myxce/.kiro/specs/raft-ha-core-safety/tasks.md

Implementation Plan: raft-ha-core-safety

TDD (project steering, mandatory): every implementation sub-task is preceded by a testsuite sub-task that lands failing (RED) tests first, then implements to GREEN. The deterministic harness (Phase 1) is the RED infrastructure that pins every later fix to a walcompare/invariant violation. No (P) markers: Phases 2–6 modify shared files (ha.c, persist.c, config_repl.c) and the RED cases share test_ha_core_safety.c, so the plan is sequential — concurrent edits would contend (same constraint as ha-convergence-recovery). Foundation Phase 1 establishes shared prerequisites and is also sequential. Correctness oracle: verify every change against raft/raft.tla and the invariant checklist in src/controller/CLAUDE.md (Election Safety, Leader Completeness, State Machine Safety, Commit Ordering/Durability). Verify anchors before editing (files drift): the design and research.md carry 2026-06-27 file:line anchors; re-grep before each edit. Root cause (task 1.3, DONE + verified): the term-blind hypothesis is refuted. The real defect is cross-term catch-up payload loss — ha_stream_wal_to_standby silently ships PLEN=0 on a short pread/malloc-fail, and the (term,lsn)-only persist guard is payload-blind. Phase 2 targets the streamer + payload-aware guard (research.md §"Task 1.3"). A green synthetic unit test over a still-red soak does not satisfy 1.1/8.1 — closure requires the real-fs chaotic soak (7.2) clean.

• 1. Foundation: deterministic chaotic harness and live-divergence reproduction

• 1.1 Extend the divergence detector to a machine-checkable per-member report

  • Extend walcompare to emit a parseable per-member (lsn -> term, payload-crc, present/MISSING) report over the committed prefix, and classify each divergence as committed vs uncommitted
  • Observable completion: walcompare prints a parseable per-member report and a committed-vs-uncommitted classification; the existing soak still detects the round-3 LSN divergence through it
  • Requirements: 7.1, 7.5
  • Boundary: Deterministic Chaotic Harness

• 1.2 Add a chaotic soak mode with an isolated verdict

  • Add an overlapping-kill mode to the soak driver (kills landing inside election windows, not only sequential kill→wait→rejoin); produce a verdict that counts walcompare divergences and committed-job loss while excluding client-discovery (bug-854) and overlayfs fdatasync (bug-924) failures from the divergence/job-loss result
  • Observable completion: the soak runs chaotic mode against real-fs release binaries and emits a verdict whose divergence/job-loss counts are unaffected by bug-854/bug-924
  • Requirements: 7.5, 8.4
  • Boundary: Acceptance Soak Gate, Deterministic Chaotic Harness

• 1.3 Reproduce and classify the live divergence, then bisect to a seam

  • Run the chaotic soak to capture the actual walcompare committed-prefix divergence (RED), classify it via (term, lsn, pcrc) (which member, which term, committed vs uncommitted), and bisect it to the concrete ingest path; confirm or refute the term-blind-bypass hypothesis
  • Observable completion: a recorded RED divergence with member/term/lsn classification and the identified seam, written to research.md; the hypothesis is confirmed or a new trigger is named before any fix
  • Requirements: 7.1, 1.1
  • Boundary: Deterministic Chaotic Harness

• 1.4 Stand up the unit/integration harness infrastructure

  • Create test_ha_core_safety.c with the deterministic gate/probe seams (no sleeps; teardown drains pending delaymgr tasks to avoid the bug-1224 teardown-race UAF), the (term, lsn)/apply-gap/kill-injection fixtures, and register it in the controller unit-test build; include one smoke-RED case proving the harness can observe a divergence. The per-defect RED bodies are owned by their phases (2.3 ingest, 4.1 reconvergence, 5.1 election) — this task provides the shared seams they build on, not those cases
  • Observable completion: test_ha_core_safety builds and runs, the injection fixtures and probe seams are usable by later phases, and the smoke-RED case FAILs on the baseline with no ASAN teardown errors
  • Requirements: 7.1, 7.4
  • Boundary: Deterministic Chaotic Harness

• 1.5 Make soak primary-detection robust to the release-build log buffer

  • Task 1.3 found the release build block-buffers its --logfile and flushes only on signal, so the soak's log-grep primary/convergence detection cannot see an elected primary and false-aborts. Switch the soak's primary + convergence detection to a client probe (ctrlstatus/xce_test) instead of log-grep, so the chaotic soak runs unattended on release binaries. (Only if a client probe is insufficient, fall back to a controller release log-flush change that does not alter production logging semantics.)
  • Observable completion: run-ha-soak.sh --chaotic on the ~/tmp real-fs path with the src/build.release binaries detects the elected primary each round via the client probe and no longer false-aborts on "no primary within Ns"; a short (2-round) run reaches its verdict line
  • Requirements: 7.5, 8.3
  • Boundary: Acceptance Soak Gate, Deterministic Chaotic Harness
  • Depends: 1.2

• 2. Committed-prefix divergence fix: cross-term catch-up payload integrity + payload-aware guard

  • Root cause (task 1.3, verified): the cross-term catch-up streamer silently ships PLEN=0 on a short pread/malloc-fail, and the (term,lsn)-only persist guard is payload-blind. Term and ingest-path are correct — the payload is lost.

