures timed out after [500 milliseconds]
at scala.concurrent.impl.Promise$DefaultPromise.ready(Promise.scala:255)
at scala.concurrent.impl.Promise$DefaultPromise.result(Promise.scala:259)
at scala.concurrent.Await$.$anonfun$result$1(package.scala:215)
at scala.concurrent.BlockContext$DefaultBlockContext$.blockOn(BlockContext.scala:53)
at scala.concurrent.Await$.result(package.scala:142)
... 28 elided
It seems the execution context does not work from a static initializer.. |
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It works fine if you wrap the call in a def or lazy val first scala> def x =Await.result(Future(1), 500.millis)
x: Int
scala> x
res2: Int = 1
scala> lazy val x= Await.result(Future(1), 500.millis)
x: Int = <lazy>
scala> x
res5: Int = 1These workarounds don't work in mdoc however, I suspect because in the REPL those become separate objects. Something fishy is going on, but I'm sure we can figure it out with more experimentation. I tried changing how we trigger the object constructor but that didn't help. |
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I'm able to reproduce this error with tut now cat in/in.md
```tut
import scala.concurrent._
import scala.concurrent.duration._
import ExecutionContext.Implicits.global
Await.result(Future(1), 500.millis)
```
➜ target git:(future) ✗ coursier launch -r "https://dl.bintray.com/tpolecat/maven/" org.tpolecat:tut-core_2.12:0.6.10 -- \
in out '.*\.md$' -classpath $(coursier fetch -p org.scala-lang:scala-library:2.12.8)
[tut] compiling: in/in.md
java.lang.NoClassDefFoundError: Could not initialize class $line7.$read$$iw$$iw$$iw$$iw$$iw$$iw$
at scala.runtime.java8.JFunction0$mcI$sp.apply(JFunction0$mcI$sp.java:12)
at scala.concurrent.Future$.$anonfun$apply$1(Future.scala:654)
at scala.util.Success.$anonfun$map$1(Try.scala:251)
at scala.util.Success.map(Try.scala:209)
5 ```tut
at scala.concurrent.Future.$anonfun$map$1(Future.scala:288)
at scala.concurrent.impl.Promise.liftedTree1$1(Promise.scala:29)
at scala.concurrent.impl.Promise.$anonfun$transform$1(Promise.scala:29)
at scala.concurrent.impl.CallbackRunnable.run(Promise.scala:60)
at java.util.concurrent.ForkJoinTask$RunnableExecuteAction.exec(ForkJoinTask.java:1402)
at java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:289)
at java.util.concurrent.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1056)
at java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1692)
at java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:157)
[tut] *** Error reported at /Users/olafurpg/dev/mdoc/target/in/in.md:5
java.util.concurrent.TimeoutException: Futures timed out after [500 milliseconds]The problem seems related to starting the future and awaiting on it in the same object constructor. For example, The following program runs OK object a {
val x = Future(1)
}
object b {
println(Await.result(a.x, Duration("500ms")))
}while this program here doesn't object a {
val x = Await.result(Future(1), Duration("500ms")
}
object b {
println(a.x)
} |
olafurpg
added a commit
that referenced
this issue
Jan 1, 2019
Fixes #124 - enable -Ydelamdafy:inline by default to avoid future timeouts - handle exceptions with null messages by delegating to cause if any, or falling back to the message "null". - trim stacktrace of all exceptions, also causes. - catch initialization exceptions in addition to `NonFatal`, since they happen when vals in mdoc code fences crash.
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-Ydelambdafy:inline fixes the problem, opened #126 enabling it by default and improving error handling of exceptions so that multi-cause stack traces are more readable. The timeout error is a Scala 2.12 bug scala/bug#9824 |
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Given the two following blocks:
And
I would expect the
Futureto complete.This is what happens in 1.0.0, but 1.1.0 spits out the following stack trace:
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