Raf
Overview
Raf is an Elixir implementation of the Raft distributed consensus protocol. It provides users with an api for building consistent (2F+1 CP), distributed state machines. Raft protocol is described in the original paper.
Features
- Leader election
- Log replication
- Configuration changes
Installation
If available in Hex, the package can be installed
by adding raf to your list of dependencies in mix.exs:
def deps do
[
{:raf, "~> 0.1.0"}
]
endExample
Launch 3 nodes
$ iex --sname peer1@localhost -S mix
iex(peer1@localhost)1> Raf.start_test_node(:peer1)
$ iex --sname peer2@localhost -S mix
iex(peer2@localhost)1> Raf.start_test_node(:peer2)
$ iex --sname peer3@localhost -S mix
iex(peer3@localhost)1> Raf.start_test_node(:peer3)when peers have been running. You can check peers' status:
:sys.get_status(:peer1)
or
:sys.get_state(:peer1)Config cluster
At this point all the peers are in the follow state. In order to get them to communicate we need to define
a cluster configuration. In our case, we'll run on node peer1:
peers = [{:peer1, :peer1@localhost},
{:peer2, :peer2@localhost},
{:peer3, :peer3@localhost}]
Raf.set_config(:peer1, peers)Once election is done. You can see who is the current leader:
iex(peer2@localhost)3> Raf.get_leader(:peer2)
{:peer1, :peer1@localhost}Write Operations
# Create a new ets table
Raf.write(:peer1, {:new, :sometable})
# Store an erlang term in that table
Raf.write(:peer1, {:put, :sometable, :somekey, :someval})
# Delete a term from the table
Raf.write(:peer1, {:delete, :sometable, :somekey})
# Delete a table
Raf.write(:peer1, {:delete, :sometable})Read Operations
# Read an erlang term
Raf.read(:peer1, {:get, :sometable, :somekey})
# list tables
Raf.read(:peer1, :list_tables)
# list keys
Raf.read(:peer1, {:list_keys, :somekey})