如何在Akka http上设置file-io-dispatcher？

Question

When I was trying to start akka I had this error with ConfigFactory.load() :

Exception in thread "main" com.typesafe.config.ConfigException$UnresolvedSubstitution: reference.conf @ jar:file:/home/faoxis/.ivy2/cache/com.typesafe.akka/akka-http_2.12/jars/akka-http_2.12-10.1.5.jar!/reference.conf: 51: Could not resolve substitution to a value: ${akka.stream.blocking-io-dispatcher}

In source code I found this:

# Fully qualified config path which holds the dispatcher configuration
  # to be used by FlowMaterialiser when creating Actors for IO operations.
  file-io-dispatcher = ${akka.stream.blocking-io-dispatcher}

I have a question with it. Can I use some default setting without using environment variable akka.stream.blocking-io-dispatcher ? Maybe I can set up that by application.conf ?

Answer 1

The only thing you can do with application.conf and Environment Variables is override properties that are defined in reference.conf .

So you can configure akka.stream.blocking-io-dispatcher in any of them.

Strange is that usually there is a default value set. I use akka-http with Play and I never had to set any configuration.

See here the akka-streams Configuration: stream-configuration