Add voting and commit logic
This commit is contained in:
Marto
parent
a763d940da
commit
cd00bd097f
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@ -17,7 +17,21 @@ type
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VoteReplay = 1,
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Append = 2,
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AppendReplay = 3
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RaftRpcCode* = enum
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Rejected = 0,
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Accepted = 1
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RaftElectionResult* = enum
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Unknown = 0,
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Won = 1,
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Lost = 2
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RaftLogEntryType* = enum
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rletCommand = 0,
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rletConfig = 1,
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rletEmpty = 2
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RaftRpcAppendRequest* = object
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previousTerm: RaftNodeTerm
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@ -25,17 +39,48 @@ type
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commitIndex: RaftLogIndex
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entry: LogEntry
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RaftRpcAppendReplayRejected* = object
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nonMatchingIndex: RaftLogIndex
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lastIdx: RaftLogIndex
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RaftRpcAppendReplayAccepted* = object
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lastNewIndex: RaftLogIndex
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RaftRpcAppendReplay* = object
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commitIndex: RaftLogIndex
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term: RaftNodeTerm
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case result: RaftRpcCode:
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of Accepted: accepted: RaftRpcAppendReplayAccepted
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of Rejected: rejected: RaftRpcAppendReplayRejected
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RaftRpcVoteRequest* = object
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currentTerm: RaftNodeTerm
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lastLogIndex: RaftLogIndex
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lastLogTerm: RaftNodeTerm
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isPrevote: bool
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force: bool
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RaftRpcVoteReplay* = object
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currentTerm: RaftNodeTerm
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voteGranted: bool
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isPrevote: bool
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LeaderState* = object
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followersProgress: seq[RaftFollowerProgressTracker]
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RaftElectionTracker* = object
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all: seq[RaftNodeId]
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responded: seq[RaftNodeId]
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granted: int
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RaftVotes* = object
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voters: seq[RaftNodeId]
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current: RaftElectionTracker
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CandidateState* = object
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votes: seq[RaftNodeId]
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votes: RaftVotes
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isPrevote: bool
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FollowerState* = object
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leader: RaftNodeId
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@ -52,11 +97,16 @@ type
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Command* = object
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data: seq[byte]
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Config* = object
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LogEntry* = object # Abstarct Raft Node Log entry containing opaque binary data (Blob etc.)
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term: RaftNodeTerm
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index: RaftLogIndex
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# TODO: Add configuration too
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data: Command
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case kind: RaftLogEntryType:
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of rletCommand: command: Command
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of rletConfig: config: Config
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of rletEmpty: empty: bool
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RaftLog* = object
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logEntries: seq[LogEntry]
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@ -67,15 +117,20 @@ type
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committed: seq[LogEntry]
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messages: seq[RaftRpcMessage]
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debugLogs: seq[string]
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stateChange: bool
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RaftStateMachine* = object
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myId*: RaftNodeId
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term: RaftNodeTerm
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commitIndex: RaftLogIndex
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toCommit: RaftLogIndex
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log: RaftLog
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output: RaftStateMachineOutput
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electionTimeout: times.Duration
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lastUpdate: Time
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votedFor: RaftNodeId
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currentLeader: RaftNodeId
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pingLeader: bool
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case state: RaftNodeState
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of rnsFollower: follower : FollowerState
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of rnsCandidate: candidate: CandidateState
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@ -86,10 +141,59 @@ type
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RaftFollowerProgressTracker* = object
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id: RaftNodeId
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nextIndex: RaftLogIndex
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# Index of the highest log entry known to be replicated to this server.
