Paxos Db

A replicated key value store that achieves consensus using multi-paxos.

Features

• Three types of operations can be performed on the server with the following parameters:
  • PUT (key, value)
  • GET (key)
  • DELETE (key)
• These operations are performed on a key value store.
• Server is multi threaded and can respond to multiple clients at a time.
• Client and servers communicate using RPC.
• The server is replicated across multiple instances.
• Replicas should be fault tolerant.
• Paxos is used for fault tolerant consensus.
• Replicas implement Paxos roles like the Proposers, Acceptors, and Learners.
• Clients can sent requests to any of the replicas.
• Only the replica that receives a client becomes the proposer for that round of paxos.
• A coordinator is present only for facilitating the discovery of all replicas.

Running instructions

The project uses maven for building. This project MUST be run with Docker or Docker Compose which will create a coordinator and the specified number of server replicas.

Run with Docker

Docker can be used along with the shell scripts.

# This script will build and start the coordinators and servers and then display logs from the coordinator
./deploy.sh

# To view logs from any of the 5 servers
docker logs server-<1-5> -f

# Run the client
./run_client.sh server-<1-5> <5001-5005>

Run with Docker Compose

You can also use docker compose to set it up

# Run the docker compose command
# This will create the network, start the coordinator and the specified number of replicas
docker compose up

# Run: 'docker compose down' when you want to remove the resources created above 

# Build client image
docker build -f client.Dockerfile -t client-img --target client-build .

# Run client container
docker run -it --rm --name client-con-1 --network project4_default client-img java -jar /app/client.jar project4-server-3 5001

# If the above command doesnt work (it didn't work for me on windows git bash) try this one
# docker run -it --rm --name client-con-1 --network project4_default client-img java -jar //app//client.jar project4-server-3 5001

If you want to change the number of replicas edit compose.yaml and rerun the commands.

replicas : 10

To change the ports that the servers run on you can also edit compose.yaml

coordinator:
    ...
    entrypoint: java -jar /app/server.jar c <coordinator port>
    ports:
        - "<coordinator port>:<coordinator port>"
    ...

server:
    ...
    entrypoint: java -jar /app/server.jar coordinator <coordinator port> <server port>
    ports:
        - target: <server port>
    ...