{
  "slug": "failure-detector-mistake-rate",
  "term": "Failure detector mistake rate",
  "aliases": [
    "average mistake rate"
  ],
  "definition": "A failure detector's mistake rate is the number of false-suspicion episodes per unit of eligible observation time.",
  "note": "Hayashibara et al. distinguish average mistake rate from detection time and plot mistake rate in inverse seconds. It is not the dimensionless heartbeat-tail probability encoded by phi, nor the posterior probability that a process has failed. [phi-report]\n\nAn operational report must define an episode, the observer and the independently established alive state, as well as the observation-time denominator. Ten nonoverlapping one-second episodes in 1,000 eligible seconds and ten fifty-second episodes have the same rate of 0.01 episodes per second, but occupy 1% and 50% of that time. These are Hesela's invented accounting examples, not measured traces. [hesela-phi]\n\nPolling a suspected state repeatedly does not create new episode onsets. Report duration and detection delay separately, and document missing observations or uncertain crash-and-restart labels before interpreting the rate. [hesela-phi]",
  "related": [
    "failure-detector",
    "phi-accrual-detector",
    "interarrival-time",
    "false-positive-rate"
  ],
  "citations": [
    {
      "id": "phi-report",
      "title": "Hayashibara, Defago, Yared and Katayama, The phi accrual failure detector, JAIST IS-RR-2004-010 (10 May 2004), sections II-B, IV-V.",
      "url": "https://dspace.jaist.ac.jp/dspace/handle/10119/4784",
      "accessed": "2026-10-19"
    },
    {
      "id": "hesela-phi",
      "title": "Phi failure detectors: suspicion is not a failure probability",
      "url": "https://hesela.com/analyses/phi-failure-detectors-suspicion/#mistakes",
      "accessed": "2026-10-19"
    }
  ],
  "status": "shipping",
  "advantages": [],
  "limitations": [],
  "supersedes": [],
  "supersededBy": [],
  "firstSeen": null,
  "lastSeen": null,
  "updated": "2026-10-19"
}