{
  "id": "redis/stream-entries-added-to-consumer-group-pel",
  "signature": "Error: Stream entries added to consumer group PEL without acknowledgment",
  "signature_zh": "错误：流条目已添加到消费者组待处理条目列表但未确认",
  "regex": "Stream entries added to consumer group PEL without acknowledgment",
  "domain": "redis",
  "category": "data_error",
  "subcategory": null,
  "root_cause": "Consumer group pending entries list (PEL) grows unbounded as consumers fail to acknowledge processed messages, potentially causing memory exhaustion and performance degradation.",
  "root_cause_type": "generic",
  "root_cause_zh": "消费者组待处理条目列表(PEL)因消费者未能确认已处理的消息而无限制增长，可能导致内存耗尽和性能下降。",
  "versions": [
    {
      "version": "redis 6.2",
      "introduced": null,
      "deprecated": null,
      "removed": null,
      "behavior_change": null,
      "status": "active"
    },
    {
      "version": "redis 7.0",
      "introduced": null,
      "deprecated": null,
      "removed": null,
      "behavior_change": null,
      "status": "active"
    },
    {
      "version": "redis 7.2",
      "introduced": null,
      "deprecated": null,
      "removed": null,
      "behavior_change": null,
      "status": "active"
    }
  ],
  "os_specific": {},
  "dead_ends": [
    {
      "action": "Increasing consumer group size to handle more messages",
      "why_fails": "Adding more consumers does not clear the PEL; each consumer still accumulates unacknowledged entries, worsening the issue.",
      "fail_rate": 0.85,
      "condition": "",
      "sources": []
    },
    {
      "action": "Deleting and recreating the stream",
      "why_fails": "Deletes all data and disrupts active consumers; PEL rebuilds quickly if root cause (lack of acknowledgment) persists.",
      "fail_rate": 0.9,
      "condition": "",
      "sources": []
    },
    {
      "action": "Setting XREADGROUP COUNT to a very high value",
      "why_fails": "High COUNT does not clear PEL; it only returns more entries, and unacknowledged entries remain, continuing to grow the PEL.",
      "fail_rate": 0.8,
      "condition": "",
      "sources": []
    }
  ],
  "workarounds": [
    {
      "action": "Periodically acknowledge processed entries using XACK: `XACK mystream mygroup 1526569498055-0` for each message ID. Automate with a background job that calls XACK after successful processing.",
      "success_rate": 0.9,
      "how": "Periodically acknowledge processed entries using XACK: `XACK mystream mygroup 1526569498055-0` for each message ID. Automate with a background job that calls XACK after successful processing.",
      "condition": "",
      "sources": []
    },
    {
      "action": "Set a consumer group PEL size limit with `XGROUP SETID mystream mygroup $` and use XTRIM to cap stream length: `XTRIM mystream MAXLEN ~ 10000`.",
      "success_rate": 0.85,
      "how": "Set a consumer group PEL size limit with `XGROUP SETID mystream mygroup $` and use XTRIM to cap stream length: `XTRIM mystream MAXLEN ~ 10000`.",
      "condition": "",
      "sources": []
    },
    {
      "action": "Use XAUTOCLAIM to reassign idle PEL entries to other consumers: `XAUTOCLAIM mystream mygroup consumer2 3600000 0-0` after setting a reasonable idle timeout.",
      "success_rate": 0.8,
      "how": "Use XAUTOCLAIM to reassign idle PEL entries to other consumers: `XAUTOCLAIM mystream mygroup consumer2 3600000 0-0` after setting a reasonable idle timeout.",
      "condition": "",
      "sources": []
    }
  ],
  "workarounds_zh": [
    "Periodically acknowledge processed entries using XACK: `XACK mystream mygroup 1526569498055-0` for each message ID. Automate with a background job that calls XACK after successful processing.",
    "Set a consumer group PEL size limit with `XGROUP SETID mystream mygroup $` and use XTRIM to cap stream length: `XTRIM mystream MAXLEN ~ 10000`.",
    "Use XAUTOCLAIM to reassign idle PEL entries to other consumers: `XAUTOCLAIM mystream mygroup consumer2 3600000 0-0` after setting a reasonable idle timeout."
  ],
  "transition_graph": {
    "leads_to": [],
    "preceded_by": [],
    "frequently_confused_with": []
  },
  "official_doc_url": "https://redis.io/docs/latest/commands/xack/",
  "official_doc_section": null,
  "error_code": "ERR",
  "verification_tier": "ai_generated",
  "confidence": 0.85,
  "fix_success_rate": 0.85,
  "resolvable": "true",
  "first_seen": "2024-03-15",
  "last_confirmed": "2024-06-01",
  "last_updated": "2024-06-01",
  "evidence_count": 1,
  "tags": [],
  "locale": "en",
  "aliases": []
}