This is an Elixir implementation of a variant of the Paxos algorithm, as described in the paper Paxos Made Moderately Complex (Robbert van Renesse and Deniz Altınbüken). Paxos is a consensus algorithm, a fundamental problem in distributed computing.
We model several servers, each of which maintains a replica of a ledger. They all Service a number of clients, who broadcast transactions. Our ledger replicas must guarantee:
- Consistency: transactions are appended in the same order to all ledgers
- Liveness: all transactions will eventually be appended
- Safety: only transactions broadcast by clients will be appended
- Failure tolerance: as long as a majority of replicas is correct (ie, have not crashed), we will maintain Consistency, Liveness, and Safety.
The resulting architecture is not simple:
Every module is its own Elixir process, and no global concurrency primitives (like locks or semaphores) are used at all. This is a non-blocking, partially asynchronous distributed system.
For a more detailed implementation description, see the report.
To see possible running configuraitons, see configuration.ex file.
Change running configurations as variable in Makefile.
The prevent_livelock ones are the most relevant ones!
make clean - remove compiled code
make compile - compile
make run - same as make run SERVERS=5 CLIENTS=5 CONFIG=default DEBUG=0 MAX_TIME=15000