go-raft: A Go repository from cniles

Raft

This is a simple toy implementation of Raft using Go. Its a distributed state machine that stores logs with a consensus of what the current state is.

Build

To build, just run:

cd path/to/raft
go build

This produces a single binary, raft.

Run it with -h to show built-in command line help. It can either run as a server or be used to execute commands against a running cluster.

Running a cluster

To start a 3-node cluster, run the raft command three times, e.g. in three different terminals:

Terminal 1:

./raft -c ':9990,:9991,:9992' -p 9990

Terminal 2:

./raft -c ':9990,:9991,:9992' -p 9991

Terminal 3:

./raft -c ':9990,:9991,:9992' -p 9992

You can of course always choose to run them as daemon processes that write to files.

All three nodes should come up and elect a leader. They'll store their log files in your home directory under ~/.goraft/<agentId> where agentId is combination hostname_port.

Client commands

A log is really a command from the client to the cluster. The server can choose to do whatever it wants with the log.

For example, if you were building a database it could change the internal state somehow. This implementation doesn't do anything fancy with its logs though.

Appending a log

All commands are appended to the log.

The following would append the log "I like beer." to cluster member ":9990". It doesn't matter if its the leader or not, it will forward its request on (and tell you so much).

./raft -C "clientcommand" -m "I like beer." -S ":9990"

This doesn't make the server do much.

Print and Count

A message of print or count cause the server to write to their standard out when processed.

./raft -C "clientcommand" -m "count" -S ":9990"
./raft -C "clientcommand" -m "print" -S ":9990"

Would output the following on each server (depending on the state of the logs):

2024/02/23 17:52:24 Logs [i like beer count print]
2024/02/23 18:42:30 Count 3

Changing the cluster

It wouldn't be very fault tolerant machine if you couldn't add and remove machines from the cluster.

To add a new machine, start it with its agent id out of the configuratioion

./raft -c ':9990,:9991,:9992' -p ':9993'

Notice how :9993 is not in the provided list.

Then issue an addserver command to set the configuration to include the new server:

./raft -C addserver -m ":9993" -S ":9990"

Each server will announce the new peer, e.g.:

2024/02/23 18:43:20 Added new peer :9993

And the peer will be updated with logs it doesn't have. Any logs that it adds are processed.

The machine can similarly be removed with removeserver