https://github.com/elixir-toniq/schism

Partition testing tool for elixir
https://github.com/elixir-toniq/schism

distributed-systems elixir erlang testing

Last synced: 6 months ago
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Partition testing tool for elixir

• Host: GitHub
• URL: https://github.com/elixir-toniq/schism
• Owner: elixir-toniq
• License: mit
• Created: 2019-02-17T15:23:06.000Z (over 7 years ago)
• Default Branch: master
• Last Pushed: 2023-03-30T11:01:18.000Z (about 3 years ago)
• Last Synced: 2025-06-30T19:53:53.751Z (12 months ago)
• Topics: distributed-systems, elixir, erlang, testing
• Language: Elixir
• Homepage:
• Size: 62.5 KB
• Stars: 71
• Watchers: 5
• Forks: 1
• Open Issues: 3
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

          
# Schism

[![CircleCI](https://circleci.com/gh/keathley/schism.svg?style=svg)](https://circleci.com/gh/keathley/schism)[![Documentation](https://img.shields.io/badge/docs-latest-blue.svg)](https://hexdocs.pm/schism/)

Schism provides a simple api for testing partitions between BEAM nodes.

Documentation: [https://hexdocs.pm/schism](https://hexdocs.pm/schism).

## Installation

If [available in Hex](https://hex.pm/docs/publish), the package can be installed

by adding `schism` to your list of dependencies in `mix.exs`:

```elixir

def deps do

  [

    {:schism, "~> 1.0", only: [:dev, :test]}

  ]

end

```

## Usage

Let's say that we have 5 nodes and we want to test what happens when they

disconnect from each other. We can use schism like so:

```elixir

test "netsplits" do

  [n1, n2, n3, n4, n5] = nodes

  # Partition our nodes

  Schism.partition([n1, n3])

  Schism.partition([n4])

  Schism.partition([n2, n5])

  # Test some stuff...

  # Heal our partitions

  Schism.heal([n1, n3])

  Schism.heal([n2, n4, n5])

end

```

This api is useful for testing and development in conjunction with tools like

[local cluster](https://github.com/whitfin/local-cluster) and [propcheck](https://github.com/alfert/propcheck).

It is not recommended that you use this in production.

## Things Schism doesn't do

Schism's reason for existing is to quickly and easily test netsplits between BEAMS

and it uses a rudimentary trick with cookies to achieve this goal. This is great

for quickly testing your system against faults.

But because of Schism's simple nature it should not be considered a replacement

for a more robust suite of tests. It *does not* test failed TCP connections,

interleaving of messages, race-conditions, clock skew, corruption, or any of

the other issues you will see in a distributed system.