aarondb/raft

Types

RaftEffect

Effects that the transactor must execute after a state transition. This de-complects the pure state machine from side effects.

pub type RaftEffect {
  SendHeartbeat(to: process.Pid, term: Int, leader: process.Pid)
  SendVoteRequest(
    to: process.Pid,
    term: Int,
    candidate: process.Pid,
  )
  SendVoteResponse(to: process.Pid, term: Int, granted: Bool)
  RegisterAsLeader
  UnregisterAsLeader
  ResetElectionTimer
  StartHeartbeatTimer
  StopHeartbeatTimer
}

Constructors

SendHeartbeat(to: process.Pid, term: Int, leader: process.Pid)

SendVoteRequest(
  to: process.Pid,
  term: Int,
  candidate: process.Pid,
)

SendVoteResponse(to: process.Pid, term: Int, granted: Bool)

```
RegisterAsLeader
```
```
UnregisterAsLeader
```
```
ResetElectionTimer
```
```
StartHeartbeatTimer
```
```
StopHeartbeatTimer
```

RaftMessage

Messages the Raft state machine can process.

pub type RaftMessage {
  Heartbeat(term: Int, leader: process.Pid)
  HeartbeatResponse(term: Int, from: process.Pid)
  VoteRequest(term: Int, candidate: process.Pid)
  VoteResponse(term: Int, granted: Bool, from: process.Pid)
  ElectionTimeout
  HeartbeatTick
}

Constructors

Heartbeat(term: Int, leader: process.Pid)

HeartbeatResponse(term: Int, from: process.Pid)

VoteRequest(term: Int, candidate: process.Pid)

VoteResponse(term: Int, granted: Bool, from: process.Pid)

```
ElectionTimeout
```
```
HeartbeatTick
```

RaftRole

The three roles in Raft’s election protocol.

pub type RaftRole {
  Follower
  Candidate
  Leader
}

Constructors

```
Follower
```
```
Candidate
```
```
Leader
```

RaftState

The pure state of the Raft election state machine. No side effects — the transactor interprets the effects.

pub type RaftState {
  RaftState(
    role: RaftRole,
    current_term: Int,
    voted_for: option.Option(process.Pid),
    peers: List(process.Pid),
    votes_received: Int,
    leader_pid: option.Option(process.Pid),
  )
}

Constructors

RaftState(
  role: RaftRole,
  current_term: Int,
  voted_for: option.Option(process.Pid),
  peers: List(process.Pid),
  votes_received: Int,
  leader_pid: option.Option(process.Pid),
)

Values

add_peer

pub fn add_peer(state: RaftState, peer: process.Pid) -> RaftState

Add a peer to the cluster.

handle_message

pub fn handle_message(
  state: RaftState,
  msg: RaftMessage,
  self_pid: process.Pid,
) -> #(RaftState, List(RaftEffect))

Process a Raft message and return the new state + effects. This is the ONLY entry point. It is pure — no side effects.

is_leader

pub fn is_leader(state: RaftState) -> Bool

Check if this node is the current leader.

new

pub fn new(peers: List(process.Pid)) -> RaftState

Create a new Raft state in Follower role at term 0.

remove_peer

pub fn remove_peer(
  state: RaftState,
  peer: process.Pid,
) -> RaftState

Remove a peer from the cluster.