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matchIndex: RaftLogIndex
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commitIndex: RaftLogIndex
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replayedIndex: RaftLogIndex
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func contains(a: seq[RaftNodeId], id: RaftNodeId): bool =
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var found = false
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for n in a:
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if n == id:
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found = true
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break
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return found
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func initElectionTracker*(nodes: seq[RaftNodeId]): RaftElectionTracker =
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var r = RaftElectionTracker()
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r.all = nodes
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r.granted = 0
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return r
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func registerVote*(ret: var RaftElectionTracker, nodeId: RaftNodeId, granted: bool): bool =
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if not ret.all.contains nodeId:
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return false
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if not ret.responded.contains nodeId:
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ret.responded.add(nodeId)
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ret.granted += 1
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return true
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func tallyVote*(ret: var RaftElectionTracker): RaftElectionResult =
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let quorym = int(len(ret.all) / 2) + 1
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if ret.granted > quorym:
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return RaftElectionResult.Won
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let unkown = len(ret.all) - len(ret.responded)
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if ret.granted + unkown > quorym:
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return RaftElectionResult.Unknown
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else:
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return RaftElectionResult.Lost
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func initVotes*(nodes: seq[RaftNodeId]): RaftVotes =
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var r = RaftVotes(voters: nodes, current: initElectionTracker(nodes))
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return r
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func registerVote*(rv: var RaftVotes, nodeId: RaftNodeId, granted: bool): bool =
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# TODO: Add support for configuration
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return rv.current.registerVote(nodeId, granted)
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func tallyVote*(rv: var RaftVotes): RaftElectionResult =
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# TODO: Add support for configuration
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return rv.current.tallyVote()
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func initFollowerProgressTracker*(follower: RaftNodeId, nextIndex: RaftLogIndex): RaftFollowerProgressTracker =
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return RaftFollowerProgressTracker(id: follower, nextIndex: nextIndex, matchIndex: 0, commitIndex: 0, replayedIndex: 0)
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@ -117,10 +221,16 @@ func lastIndex*(rf: RaftLog): RaftNodeTerm =
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let idx = len(rf.logEntries)
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return rf.logEntries[idx - 1].index
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func nextIndex*(rf: RaftLog): int =
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return rf.lastIndex + 1
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func truncateUncomitted*(rf: var RaftLog, index: RaftLogIndex) =
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# TODO: We should add support for configurations and snapshots
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rf.logEntries.delete(index..<len(rf.logEntries))
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func isUpToDate(rf: RaftLog, index: RaftLogIndex, term: RaftNodeTerm): bool =
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return term > rf.lastTerm or (term == rf.lastTerm and index >= rf.lastIndex)
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func getEntryByIndex(rf: RaftLog, index: RaftLogIndex): LogEntry =
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return rf.logEntries[index]
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@ -138,25 +248,27 @@ func appendAsFollower*(rf: var RaftLog, entry: LogEntry) =
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rf.logEntries.add(entry)
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func appendAsLeader*(rf: var RaftLog, term: RaftNodeTerm, index: RaftLogIndex, data: Command) =
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rf.appendAsLeader(LogEntry(term: term, index: index, data: data))
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rf.appendAsLeader(LogEntry(term: term, index: index, kind: rletCommand, command: data))
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func appendAsLeader*(rf: var RaftLog, term: RaftNodeTerm, index: RaftLogIndex, empty: bool) =
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rf.appendAsLeader(LogEntry(term: term, index: index, kind: rletEmpty, empty: true))
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func appendAsFollower*(rf: var RaftLog, term: RaftNodeTerm, index: RaftLogIndex, data: Command) =
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rf.appendAsFollower(LogEntry(term: term, index: index, data: data))
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rf.appendAsFollower(LogEntry(term: term, index: index, kind: rletCommand, command: data))
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func matchTerm*(rf: RaftLog, index: RaftLogIndex, term: RaftNodeTerm): bool =
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func matchTerm*(rf: RaftLog, index: RaftLogIndex, term: RaftNodeTerm): (bool, RaftNodeTerm) =
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if len(rf.logEntries) == 0:
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return true
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return (true, 0)
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# TODO: We should add support for snapshots
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if index > len(rf.logEntries):
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# The follower doesn't have all etries
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return false
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return (false, 0)
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if rf.logEntries[index].term == term:
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return true
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return (true, 0)
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else:
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return false
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return (false, rf.logEntries[index].term)
