Difference between forward and tell in akka actors

scala akka actor
Michał Jurczuk picture Michał Jurczuk · Aug 4, 2014 · Viewed 16.1k times · Source

What is a difference between tell and forward, in case I will send the same message:

case msg: Message =>
  otherActor tell (msg,sender)

and

case msg: Message =>
  otherActor forward msg

Answer

Konrad 'ktoso' Malawski picture Konrad 'ktoso' Malawski · Aug 4, 2014

The sender() will be different on the receiving end.


Message sends using tell (also known as !):

A tells message M to B.
B tells that message to C.
C thinks the sender() of message M is B.


Message sends using forward:

A tells message M to B.
B forwards that message to C.
C thinks the sender() of message M is A.



Worth pointing out is, that you can achieve the same as forward when explicitly setting the sender of a message using tell, however this is not typical Akka-style:

// inside `B`, when received `msg` from `A`
C tell (msg, A) 
      == 
C forward msg



For more info refer to the docs about forward.

Related questions

When to use actors instead of messaging solutions such as WebSphere MQ or Tibco Rendezvous?

I've already read the question and answers to What design decisions would favour Scala's Actors instead of JMS?. Usually, we use messaging solutions which have existed for years already: either a JMS implementation such as WebSphere MQ or Apache ActiveMQ …

Read More
Akka in Scala, exclamation mark and question mark

What is the difference between exclamation mark (!) and question mark (?) when sending messages to Actors? myActor ! Hello(value1) myActor ? Hello(value1)

Read More
What's the difference of the Akka's Actor with Scala's Actor model

I found there is also an Akka actor model, so I am wondering what's the difference between the Akka's Actor and Scala's Actor model?

Read More