Hi,

I've got an application that uses akka. One bit of it listens to stdin and
on a newline terminates an actor. This has a knock-on effect of closing
down the entire system. The line is the return value of a future, and is:

io.Source.*stdin*.getLines().take(1).foreach(_ => minion ! StopMinioning)


The execution context here is the one provided by the Akka system. The
problem is that this future sits in a blocking state even after the akka
system (and presumably associated thread pools) have shut down. It gets
stuck here:

"MySystem-akka.actor.default-dispatcher-6" #16 prio=5 os_prio=0
tid=0x00007f81c0004000 nid=0x536b runnable [0x00007f821b9fb000]
   java.lang.Thread.State: RUNNABLE
at java.io.FileInputStream.readBytes(Native Method)
at java.io.FileInputStream.read(FileInputStream.java:234)
at java.io.BufferedInputStream.read1(BufferedInputStream.java:284)
at java.io.BufferedInputStream.read(BufferedInputStream.java:345)
- locked <0x0000000706a1b560> (a java.io.BufferedInputStream)
at sun.nio.cs.StreamDecoder.readBytes(StreamDecoder.java:284)
at sun.nio.cs.StreamDecoder.implRead(StreamDecoder.java:326)
at sun.nio.cs.StreamDecoder.read(StreamDecoder.java:178)
- locked <0x0000000706a1c610> (a java.io.InputStreamReader)
at java.io.InputStreamReader.read(InputStreamReader.java:184)
at java.io.BufferedReader.fill(BufferedReader.java:161)
at java.io.BufferedReader.readLine(BufferedReader.java:324)
- locked <0x0000000706a1c610> (a java.io.InputStreamReader)
at java.io.BufferedReader.readLine(BufferedReader.java:389)
at
scala.io.BufferedSource$BufferedLineIterator.hasNext(BufferedSource.scala:67)
at scala.collection.Iterator$$anon$10.hasNext(Iterator.scala:308)
at scala.collection.Iterator$class.foreach(Iterator.scala:727)
at scala.collection.AbstractIterator.foreach(Iterator.scala:1157)

It looks like whatever job system.shutdown does, it doesn't do enough to
notify this IO-blocked thread. system.awaitTermination() is returning so
akka thinks it has shut down.

Is there a way to address this? I really need to be able to both read lines
from stdin and also guarantee that the system shuts down gracefully. It may
be running in a managed environment were I can't leak threads and can't
call System.exit().

Thanks,
Matthew

-- 
Dr Matthew Pocock
Turing ate my hamster LTD
mailto: [email protected]

Integrative Bioinformatics Group, School of Computing Science, Newcastle
University
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