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Merged
achamayou merged 19 commits into from
Oct 29, 2025
Merged

PreVote enabled in TLA model checking #7404

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314ac46
Maybe done raft tla?
cjen1-msft Oct 17, 2025
5e3978e
Basic working
cjen1-msft Oct 23, 2025
a05f2ba
Make preVoteEnabled configurable for simulation
cjen1-msft Oct 23, 2025
bcb6ff2
Get model checking working?
cjen1-msft Oct 23, 2025
9db0cec
REVERT: test that a prevote leader can be elected.
cjen1-msft Oct 23, 2025
c674fef
Maybe tracing should also pass now?
cjen1-msft Oct 23, 2025
362fae2
Propagate UNCHANGED preVoteEnabled to all relevant points
cjen1-msft Oct 27, 2025
ac4a2e3
Only allow transitions from prevotecandidate to candidate
cjen1-msft Oct 27, 2025
727b249
Merge branch 'main' into pre-vote-tla
achamayou Oct 28, 2025
121bf96
Rough 3 state prevotestatus for CI
cjen1-msft Oct 28, 2025
7100bb6
Add debug non-trivial leader
cjen1-msft Oct 28, 2025
0d2a386
Remove debug inv from model checking
cjen1-msft Oct 28, 2025
e85c3dd
Snags
cjen1-msft Oct 28, 2025
c4504ee
Clarify membershipState of become.*Candidate
cjen1-msft Oct 28, 2025
c4891d9
Rejig naming
cjen1-msft Oct 28, 2025
70e7819
Constrain to only use pre-vote responses when a pre-vote candidate
cjen1-msft Oct 28, 2025
fd864cb
Make trace validation pass
cjen1-msft Oct 29, 2025
542ac53
Snag
cjen1-msft Oct 29, 2025
e90d623
Merge branch 'main' into pre-vote-tla
cjen1-msft Oct 29, 2025
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5 changes: 5 additions & 0 deletions tla/consensus/MCccfraft.cfg
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Expand Up @@ -15,10 +15,15 @@ CONSTANTS
Nil = Nil

Follower = L_Follower
PreVoteCandidate = L_PreVoteCandidate
Candidate = L_Candidate
Leader = L_Leader
None = L_None

PreVoteDisabled = PV_PreVoteDisabled
PreVoteCapable = PV_PreVoteCapable
PreVoteEnabled = PV_PreVoteEnabled

Active = R_Active
RetirementOrdered = R_RetirementOrdered
RetirementSigned = R_RetirementSigned
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3 changes: 3 additions & 0 deletions tla/consensus/MCccfraft.tla
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Expand Up @@ -106,10 +106,13 @@ MCSend(msg) ==
/\ n.type = AppendEntriesResponse
/\ CCF!Send(msg)

MCInitPreVoteStatus == PreVoteStatusTypeInv

MCInit ==
/\ InitMessagesVars
/\ InitCandidateVars
/\ InitLeaderVars
/\ MCInitPreVoteStatus
/\ IF Cardinality(Configurations[1]) = 1
\* If the first config is just one node, we can start with a two-tx log and a single config.
THEN InitLogConfigServerVars(Configurations[1], StartLog)
Expand Down
12 changes: 11 additions & 1 deletion tla/consensus/SIMccfraft.cfg
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Expand Up @@ -6,10 +6,15 @@ CONSTANTS
Nil = Nil

Follower = L_Follower
PreVoteCandidate = L_PreVoteCandidate
Candidate = L_Candidate
Leader = L_Leader
None = L_None

PreVoteDisabled = PV_PreVoteDisabled
PreVoteCapable = PV_PreVoteCapable
PreVoteEnabled = PV_PreVoteEnabled

Active = R_Active
RetirementOrdered = R_RetirementOrdered
RetirementSigned = R_RetirementSigned
Expand Down Expand Up @@ -51,6 +56,8 @@ CONSTANTS
Extend <- [abs]ABSExtend
CopyMaxAndExtend <- [abs]ABSCopyMaxAndExtend

