https://github.com/djo/leader_election

Leader Election Implementation
https://github.com/djo/leader_election

Last synced: over 1 year ago
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Leader Election Implementation

• Host: GitHub
• URL: https://github.com/djo/leader_election
• Owner: djo
• Created: 2014-04-17T19:33:02.000Z (about 12 years ago)
• Default Branch: master
• Last Pushed: 2014-10-06T13:10:19.000Z (over 11 years ago)
• Last Synced: 2025-02-03T19:07:04.089Z (over 1 year ago)
• Language: Erlang
• Homepage:
• Size: 258 KB
• Stars: 4
• Watchers: 2
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md

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README

          
## Leader Election Algorithm

[![Build Status](https://travis-ci.org/Djo/leader_election.svg)](https://travis-ci.org/Djo/leader_election)

[The bully algorithm](http://en.wikipedia.org/wiki/Bully_algorithm) is one of methods in [distributed computing](http://en.wikipedia.org/wiki/Distributed_computing) for implementation of the [leader election](http://en.wikipedia.org/wiki/Leader_election) process for dynamically electing a coordinator by process ID number. The process with the highest number is selected as the coordinator.

### Build

To run the algorithm you need a working installation of Erlang R15BXX (or later).

    $ make get-deps

    $ make compile-all

### Usage

Configure `timeout` and `nodes` in the `bully.config`.

    $ ./start.sh 1@127.0.0.1

    $ ./start.sh 2@127.0.0.1

    $ ./start.sh 3@127.0.0.1

    $ ./start.sh 4@127.0.0.1

Then you can kill a node and see logs.

### Description

Implementation consists of monitoring of the current leader and election a new one

when the current is unavailable. The election of a new leader should be done as soon as possible.

You have a distributed network from `N` nodes where each node described by an unique identity number.

#### Monitoring of the current leader

Each node sends `ping` every `T` seconds to the current leader and waits `4*T` seconds for `pong` reply.

On the waiting timeout the leader election process should be started.

#### Leader election process

1. A node started the election starts sending `announce election` to all nodes

   with a higher identity number and waits for `ok`.

    * If no one `ok` after `T` seconds the node starts leading and sends `new leader` to all nodes.

    * If received `ok` the node starts waiting for `new leader` next `T` seconds.

      On `new leader` waiting timeout the node starts announcing election again.

2. When receiving `announce election` a node replies with `ok` and starts the election process itself.

    * If the node received `announce election` is with the highest identity number it starts leading

      with sending `new leader` to all nodes.

3. When receiving `new leader` a node saves a new leader and starts monitoring it.

#### Example

![Example](https://raw.github.com/Djo/leader_election/master/example.png)

Inspired by an article about a test task from [aboutecho.com](http://www.echorussia.ru/jobs/serverside-june-2013.html).

Copyright (C) 2014 [Andrew Djoga](http://andrewdjoga.com), released under the MIT license.