raft-grpc-kv

IMPORTANT: Do not use any part of this project for production. It is not meant to be representative of how resilient distributed raft-based systems are built. It's simply an experiment by the sleep-deprived author to see how it works.

With that out of the way, this is a simple experiment to see how to use gRPC and Raft together to implement an (INCREDIBLY BASIC) in-memory key-value store.

Related reading/watching

• The Practical Distributed Consensus using HashiCorp/raft was the inspiration for this project. The code linked in the video is available on GitHub (though it's a few years old at this point).
• Another toy KV store implementation using Raft

Structure

• ./cmd/kvd -- the server implementation (exposes a GRPC interface)
• ./cmd/kv -- the client implementation
• ./pkg/fsm -- the implementation of the Raft FSM
• ./api -- definition of the gRPC API

Usage

Build the binaries:

make

Start each of the servers in separate terminals:

# Initial node (bootstraps due to empty --join-address flag)
./bin/kvd --grpc-address 127.0.0.1:8080 --raft-address 127.0.0.1:7080

# Second node
./bin/kvd --grpc-address 127.0.0.1:8081 --raft-address 127.0.0.1:7081 --join-address 127.0.0.1:8080

# Third node
./bin/kvd --grpc-address 127.0.0.1:8082 --raft-address 127.0.0.1:7082 --join-address 127.0.0.1:8080

Use the client to interact:

./bin/kv get foo
# Error: rpc error: code = NotFound desc = key "foo" not found

./bin/kv set foo bar

# Query the default node (:8080)
./bin/kv get foo
# bar

# Query a follower node (:8081)
./bin/kv get --address 127.0.0.1:8081 foo
# bar

Next steps

• Currently, kv set requests must be directed to the leader. I'd like to automagically forward these to the leader if the gRPC request is handled by a follower.