How to configure a fine tuned thread pool for futures?

This answer is from monkjack, a comment from the accepted answer. However, one can miss this great answer so I'm reposting it here.

implicit val ec = ExecutionContext.fromExecutor(Executors.newFixedThreadPool(10))

If you just need to change the thread pool count, just use the global executor and pass the following system properties.

-Dscala.concurrent.context.numThreads=8 -Dscala.concurrent.context.maxThreads=8

You can specify your own ExecutionContext that your futures will run in, instead of importing the global implicit ExecutionContext.

import java.util.concurrent.Executors
import scala.concurrent._

implicit val ec = new ExecutionContext {
    val threadPool = Executors.newFixedThreadPool(1000)

    def execute(runnable: Runnable) {
        threadPool.submit(runnable)
    }

    def reportFailure(t: Throwable) {}
}