concurrency - Scala ProcessLogger & Future: How can I make sure all line callbacks are called BEFORE the onComplete block? -

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import scala.sys.process._ import scala.concurrent._ // (future) import executioncontext.implicits.global // (future)  /* run "ls /opt"  * outputs 2 lines:  *  - "x11"  *  - "local"  */ val command = process(seq("ls", "/opt"), none, "lang" -> "")  val process = command.run(processlogger(line => {   thread.sleep(1000) // slow execution down   println(thread.currentthread)   println(line)   println("") }))  future {   process.exitvalue // blocks until process exits }.oncomplete { results =>   println(thread.currentthread)   println("process exited: after last line callback finished?")   println("done") }

output (order as expected, case?):

thread[thread-47,5,run-main-group-0] line x11  thread[thread-47,5,run-main-group-0] line local  thread[forkjoinpool-1-worker-3,5,run-main-group-0] process exited: after last line callback finished? done

it seems o.k. because oncomplete block outputs text after line-related output over. case? makes sure different threads run 1 after other? can rely on supposed order?

a future object holding value may become available @ point. value result of other computation:

  1. if computation has not yet completed, future not completed.
  2. if computation has completed value or exception, future completed.

completion can take 1 of 2 forms:

  1. when future completed value, future completed value.

  2. when future completed exception thrown computation, future failed exception.

the simplest way create future object invoke future method starts asynchronous computation , returns future holding result of computation. result becomes available once future completes.

note future[t] type denotes future objects, whereas future method creates , schedules asynchronous computation, , returns future object completed result of computation.

doc

you can see more implementation details @ github


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