akka/akka-core

Unstashed messages enqueued in TestActorRef mailbox while processing a message from self are stuck until another message is received

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#30,170 opened on Apr 7, 2021

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 (1 comment) (0 reactions) (0 assignees)Scala (13,277 stars) (3,547 forks)batch import
help wantednice-to-have (low-prio)t:testing

Description

In the following workflow, unstashed messages are enqueued in the mailbox but are not processed as expected:

  1. Send message (messageOne) from TestKit to TestActorRef
  2. TestActorRef underlying actor stashes messageOne and schedules a subsequent message to self (selfMessage)
  3. selfMessage is sent and processed and messageOne is unstashed during processing of selfMessage
  4. messageOne is not processed
  5. Send another message (messageTwo) from TestKit to TestActorRef
  6. Both messageOne and messageTwo are processed

akka.testkit.CallingThreadDispatcher#runQueue appears to process the provided MessageQueue at the time of invocation rather than using the active Mailbox MessageQueue.

Contributor guide

Tech stack
scala
Domain
backendtesting
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
4
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
3-5 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
mostly clear
Prerequisites
Akka fundamentalsUnderstanding of actor mailboxKnowledge of CallingThreadDispatcher
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
20
Research direction
Investigate the implementation of CallingThreadDispatcher.runQueue method and its interaction with the Mailbox's MessageQueue. The issue suggests that runQueue processes the provided MessageQueue instead of the active one. Compare with the expected behavior and check if there are any related changes in the codebase. Consider looking at the stashing mechanism and how messages are unstashed during self message processing.