Multiple key-value stores that reach consensus using Paxos

A fault-tolerant architecture to achieve consensus of updates amongst replicated state machine KV-store nodes using Paxos.

It's set up to allow multiple concurrent clients to communicate with any of the servers and perform three basic operations:

• PUT(key, value)
• GET(key)
• DELETE(key)

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Usage (locally):

1. Open up two terminal windows and navigate to /Project4/src
2. In one window, type javac node/*.java utils/*.java main/PaxosServerCreator.java (hit ↩), followed by java main.PaxosServerCreator (hit ↩)
3. The nodes are now running
4. In the other window, type javac client/*.java utils/*.java main/ClientMain.java (hit ↩), followed by java main.ClientMain <hostname> <port> (hit ↩)
5. The client is now running
6. The predefined protocol is:
   • PUT:key:value(hit ↩)
   • GET:key(hit ↩)
   • DELETE:key(hit ↩)
7. To pre-populate the nodes, type pp (hit ↩)
8. To shut down the application, type stop (hit ↩) or shutdown (hit ↩)

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SIDE NOTES

• Each node has a 10% chance of randomly failing in the prepare and accept phases.
• Other failure cases are the following:
• A client tries to delete a nonexistent key.
• A client tries to add an already existent key.
• At boot up, the user has to specify which node to connect to.