• 2.1 RED: payload-aware persistence guard tests

  • Add cases: an empty-payload (PLEN=0) entry written at an existing LSN N followed by the correct full-payload entry must end with the FULL payload (today the (term,lsn)-only idempotency guard silently no-ops the corrective write); the reverse (full then empty at the same (term,lsn)) must NOT degrade the stored entry to empty; an identical (term, payload-crc) re-write is a safe idempotent no-op
  • Observable completion: the new persistence cases FAIL on the baseline because the guard compares only (term, lsn) and cannot see the payload difference
  • Requirements: 1.1, 1.2, 2.1, 2.2, 3.1, 3.4
  • Boundary: Persist Conflict Guard

• 2.2 Make the persistence guard (term, lsn, payload-crc)-aware

  • Extend the LSN-only idempotency check (persist.c:822): identical (term, payload-crc) at an LSN is an idempotent no-op; a differing payload-crc (or term) at an existing LSN is surfaced for repair, never a silent return 0; never accept a PLEN=0 write as the durable form of a known-non-empty entry; preserve persist-before-ACK, the term index, and WAL_LEGACY_TERM
  • Observable completion: the 2.1 cases pass; an empty-over-real write at an existing committed LSN no longer silently survives; identical re-writes stay idempotent
  • Requirements: 1.1, 1.2, 2.1, 2.2, 2.4, 3.1
  • Boundary: Persist Conflict Guard

• 2.3 RED: cross-term catch-up streamer payload-integrity tests

  • Add a case reproducing the live signature: a cross-term catch-up (stored term < leader current term, bug-1067 path) whose entry-body pread returns short / malloc fails must NOT result in a persisted PLEN=0 entry at a committed LSN — instead the stream must error and retry. Also add the defensive case that a term==0-shaped catch-up entry routes through the reconcile seam (no direct-persist bypass), and the unrecoverable-fence case (a node that cannot obtain the majority-agreed committed prefix refuses promotion instead of serving divergent state). Instrument payload_len at send and at on_persist_entry to disambiguate send-side-empty vs transitive-empty propagation
  • Observable completion: the streamer case FAILs on the baseline because the short-read/malloc-fail path silently ships PLEN=0; the seam-routing and fence cases FAIL because those paths/fence do not exist yet
  • Requirements: 1.1, 1.2, 2.1, 3.1, 3.2, 3.3, 7.1
  • Boundary: Catch-up Payload Integrity, Unified Entry Ingest
  • Depends: 2.2

• 2.4 Fix the streamer payload integrity + defensive seam routing + fence

  • Core: in ha_stream_wal_to_standby (config_repl.c ~2154-2163), fail loud on a short pread/malloc-fail with a bounded retry instead of freeing the buffer and shipping PLEN=0; a non-empty entry is never transmitted empty. Disambiguate and handle send-side-empty vs transitive-empty propagation per the 2.3 instrumentation. Defensive: retire the term-blind ha_apply_single_entry direct-persist branch so all ingest routes through the seam; surface genuinely-unrecoverable divergence as a loud non-promotable fence (never self-terminate); defer file I/O to delaymgr (never the callback/iomgr thread)
  • Observable completion: 2.3 passes (streamer never ships empty; seam-routing and fence cases green); on the 1.3 reproduction path (real-fs release chaotic soak) walcompare reports zero committed divergence at the previously-divergent LSNs
  • Requirements: 1.1, 1.2, 1.3, 2.1, 2.3, 3.1, 3.2, 3.3, 3.4
  • Boundary: Catch-up Payload Integrity, Unified Entry Ingest
  • Depends: 2.2, 2.3

• 3. Snapshot-boundary reconciliation

• 3.1 RED: snapshot post-install reconcile test

  • Add a case where a divergent pre-snapshot entry must be reconciled against the installed checkpoint's (term, lsn) boundary (today snapshot install sets applied-lsn without a (term, lsn) reconcile)
  • Observable completion: the case FAILS on the baseline because no (term, lsn) reconcile occurs at the snapshot boundary
  • Requirements: 3.1, 5.1
  • Boundary: Snapshot Boundary Reconcile

• 3.2 Establish the snapshot (term, lsn) boundary

  • Make snapshot install establish a verifiable (term, lsn) at the checkpoint so post-install AE intake reconciles correctly and no committed entry below the checkpoint can diverge
  • Observable completion: 3.1 passes; a member that installed a snapshot matches the leader's (term, payload-crc) at and below the checkpoint boundary
  • Requirements: 3.1, 5.1
  • Boundary: Snapshot Boundary Reconcile
  • Depends: 2.4