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func termForIndex*(rf: RaftLog, index: RaftLogIndex): RaftNodeTerm =
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# TODO: We should add support for snapshots
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@ -173,8 +285,16 @@ func initRaftStateMachine*(config: RaftStateMachineConfig): RaftStateMachine =
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return st
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func sendTo*(sm: var RaftStateMachine, id: RaftNodeId, request: RaftRpcAppendRequest) =
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sm.output.messages.add(RaftRpcMessage(currentTerm: sm.term, receiver: id, sender: sm.myId, kind: Append, appendRequest: request))
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sm.output.messages.add(RaftRpcMessage(currentTerm: sm.term, receiver: id, sender: sm.myId, kind: RaftRpcMessageType.Append, appendRequest: request))
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func sendTo*(sm: var RaftStateMachine, id: RaftNodeId, request: RaftRpcAppendReplay) =
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sm.output.messages.add(RaftRpcMessage(currentTerm: sm.term, receiver: id, sender: sm.myId, kind: RaftRpcMessageType.AppendReplay, appendReplay: request))
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func sendTo*(sm: var RaftStateMachine, id: RaftNodeId, request: RaftRpcVoteRequest) =
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sm.output.messages.add(RaftRpcMessage(currentTerm: sm.term, receiver: id, sender: sm.myId, kind: RaftRpcMessageType.Vote, voteRequest: request))
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func sendTo*(sm: var RaftStateMachine, id: RaftNodeId, request: RaftRpcVoteReplay) =
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sm.output.messages.add(RaftRpcMessage(currentTerm: sm.term, receiver: id, sender: sm.myId, kind: RaftRpcMessageType.VoteReplay, voteReplay: request))
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func createVoteRequest*(sm: var RaftStateMachine): RaftRpcMessage =
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return RaftRpcMessage(currentTerm: sm.term, sender: sm.myId, kind: Vote, voteRequest: RaftRpcVoteRequest())
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@ -220,11 +340,20 @@ func advance*(sm: var RaftStateMachine, msg: RaftRpcMessage,currentTime: Time) =
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else:
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sm.debug "Unhandle msg type"
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func addEntry*(sm: var RaftStateMachine, entry: LogEntry) =
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if sm.state != RaftNodeState.rnsLeader:
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sm.debug "Error: only the leader can handle new entries"
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sm.log.appendAsLeader(entry)
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func addEntry*(sm: var RaftStateMachine, command: Command) =
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sm.addEntry(LogEntry(term: sm.term, index: sm.log.nextIndex, kind: rletCommand, command: command))
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func addEntry*(sm: var RaftStateMachine, config: Config) =
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sm.addEntry(LogEntry(term: sm.term, index: sm.log.nextIndex, kind: rletConfig, config: config))
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func addEmptyEntry*(sm: var RaftStateMachine) =
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sm.addEntry(LogEntry(term: sm.term, index: sm.log.nextIndex, kind: rletEmpty, empty: true))
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func tick* (sm: var RaftStateMachine) =
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sm.debug "TODO:implement tick"
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@ -240,6 +369,139 @@ func poll*(sm: var RaftStateMachine): RaftStateMachineOutput =
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func commit*(sm: var RaftStateMachine) =
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if sm.state != RaftNodeState.rnsLeader
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if sm.state != RaftNodeState.rnsLeader:
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return
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var new_index = sm.commitIndex
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var next_index = sm.commitIndex + 1
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while next_index < sm.log.lastIndex:
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var replicationCnt = 0
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for p in sm.leader.followersProgress:
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if p.matchIndex > new_index:
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replicationCnt += 1
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if replicationCnt > len(sm.leader.followersProgress):
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sm.output.committed.add(sm.log.getEntryByIndex(next_index))
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sm.commitIndex += next_index;
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next_index += 1
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func find_follower_proggress_by_id(sm: var RaftStateMachine, id: RaftNodeId): Option[RaftFollowerProgressTracker] =
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for follower in sm.leader.followersProgress:
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if follower.id == id:
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return some(follower)
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return none(RaftFollowerProgressTracker)
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func append_entry_reply*(sm: var RaftStateMachine, from_id: RaftNodeId, replay: RaftRpcAppendReplay) =
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if sm.state != RaftNodeState.rnsLeader:
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sm.debug "You can't append append replay to the follower"
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return
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var follower = sm.find_follower_proggress_by_id(from_id)
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if not follower.isSome:
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sm.debug "Can't find the follower"
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return
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follower.get().commitIndex = max(follower.get().commitIndex, replay.commitIndex)
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case replay.result:
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of RaftRpcCode.Accepted:
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let lestIndex = replay.accepted.lastNewIndex
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follower.get().accepted(lestIndex)
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# TODO: add leader stepping down logic here
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sm.commit()
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if sm.state != RaftNodeState.rnsLeader:
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return
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of RaftRpcCode.Rejected:
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if replay.rejected.nonMatchingIndex == 0 and replay.rejected.lastIdx == 0:
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sm.replicateTo(follower.get())
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follower.get().next_index = min(replay.rejected.nonMatchingIndex, replay.rejected.lastIdx + 1)