InitPreVoteStatus <- SIMInitPreVoteStatus

_PERIODIC
Periodically

Expand All @@ -71,6 +78,8 @@ PROPERTIES
LeaderProp
LogMatchingProp

VotesGrantedMonotonicProp

\* ALIAS
\* \* DebugAlias
\* \* DebugActingServerAlias
Expand Down Expand Up @@ -115,4 +124,5 @@ INVARIANTS
\* DebugInvAllMessagesProcessable
\* DebugInvRetirementReachable
\* DebugInvUpToDepth
\* DebugMoreUpToDateCorrectInv
\* DebugMoreUpToDateCorrectInv
\* DebugNonTrivialLeaderInv
3 changes: 3 additions & 0 deletions tla/consensus/SIMccfraft.tla
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Expand Up @@ -16,6 +16,8 @@ SIMInitReconfigurationVars ==
\* Start with any subset of servers in the active configuration.
\/ CCF!InitReconfigurationVars

SIMInitPreVoteStatus == PreVoteStatusTypeInv

LOCAL R ==
1..IF "R" \in DOMAIN IOEnv THEN atoi(IOEnv.R) ELSE 10

Expand Down Expand Up @@ -66,6 +68,7 @@ SIMFairness ==
/\ \A s \in Servers : WF_vars(SignCommittableMessages(s))
/\ \A s \in Servers : WF_vars(AdvanceCommitIndex(s))
/\ \A s \in Servers : WF_vars(AppendRetiredCommitted(s))
/\ \A s \in Servers : WF_vars(PreVoteEnabled \in preVoteStatus /\ BecomeCandidate(s))
/\ \A s \in Servers : WF_vars(BecomeLeader(s))
\* The following fairness conditions reference the original CCF actions
\* and, thus, do not include the RandomElement conjunct.
Expand Down
7 changes: 7 additions & 0 deletions tla/consensus/Traceccfraft.cfg
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Expand Up @@ -54,13 +54,20 @@ CONSTANTS

InitReconfigurationVars <- TraceInitReconfigurationVars

InitPreVoteStatus <- TraceInitPreVoteStatus

Nil = Nil

Follower = L_Follower
PreVoteCandidate = L_PreVoteCandidate
Candidate = L_Candidate
Leader = L_Leader
None = L_None

PreVoteDisabled = PV_PreVoteDisabled
PreVoteCapable = PV_PreVoteCapable
PreVoteEnabled = PV_PreVoteEnabled

Active = R_Active
RetirementOrdered = R_RetirementOrdered
RetirementSigned = R_RetirementSigned
Expand Down
6 changes: 4 additions & 2 deletions tla/consensus/Traceccfraft.tla
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Expand Up @@ -111,6 +111,8 @@ TraceAppendEntriesBatchsize(i, j) ==
TraceInitReconfigurationVars ==
/\ InitLogConfigServerVars({TraceLog[1].msg.state.node_id}, StartLog)

TraceInitPreVoteStatus == PreVoteStatusTypeInv

-------------------------------------------------------------------------------------

VARIABLE l, ts
Expand Down Expand Up @@ -149,7 +151,7 @@ IsDropPendingTo ==
/\ IsEvent("drop_pending_to")
/\ Network!DropMessage(logline.msg.to_node_id,
LAMBDA msg: IsMessage(msg, logline.msg.to_node_id, logline.msg.from_node_id, logline))
/\ UNCHANGED <<reconfigurationVars, serverVars, candidateVars, leaderVars, logVars>>
/\ UNCHANGED <<preVoteStatus, reconfigurationVars, serverVars, candidateVars, leaderVars, logVars>>

IsTimeout ==
/\ IsEvent("become_candidate")
Expand Down Expand Up @@ -402,7 +404,7 @@ IsRcvProposeVoteRequest ==
/\ m.type = ProposeVoteRequest
/\ m.term = logline.msg.packet.term
/\ Discard(m)
/\ UNCHANGED <<commitIndex, reconfigurationVars, currentTerm, isNewFollower, leadershipState, log, matchIndex, membershipState, sentIndex, votedFor, votesGranted>>
/\ UNCHANGED <<preVoteStatus, commitIndex, reconfigurationVars, currentTerm, isNewFollower, leadershipState, log, matchIndex, membershipState, sentIndex, votedFor, votesGranted>>
/\ Range(logline.msg.state.committable_indices) \subseteq CommittableIndices(logline.msg.state.node_id)
/\ commitIndex[logline.msg.state.node_id] = logline.msg.state.commit_idx
/\ leadershipState[logline.msg.state.node_id] = ToLeadershipState[logline.msg.state.leadership_state]
Expand Down
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