Handle domain event handlers concurrently with exception isolation

[1owkeyme]

Summary by CodeRabbit

• New Features

  • Domain-event handlers now run concurrently, improving responsiveness and preventing one handler from blocking others.
  • Processing continues when an individual handler fails, with errors recorded for troubleshooting.

• Bug Fixes

  • Prevented deadlocks when event handlers wait on one another.
  • Ensured successful handlers continue producing follow-up events despite failures elsewhere.

• Chores

  • Updated the project version to 4.12.0.
  • Improved project metadata formatting and excluded editor configuration files from version control.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: f19549ee-e5f5-476d-abf3-4bc3551ad5c5

📥 Commits

Reviewing files that changed from the base of the PR and between 5a71d71 and 8052f56.

📒 Files selected for processing (5)

• .gitignore
• pyproject.toml
• src/cqrs/events/event_emitter.py
• tests/unit/test_event_emitter_handler_events.py
• tests/unit/test_event_fallback.py

Included review availability: Your plan includes up to 1 review per rolling hour; 0 remain after this review.

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📝 Walkthrough

Walkthrough

The event emitter now executes domain-event handlers concurrently, isolates handler failures, logs exceptions, and collects successful follow-up events. Tests cover concurrency and failure isolation. Project metadata formatting and version information were also updated.

Changes

Concurrent domain event dispatch

Layer / File(s)	Summary
Concurrent handler execution and validation src/cqrs/events/event_emitter.py, tests/unit/test_event_emitter_handler_events.py, tests/unit/test_event_fallback.py	Domain handlers run through asyncio.gather. Handler failures are logged independently, while successful follow-up events remain collected. Tests cover concurrent execution and continued processing after an exception.

Project metadata updates

Layer / File(s)	Summary
Project metadata and workspace configuration .gitignore, pyproject.toml	Added .vscode to ignored paths, reformatted metadata entries, and updated the project version from 4.11.0 to 4.12.0.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Merge Risk: ⚪ Minimal · up to 8052f

The change dispatches domain event handlers concurrently while isolating exceptions; no actionable merge-blocking risk remains, pending normal checks and review.

Sequence Diagram(s)

sequenceDiagram
  participant EventEmitter
  participant asyncio_gather
  participant DomainHandlers
  participant Logger
  EventEmitter->>asyncio_gather: schedule _process_single_handler calls
  asyncio_gather->>DomainHandlers: invoke handlers concurrently
  DomainHandlers-->>asyncio_gather: return follow-up events or exceptions
  asyncio_gather-->>EventEmitter: return handler results
  EventEmitter->>Logger: log handler exceptions with context
  EventEmitter-->>EventEmitter: collect successful follow-up events

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Suggested reviewers: vadikko2

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly summarizes the main change: concurrent domain event handlers with isolated exceptions.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch parallel-domain-events

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