• 4. Standby reconvergence completeness

• 4.1 RED: reconvergence-gate test

  • Add a case where a rejoining node with an injected catch-up apply gap must not be reported converged/healthy until applied_lsn and log_len equal the leader's committed boundary (today the node is healthy at match-index alone)
  • Observable completion: the case FAILS on the baseline because convergence is reported before applied-state agreement
  • Requirements: 5.1, 5.2, 5.3, 5.4, 7.2
  • Boundary: Standby Reconvergence

• 4.2 Gate healthy/3-of-3 on committed-and-applied agreement

  • Synchronize post-recovery log_len/applied-lsn and complete outstanding catch-up apply (routed through the seam, reusing the rejoin intake hook) before reporting a node converged; bound the recovery window
  • Observable completion: 4.1 passes; a rejoining node reports converged only after applied_lsn == log_len == leader committed, restoring a healthy 3-of-3
  • Requirements: 5.1, 5.2, 5.3, 5.4
  • Boundary: Standby Reconvergence
  • Depends: 2.4

• 5. Election liveness and safety under churn

• 5.1 RED: election liveness and Election Safety tests

  • Add cases: repeated rapid kill/restart rounds must yield a higher-term primary each round; a scripted failed election round must be followed by another election; across overlapping kills, at most one member ever reaches committing-primary per term (Election Safety, mapped to raft/raft.tla)
  • Observable completion: the liveness cases FAIL on the baseline (round-N stall); the Election Safety assertion runs and reports per-term primary counts
  • Requirements: 4.1, 4.3, 6.1, 6.2, 6.3, 7.3
  • Boundary: Election Liveness

• 5.2 Guarantee election completion without losing single-leader safety

  • Ensure a failed election round triggers a further election (no permanent stall while quorum is reachable); pair step-down-on-higher-term with election restart; preserve at-most-one-committing-primary-per-term
  • Observable completion: 5.1 liveness cases pass with no permanent stall across rapid rounds; the Election Safety assertion still holds (no two committing primaries in a term)
  • Requirements: 4.1, 4.2, 4.3, 6.1, 6.2, 6.3
  • Boundary: Election Liveness

• 6. Integration: single-seam invariant end-to-end

• 6.1 Verify leader→standby replication carries (term, payload) faithfully end-to-end

  • Integration check that the live leader replication AND the cross-term catch-up streaming path transmit each entry's full (term, payload) to the receiver: no term==0 on the wire from a live leader (defensive), and — the real concern — no non-empty entry ever arrives with PLEN=0; the walAck catch-up continuation feeds only the seam ingest path
  • Observable completion: an end-to-end test (or instrumented soak round) shows leader and standby hold identical (term, payload-crc) for every replicated and cross-term-caught-up LSN; walcompare --report clean across members
  • Requirements: 2.1, 2.3, 3.2
  • Boundary: Catch-up Payload Integrity, Unified Entry Ingest
  • Depends: 2.4

• 6.2 Verify the single-seam invariant and restart identity

  • Assert no ingest path (live replication, catch-up batch, snapshot post-install, rejoin) writes the WAL outside the reconcile seam, and that each entry's (term, lsn) identity survives a restart/recovery
  • Observable completion: an integration test confirms every ingest path reconciles through the seam and that entry terms are preserved across restart; no direct-persist bypass remains
  • Requirements: 1.1, 1.2, 2.4, 3.1
  • Depends: 2.4, 3.2, 4.2

• 7. Validation: regression and acceptance soak gate

• 7.1 Full controller suite under ASAN with the new harness green

  • Build and run the full controller unit suite under ASAN (suite-by-suite if the aggregate hits the known 300s cap); fix any regression from the ingest/persist/election changes
  • Observable completion: the full suite is green under ASAN and every test_ha_core_safety case passes with no ASAN errors
  • Requirements: 7.4
  • Depends: 6.2, 5.2

• 7.2 Acceptance chaotic-failover soak gate

  • Run the chaotic soak (≥6 rounds, overlapping kills) against real-fs release binaries and assert zero walcompare divergence, zero committed-job loss, and 3-of-3 reconvergence plus a new primary after every kill round, with bug-854/bug-924 isolated from the verdict
  • Observable completion: the soak exits PASS over ≥6 chaotic rounds with zero divergence and zero job loss — the green result that gates the raft-drive-async production flag-flip
  • Requirements: 1.4, 7.4, 8.1, 8.2, 8.3, 8.4
  • Depends: 1.5, 6.2, 5.2

• 7.3 Hypothesis-validation closeout

  • Confirm the live soak divergence is eliminated by the implemented fixes (not by synthetic unit tests alone); if any residual divergence remains, classify it via walcompare (term, lsn, pcrc), record the new finding in research.md, and add a follow-up fix task rather than declaring closure
  • Observable completion: the soak divergence count is zero with closure justified by the live soak, OR a recorded new finding plus a follow-up task; raft/raft.tla invariants (Election Safety, Leader Completeness, State Machine Safety, Commit Ordering) reviewed against the final behavior
  • Requirements: 1.1, 1.4, 7.1, 8.1
  • Depends: 7.2