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https://github.com/eliben/raft

:rowboat: Raft implementation in Go
https://github.com/eliben/raft

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:rowboat: Raft implementation in Go

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# :rowboat: Raft



This is an instructional implementation of the Raft distributed consensus

algorithm in Go. It's accompanied by a series of blog posts:



* [Part 0: Introduction](https://eli.thegreenplace.net/2020/implementing-raft-part-0-introduction/)

* [Part 1: Elections](https://eli.thegreenplace.net/2020/implementing-raft-part-1-elections/)

* [Part 2: Commands and log replication](https://eli.thegreenplace.net/2020/implementing-raft-part-2-commands-and-log-replication/)

* [Part 3: Persistence and optimizations](https://eli.thegreenplace.net/2020/implementing-raft-part-3-persistence-and-optimizations/)



Each of the `partN` directories in this repository is the complete source code

for Part N of the blog post series (except Part 0, which is introductory and has

no code). There is a lot of duplicated code between the different `partN`

directories - this is a conscious design decision. Rather than abstracting and

reusing parts of the implementation, I opted for keeping the code as simple

as possible. Each directory is completely self contained and can be read and

understood in isolation. Using a graphical diff tool to see the deltas between

the parts can be instructional.



## How to use this repository



You can read the code, but I'd also encourage you to run tests and observe the

logs they print out. The repository contains a useful tool for visualizing

output. Here's a complete usage example:



```

$ cd part1

$ go test -v -race -run TestElectionFollowerComesBack |& tee /tmp/raftlog

... logging output

... test should PASS

$ go run ../tools/raft-testlog-viz/main.go < /tmp/raftlog

PASS TestElectionFollowerComesBack map[0:true 1:true 2:true TEST:true] ; entries: 150

... Emitted file:///tmp/TestElectionFollowerComesBack.html



PASS

```



Now open `file:///tmp/TestElectionFollowerComesBack.html` in your browser.

You should see something like this:



![Image of log browser](https://github.com/eliben/raft/blob/master/raftlog-screenshot.png)



Scroll and read the logs from the servers, noticing state changes (highlighted

with colors). Feel free to add your own `cm.dlog(...)` calls to the code to

experiment and print out more details.



## Changing and testing the code



Each `partN` directory is completely independent of the others, and is its own

Go module. The Raft code itself has no external dependencies; the only `require`

in its `go.mod` is for a package that enables goroutine leak testing - it's only

used in tests.



To work on `part2`, for example:



```

$ cd part2

... make code changes

$ go test -race ./...

```



Depending on the part and your machine, the tests can take up to a minute to

run. Feel free to enable verbose logging with ``-v``, and/or used the provided

``dotest.sh`` script to run specific tests with log visualization.



## Contributing



I'm interested in hearing your opinion or suggestions for the code in this

repository. Feel free to open an issue if something is unclear, or if you think

you found a bug. Code contributions through PRs are welcome as well.