jonasuj/dsys-hw4

Distributed Systems Homework 4

dsys-hw4

Distrubuted Systems Homework #4

$ go run . -help
Usage of dsys-hw4:
  -name string
        Name of this instance (default "<no name>")
  -port string
        Port to listen on (default "50050")

name is used solely for naming log files; logs are written to <name>.log. A handy way to view the logs once all processes are running is tail -fqn 0 *.log. Or to view the logs retroactively try sort -k3 *.log, and better yet, combine them sort -k3 *.log | tail -n10 && tail -fqn0 *.log :)

Run

To start a process, run go run . -name A -port 5000 - it'll display a message once it's ready to receive input. Do this a couple more times to start more processes.

Each process represents a peer in a peer-to-peer style network (a complete graph). To connect these peers in a, type the command connect <port> into stdin for a source peer, where <port> is the port number of the target peer. The connection graph of the source and target will then form a new complete graph (where all peers are connected). In other words, just run connect once in the first peer for each other peer, and they should all connect up nicely.

Taking the lock

... and entering the critical section. There are two commands beside connect: lock and unlock.Unsurprisingly, lock will attempt to enter the critical section, coordinating with all other peers to make sure only one is allowed in at a time. Likewise, unlock will exit the critical section immediately.

Why it's correct

We've implemented the Ricart-Agrawala algorithm as presented in the lecture. To make its correctness as obvious as possible, we've implemented it as an interface in its own file where each line of code almost corresponds one-to-one with the pseudo-code from the slides. Additionally, we're reusing our Lamport time implementation (slightly modified) from a previous assignment which we know to be correct because it was accepted.