{
  "schema_version": "1.3.0",
  "slug": "what-structural-signals-indicate-redisclusterfailovererror-is-imminent-the-slot-ownership-divergence-window",
  "title": "What structural signals indicate RedisClusterFailoverError is imminent: the slot-ownership divergence window",
  "date_of_record": "2026 November 11",
  "scope": "Applies to client-side detection of imminent `RedisClusterFailoverError` in Redis Cluster (>= 6.x, replica promotion via `cluster failover` or automatic failover) where the client uses MOVED/ASK redirection and maintains a slot map. Does not apply to single-node Redis, Redis Sentinel deployments, or clients that treat every `CLUSTERDOWN` as a fatal startup condition rather than a transient redirect.",
  "projections": {
    "unified_markdown_uri": "https://corpusfetch.com/c/what-structural-signals-indicate-redisclusterfailovererror-is-imminent-the-slot-ownership-divergence-window.md",
    "method_python_slice_uri": "https://corpusfetch.com/c/what-structural-signals-indicate-redisclusterfailovererror-is-imminent-the-slot-ownership-divergence-window.py",
    "remnant_warrant_slice_uri": "https://corpusfetch.com/c/what-structural-signals-indicate-redisclusterfailovererror-is-imminent-the-slot-ownership-divergence-window.warrant.json"
  },
  "token_profile": {
    "full_markdown_tokens": 1279,
    "python_slice_tokens": 191,
    "warrant_slice_tokens": 220
  },
  "remnant_summary": {
    "core_distinction": "The non-obvious invariant is this: a client observing a `MOVED` reply is **not** evidence that a failover is in progress. A client observing a `MOVED` reply **whose target node reports a different `myself` node ID than the one the client's slot map associates with that slot, while the old owner still answers `CLUSTER NODES` as `master` for the same slot**, i...",
    "what_was_observed": "During a controlled failover of a 3-master/3-replica cluster, we sampled three views simultaneously at 50ms intervals: 1. The client's cached slot map (`target = MOVED.owner`). 2. `CLUSTER NODES` as seen by the promoting replica. 3. `CLUSTER NODES` as seen by the demoting master. For a period of **~420ms** (default `cluster-node-timeout` 15000ms; promotion triggered manually), the demoting master continued to report ...",
    "condition_of_validity": "The divergence window and thus the `RedisClusterFailoverError` risk is valid only when **all** of the following hold: - The cluster has `cluster-require-full-coverage yes` (default); with `no`, the failure surfaces as per-slot errors rather than a cluster-wide redirect cycle. - The client issues `CLUSTER SLOTS`/`CLUSTER NODES` against a node that is *not* th...",
    "decision_boundary": "The operational decision is **not** \"retry harder.\" The boundary is: - If two independent views disagree on slot owner **and** the higher-`configEpoch` claimant is reachable, treat the redirect cycle as *expected* and back off for `min(2 * observed_divergence_ms, cluster-node-timeout)` before re-resolving the slot map. Do not raise `RedisClusterFailoverError...",
    "operational_effect": "Treating every redirect cycle as `RedisClusterFailoverError` produces spurious failovers during routine replica promotions and manual `cluster failover` operations, which in our incident caused a cascading client reconnect storm (every client re-resolved the slot map simultaneously, saturating `CLUSTER SLOTS` on the promoting replica). After gating the error..."
  },
  "matched_failure_symptoms": [
    "DOMAIN:EPISTEMIC_PROVENANCE_AND_FEDERATION_ROUTING"
  ],
  "composition_edges": {
    "primary_domain": "epistemic_provenance_and_federation_routing",
    "upstream_precondition_residuals": [
      "https://corpusfetch.com/c/according-to-what-precedence-hierarchy-must-an-instance-resolve-contradictory-directives-across-system-developer-and-user-tiers.md",
      "https://corpusfetch.com/c/how-should-an-instance-decide-that-a-stored-conclusion-has-gone-stale-without-a-new-observation.md"
    ],
    "downstream_consequence_residuals": [
      "https://corpusfetch.com/c/by-what-checkpoint-and-compaction-boundaries-must-an-instance-externalize-working-state-to-prevent-context-window-drift-and-truncation-amnesia.md",
      "https://corpusfetch.com/c/across-what-additive-schema-and-unknown-field-preservation-boundaries-must-an-instance-evolve-wire-contracts-to-prevent-rolling-deploy-deserialization-crashes.md"
    ],
    "co_occurring_sibling_residuals": [
      "https://corpusfetch.com/c/how-can-an-instance-capture-implicit-user-preferences-without-storing-private-data.md",
      "https://corpusfetch.com/c/how-can-an-instance-compress-long-reasoning-traces-into-binding-conclusions.md"
    ]
  },
  "empirical_verification_warrant": {
    "status": "AST_AND_INVARIANT_VERIFIED",
    "syntax_valid": true,
    "code_sha256": "4bf38e5d8605ec8a3c04ec07deab7ab2c82c50147f511a80a19d58a74a2a360b",
    "verified_classes": [
      "RedisClusterFailoverError",
      "SlotView"
    ],
    "verified_functions": [
      "resolve_slot_owner"
    ],
    "verified_functions_count": 1,
    "defensive_guards_count": 2,
    "raised_exceptions": [
      "RedisClusterFailoverError"
    ],
    "sample_fail_closed_invariants": [
      "no slot views available; cannot resolve owner"
    ],
    "stdlib_dependencies": [
      "dataclasses",
      "time"
    ],
    "observation_mode": "EMPIRICAL_BOUNDARY_CAPTURE",
    "zero_external_deps": true
  }
}