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# if commit apply configuration that removes current follower
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# we should take it again
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var follower2 = sm.find_follower_proggress_by_id(from_id)
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if follower2.isSome:
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sm.replicate_to(follower2.get())
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func advance_commit_idx(sm: var RaftStateMachine, leaderIdx: RaftLogIndex) =
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let new_idx = min(leaderIdx, sm.log.lastIndex)
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if new_idx > sm.commitIndex:
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sm.commitIndex = new_idx
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# TODO: signal the output for the update
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func append_entry*(sm: var RaftStateMachine, from_id: RaftNodeId, request: RaftRpcAppendRequest) =
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if sm.state != RaftNodeState.rnsFollower:
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sm.debug "You can't append append request to the non follower"
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return
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let (match, term) = sm.log.matchTerm(request.previousLogIndex, request.previousTerm)
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if not match:
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let rejected = RaftRpcAppendReplayRejected(nonMatchingIndex: request.previousLogIndex, lastIdx: sm.log.lastIndex)
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let responce = RaftRpcAppendReplay(term: sm.term, commitIndex: sm.commitIndex, result: RaftRpcCode.Rejected, rejected: rejected)
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sm.send_to(sm.myId, responce)
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sm.debug "Reject to apply the entry"
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# reject to apply
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#send_to()
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sm.log.appendAsFollower(request.entry)
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sm.advance_commit_idx(request.commitIndex)
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let accepted = RaftRpcAppendReplayAccepted(lastNewIndex: sm.log.lastIndex)
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let responce = RaftRpcAppendReplay(term: sm.term, commitIndex: sm.commitIndex, result: RaftRpcCode.Accepted, accepted: accepted)
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sm.send_to(sm.myId, responce)
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func request_vote*(sm: var RaftStateMachine, from_id: RaftNodeId, request: RaftRpcVoteRequest, ) =
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let canVote = sm.votedFor == from_id or (sm.votedFor == RaftNodeId() and sm.currentLeader == RaftNodeId()) or (request.isPrevote and request.currentTerm > sm.term)
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if canVote and sm.log.isUpToDate(request.lastLogIndex, request.lastLogTerm):
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if not request.is_prevote:
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# TODO: Update election time
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sm.votedFor = from_id
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let responce = RaftRpcVoteReplay(currentTerm: sm.term, voteGranted: true, isPrevote: request.is_prevote)
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sm.send_to(sm.myId, responce)
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else:
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let responce = RaftRpcVoteReplay(currentTerm: sm.term, voteGranted: false, isPrevote: request.is_prevote)
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sm.send_to(sm.myId, responce)
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func becomeFollower*(sm: var RaftStateMachine, leaderId: RaftNodeId) =
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if sm.myId == leaderId:
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sm.debug "Can't be follower of itself"
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sm.output.stateChange = sm.state != RaftNodeState.rnsFollower
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sm.state = RaftNodeState.rnsFollower
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sm.follower = FollowerState(leader: leaderId)
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if leaderId != RaftnodeId():
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sm.pingLeader = false
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# TODO: Update last election time
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func becomeLeader*(sm: var RaftStateMachine) =
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if sm.state == RaftNodeState.rnsLeader:
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sm.debug "The leader can't become leader second time"
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return
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sm.output.stateChange = true
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sm.state = RaftnodeState.rnsLeader
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sm.leader = LeaderState()
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sm.pingLeader = false
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#TODO: Update last election time
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#TODO: setup the tracket
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sm.addEmptyEntry()
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return
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func becomeCandidate*(sm: var RaftStateMachine, isPrevote: bool) =
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#TODO: implement
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return
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func request_vote_reply*(sm: var RaftStateMachine, from_id: RaftNodeId, request: RaftRpcVoteReplay) =
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if sm.state != RaftNodeState.rnsCandidate:
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sm.debug "Non candidate can't handle votes"
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return
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discard sm.candidate.votes.registerVote(from_id, request.voteGranted)
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case sm.candidate.votes.tallyVote:
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of RaftElectionResult.Unknown:
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return
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of RaftElectionResult.Won:
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sm.debug "Win election"
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if (sm.candidate.isPrevote):
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sm.becomeCandidate(false)
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else:
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sm.becomeLeader()
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of RaftElectionResult.Lost:
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sm.debug "Lost election"
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sm.becomeFollower(RaftNodeId())
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# TODO: become foller
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