lahja 0.11.0a1

Generic event bus for inter process asyncio communication

# Lahja

[](http://lahja.readthedocs.io/en/latest/?badge=latest)

[Documentation hosted by ReadTheDocs](http://lahja.readthedocs.io/en/latest/)

DISCLAIMER: This is alpha state software. Expect bugs.

Lahja is a generic multi process event bus implementation written in Python 3.6+ to enable lightweight inter-process communication, based on non-blocking asyncio.

## What is this for?

Lahja is tailored around one primary use case: enabling multi process Python applications to communicate through events between processes in a non-blocking asyncio fashion.

Key facts:

• non-blocking APIs based on asyncio

• lightweight and simple (e.g no IPC pipes etc)

• easy multicasting of events (one event, many independent receivers)

• easy event routing (e.g route event X only to process group Y)

• multiple consuming APIs to adapt to different use cases and styles

## TODOs

• Filter support (e.g. only subscribe to EventX from origin y)

• Push boundaries (don’t push this into process x)

• Testing

• Performance analysis

## Developer Setup

If you would like to hack on lahja, please check out the [Ethereum Development Tactical Manual](https://github.com/pipermerriam/ethereum-dev-tactical-manual) for information on how we do:

• Testing

• Pull Requests

• Code Style

• Documentation

### Development Environment Setup

You can set up your dev environment with:

`sh git clone https://github.com/cburgdorf/lahja cd lahja virtualenv -p python3 venv . venv/bin/activate pip install -e .[dev] `

### Testing Setup

During development, you might like to have tests run on every file save.

Show flake8 errors on file change:

`sh # Test flake8 when-changed -v -s -r -1 lahja/ tests/ -c "clear; flake8 lahja tests && echo 'flake8 success' || echo 'error'" `

Run multi-process tests in one command, but without color:

`sh # in the project root: pytest --numprocesses=4 --looponfail --maxfail=1 # the same thing, succinctly: pytest -n 4 -f --maxfail=1 `

Run in one thread, with color and desktop notifications:

`sh cd venv ptw --onfail "notify-send -t 5000 'Test failure ⚠⚠⚠⚠⚠' 'python 3 test on lahja failed'" ../tests ../lahja `

### Release setup

For Debian-like systems: ` apt install pandoc `

To release a new version:

`sh make release bump=$$VERSION_PART_TO_BUMP$$ `

#### How to bumpversion

The version format for this repo is {major}.{minor}.{patch} for stable, and {major}.{minor}.{patch}-{stage}.{devnum} for unstable (stage can be alpha or beta).

To issue the next version in line, specify which part to bump, like make release bump=minor or make release bump=devnum.

If you are in a beta version, make release bump=stage will switch to a stable.

To issue an unstable version when the current version is stable, specify the new version explicitly, like make release bump=”–new-version 4.0.0-alpha.1 devnum”