# nim-raft # Copyright (c) 2023 Status Research & Development GmbH # Licensed under either of # * Apache License, version 2.0, ([LICENSE-APACHE](LICENSE-APACHE)) # * MIT license ([LICENSE-MIT](LICENSE-MIT)) # at your option. # This file may not be copied, modified, or distributed except according to # those terms. # Raft Node Public Types import std/rlocks import options import stew/results import uuids import chronos export results, options, rlocks, uuids, chronos const DefaultUUID* = initUUID(0, 0) # 00000000-0000-0000-0000-000000000000 type RaftNodeState* = enum rnsUnknown = 0, rnsFollower = 1, rnsCandidate = 2 rnsLeader = 3, rnsStopped = 4 RaftNodeId* = UUID # uuid4 uniquely identifying every Raft Node RaftNodeTerm* = uint64 # Raft Node Term Type RaftLogIndex* = uint64 # Raft Node Log Index Type RaftNodePeer* = ref object # Raft Node Peer object id*: RaftNodeId nextIndex*: RaftLogIndex # For each peer Raft Node, index of the next log entry to send to that Node # (initialized to leader last log index + 1) matchIndex*: RaftLogIndex # For each peer Raft Node, index of highest log entry known to be replicated on Node # (initialized to 0, increases monotonically) hasVoted*: bool # Indicates if this peer have voted for this Raft Node During Election canVote*: bool # Indicates if this peer can vote RaftNodePeers* = seq[RaftNodePeer] # List of Raft Node Peers # Raft Node Abstract State Machine type RaftNodeStateMachine*[SmCommandType, SmStateType] = ref object # Some opaque State Machine Impelementation to be used by the Raft Node # providing at minimum operations for initialization, querying the current state # and RaftNodeLogEntry (SmCommandType) application state*: ref SmStateType # Raft Node Persistent Storage basic definition RaftNodePersistentStorage*[SmCommandType, SmStateType] = object # Should be some kind of Persistent Transactional Store Wrapper # Basic modules (algos) definitions RaftNodeAccessCallback[SmCommandType, SmStateType] = proc: RaftNode[SmCommandType, SmStateType] {.nimcall, gcsafe.} # This should be implementes as a closure holding the RaftNode RaftConsensusModule*[SmCommandType, SmStateType] = object of RootObj stateTransitionsFsm: seq[byte] # I plan to use nim.fsm https://github.com/ba0f3/fsm.nim gatheredVotesCount: int raftNodeAccessCallback: RaftNodeAccessCallback[SmCommandType, SmStateType] RaftLogCompactionModule*[SmCommandType, SmStateType] = object of RootObj raftNodeAccessCallback: RaftNodeAccessCallback[SmCommandType, SmStateType] RaftMembershipChangeModule*[SmCommandType, SmStateType] = object of RootObj raftNodeAccessCallback: RaftNodeAccessCallback[SmCommandType, SmStateType] # Callback for sending messages out of this Raft Node RaftMessageId* = UUID # UUID assigned to every Raft Node Message, # so it can be matched with it's corresponding response etc. # Raft Node Messages OPs RaftMessageOps* = enum rmoRequestVote = 0, # Request Raft Node vote during election. rmoAppendLogEntry = 1, # Append log entry (when replicating) or represent a Heart-Beat # if log entries are missing. rmoInstallSnapshot = 2 # For dynamic adding of new Raft Nodes to speed up the new nodes # when they have to catch-up to the currently replicated log. RaftMessageBase* = ref object of RootObj # Base Type for Raft Protocol Messages. op*: RaftMessageOps # Message op. Used to distinguish between different message types # and cast the base class to the correct derived class where necessary. msgId*: RaftMessageId # Message UUID. senderId*: RaftNodeId # Sender Raft Node ID. receiverId*: RaftNodeId # Receiver Raft Node ID. RaftMessageResponseBase* = ref object of RaftMessageBase RaftMessageSendCallback* = proc (raftMessage: RaftMessageBase): Future[RaftMessageResponseBase] {.async, gcsafe.} # Callback for Sending Raft Node Messages # out of this Raft Node. # For later use when adding/removing new nodes (dynamic configuration chganges) RaftNodeConfiguration* = ref object peers*: RaftNodePeers # Raft Node Log definition LogEntryType* = enum etUnknown = 0, etConfiguration = 1, etData = 2, etNoOp = 3 RaftNodeLogEntry*[SmCommandType] = object # Abstarct Raft Node Log entry containing opaque binary data (Blob etc.) term*: RaftNodeTerm index*: RaftLogIndex entryType*: LogEntryType # Type of entry - data to append, configuration or no op etc. data*: Option[SmCommandType] # Entry data (State Machine Command) - this is mutually exclusive with configuration # depending on entryType field configuration*: Option[RaftNodeConfiguration] # Node configuration RaftNodeLog*[SmCommandType] = object # Needs more elaborate definition. # Probably this will be a RocksDB/MDBX/SQLite Store Wrapper etc. logData*: seq[RaftNodeLogEntry[SmCommandType]] # Raft Node Log Data RaftTimerCallback* = proc () {.gcsafe.} # Pass any function wrapped in a closure # Raft Node Object type RaftNode*[SmCommandType, SmStateType] = ref object # Timers votesFuts*: seq[Future[RaftMessageResponseBase]] requestVotesTimeout*: int heartBeatTimeout*: int appendEntriesTimeout*: int heartBeatTimer*: Future[void] electionTimeoutTimer*: Future[void] appendEntriesTimer*: Future[void] # Mtx definition(s) go here raftStateMutex*: RLock # Misc msgSendCallback*: RaftMessageSendCallback persistentStorage: RaftNodePersistentStorage[SmCommandType, SmStateType] # Persistent state id*: RaftNodeId # This Raft Node ID state*: RaftNodeState # This Raft Node State currentTerm*: RaftNodeTerm # Latest term this Raft Node has seen (initialized to 0 on first boot, increases monotonically) votedFor*: RaftNodeId # Candidate RaftNodeId that received vote in current term (or DefaultUUID if none), # also used to redirect Client Requests in case this Raft Node is not the leader log: RaftNodeLog[SmCommandType] # This Raft Node Log stateMachine*: RaftNodeStateMachine[SmCommandType, SmStateType] # Not sure for now putting it here. I assume that persisting the State Machine's # state is enough to consider it 'persisted' peers*: RaftNodePeers # This Raft Node Peers IDs. I am not sure if this must be persistent or volatile but making it persistent # makes sense for the moment # Volatile state commitIndex*: RaftLogIndex # Index of highest log entry known to be committed (initialized to 0, increases monotonically) lastApplied*: RaftLogIndex # Index of highest log entry applied to state machine (initialized to 0, increases monotonically) currentLeaderId*: RaftNodeId # The ID of the current leader Raft Node or DefaultUUID if None is leader (election is in progress etc.)