synchronization - Akka and two-way actor conversations -

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akka-based actor messaging feels one-way stream/flow of messages "upstream" actor 1 or more "downstream" actors.

but there might legitimate use case kind of two-way (request/response) synchronous messaging between 2 actors. instance, might have cacheactor manages cache. other actors might want put , get cache entries cache, , need through cacheactor:

// groovy pseudo-code class cacheactor extends untypedactor {     map<string,object> cache      // ...      @override     void onreceive(object message) {         if(message instanceof getcacheentry) {             getcacheentry getcacheentry = message getcacheentry             string entry = cache.get(getcacheentry.key)              // what? how send actor called this?!?             getcacheentry.sender.tell(new getcacheentryresult(getcacheentry.buzz, entry))   // <-- 2. return sender (again 'buzz' sidecar)         }     } }  class fizzactor extends untypedactor {     actorref cacheactor      @override     void onreceive(object message) {         if(message instanceof buzz) {             buzz buzz = message buzz             cacheactor.tell(new getcacheentry(buzz, this))  // <-- 1. identify 'this' sender , pass 'buzz' in sidecar         } else if(message instanceof getcacheentryresult) { // <-- 3. recognize processing result #1 above             getcacheentryresult result = message getcacheentryresult             buzz originalbuzz = result.buzz             string resultantentry = result.entry              // 4. keep processing...         }     } }

this way can envision passing messages , forth between 2 actors in "conversational" request-response style. problem bit nasty:

  • i have create new message types (e.g. getcacheentryresult) each response sent requester, bloat code; and
  • each time 1 actor responds another, of "context variables" "in scope" need bundled , sent requesting actor sidecars, available requester when receive answer , need continue processing (see buzz below). in more complicated orchestration between several actors, "context map" going big; and
  • at end of day, solution feels code smell me...

so ask: is there better way in akka? maybe using futures or ask(...) method?


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