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83 lines
4.1 KiB
Nim
83 lines
4.1 KiB
Nim
# nim-raft
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# Copyright (c) 2023 Status Research & Development GmbH
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# Licensed under either of
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# * Apache License, version 2.0, ([LICENSE-APACHE](LICENSE-APACHE))
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# * MIT license ([LICENSE-MIT](LICENSE-MIT))
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# at your option.
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# This file may not be copied, modified, or distributed except according to
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# those terms.
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import std/tables
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import std/rlocks
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import types
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type
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# Node events
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EventType = enum
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NodeStart, NodeStop, NodeTick, NodeStepDown, NodeStepDownToCandidate, NodeStepDownToFollower, NodeStepDownToLeader,
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NodeStepDownToShutdown, VotingTimeout, ElectionTimeout, HeartbeatTimeout, HeartbeatReceived, HeartbeatSent, AppendEntriesReceived,
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AppendEntriesSent, RequestVoteReceived, RequestVoteSent, RequestVoteGranted, RequestVoteDenied, ClientRequestReceived,
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ClientRequestSent, ClientRequestProcessed, ClientRequestFailed, ClientRequestTimeout, ClientRequestRetry, ClientRequestRetryExhausted,
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AddNewNode, RemoveNode, NodeShutdown, NodeShutdownComplete, NodeShutdownFailed, NodeShutdownTimeout, NodeShutdownRetry
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# Define callback to use with Terminals. Node states are updated/read in-place in the node object
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ConsensusFSMCallbackType*[NodeType] = proc(node: NodeType) {.gcsafe.}
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# Define Non-Terminals as a (unique) tuples of the internal state and a sequence of callbacks
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NonTerminalSymbol*[NodeType] = (NodeType, seq[ConsensusFSMCallbackType[NodeType]])
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# Define logical functions (conditions) computed from our NodeType etc. (Truth Table)
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LogicalFunctionConditionValueType* = bool
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LogicalFunctionCondition*[EventType, NodeTytpe, RaftMessageBase] = proc(e: EventType, n: NodeTytpe, msg: Option[RaftMessageBase]): bool
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LogicalFunctionConditionsLUT*[EventType, NodeType, RaftMessageBase] = Table[(EventType, NodeType), seq[LogicalFunctionCondition[EventType, NodeType, Option[RaftMessageBase]]]]
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# Define Terminals as a tuple of a Event and a sequence of logical functions (conditions) and their respective values computed from NodeType, NodeTytpe and RaftMessageBase
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# (kind of Truth Table)
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TerminalSymbol*[EventType, NodeType, RaftMessageBase] = (EventType, seq[LogicalFunctionConditionValueType])
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# Define State Transition Rules LUT of the form ( NonTerminal -> Terminal ) -> NonTerminal )
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StateTransitionsRulesLUT*[NodeType, EventType, RaftMessageBase] = Table[
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(NonTerminalSymbol[NodeType], TerminalSymbol[NodeType, EventType, RaftMessageBase]),
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NonTerminalSymbol[NodeType]]
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# FSM type definition
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ConsensusFSM*[NodeType, EventType, BaseRaftMessage] = ref object
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mtx: RLock
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state: NonTerminalSymbol[NodeType]
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stateTransitionsLUT: StateTransitionsRulesLUT[NodeType, EventType, RaftMessageBase]
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logicalFunctionsLut: LogicalFunctionConditionsLUT[EventType, NodeType, RaftMessageBase]
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# FSM type constructor
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proc new*[NodeType, EventType, NodeStates](T: type ConsensusFSM[NodeType, EventType, RaftMessageBase],
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lut: StateTransitionsRulesLUT[NodeType, EventType, RaftMessageBase],
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startSymbol: NonTerminalSymbol[NodeType]
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): T =
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result = new(ConsensusFSM[NodeType, EventType, NodeStates])
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initRLock(result.mtx)
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result.state = startSymbol
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result.stateTransitionsLUT = lut
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proc computeFSMLogicFunctionsPermutationValue[NonTerminalSymbol, NodeType, EventType, RaftMessageBase](
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fsm: ConsensusFSM[NodeType, EventType, RaftMessageBase],
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nts: NonTerminalSymbol, rawInput: TerminalSymbol, msg: Option[RaftMessageBase]): TerminalSymbol =
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let
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e = rawInput[0]
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var
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logicFunctionsConds = fsm.logicalFunctionsLut[(e, NodeType)]
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for f in logicFunctionsConds:
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f = f(nts[1], e, msg)
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rawInput[1] = logicFunctionsConds
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result = rawInput
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proc consensusFSMAdvance[NodeType, EventType](fsm: ConsensusFSM[NodeType, EventType, RaftMessageBase], node: NodeType, event: EventType,
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rawInput: TerminalSymbol[EventType, NodeType, RaftMessageBase], msg: Option[RaftMessageBase]): NonTerminalSymbol[NodeType] =
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withRLock():
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var
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input = computeFSMLogicFunctionsPermutationValue(fsm, node, event, rawInput)
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fsm.state = fsm.stateTransitionsLUT[(fsm.state, input)]
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result = fsm.state
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