{
  "id": "elasticsearch/field-cache-merge-contention",
  "signature": "ElasticsearchException: field cache merge contention detected on index [my_index], shard [0], segment [_a1b2c3]",
  "signature_zh": "Elasticsearch异常：索引 [my_index] 分片 [0] 段 [_a1b2c3] 检测到字段缓存合并争用",
  "regex": "ElasticsearchException: field cache merge contention detected on index \\[.*?\\], shard \\[\\d+\\], segment \\[.*?\\]",
  "domain": "elasticsearch",
  "category": "runtime_error",
  "subcategory": null,
  "root_cause": "Concurrent segment merges trigger field cache rebuilds, causing contention and increased latency when multiple merges try to update the same cache entries.",
  "root_cause_type": "generic",
  "root_cause_zh": "并发段合并触发字段缓存重建，当多个合并尝试更新相同缓存条目时，导致争用和延迟增加。",
  "versions": [
    {
      "version": "7.17.0",
      "introduced": null,
      "deprecated": null,
      "removed": null,
      "behavior_change": null,
      "status": "active"
    },
    {
      "version": "8.11.0",
      "introduced": null,
      "deprecated": null,
      "removed": null,
      "behavior_change": null,
      "status": "active"
    },
    {
      "version": "8.12.0",
      "introduced": null,
      "deprecated": null,
      "removed": null,
      "behavior_change": null,
      "status": "active"
    }
  ],
  "os_specific": {},
  "dead_ends": [
    {
      "action": "",
      "why_fails": "Reduces merge concurrency but increases merge time and can lead to too many segments, degrading search performance.",
      "fail_rate": 0.8,
      "condition": "",
      "sources": []
    },
    {
      "action": "",
      "why_fails": "Larger cache delays contention but doesn't prevent it; high memory usage may cause OOM.",
      "fail_rate": 0.7,
      "condition": "",
      "sources": []
    }
  ],
  "workarounds": [
    {
      "action": "Reduce merge concurrency by setting `index.merge.scheduler.max_thread_count: 2` and `index.merge.scheduler.max_merge_count: 6`.",
      "success_rate": 0.8,
      "how": "Reduce merge concurrency by setting `index.merge.scheduler.max_thread_count: 2` and `index.merge.scheduler.max_merge_count: 6`.",
      "condition": "",
      "sources": []
    },
    {
      "action": "Use `indices.fielddata.cache.expire: 30m` to clear field cache periodically, reducing contention windows.",
      "success_rate": 0.75,
      "how": "Use `indices.fielddata.cache.expire: 30m` to clear field cache periodically, reducing contention windows.",
      "condition": "",
      "sources": []
    },
    {
      "action": "Force merge indices during maintenance windows: `POST my_index/_forcemerge?max_num_segments=1`.",
      "success_rate": 0.9,
      "how": "Force merge indices during maintenance windows: `POST my_index/_forcemerge?max_num_segments=1`.",
      "condition": "",
      "sources": []
    }
  ],
  "workarounds_zh": [
    "Reduce merge concurrency by setting `index.merge.scheduler.max_thread_count: 2` and `index.merge.scheduler.max_merge_count: 6`.",
    "Use `indices.fielddata.cache.expire: 30m` to clear field cache periodically, reducing contention windows.",
    "Force merge indices during maintenance windows: `POST my_index/_forcemerge?max_num_segments=1`."
  ],
  "transition_graph": {
    "leads_to": [],
    "preceded_by": [],
    "frequently_confused_with": []
  },
  "official_doc_url": "https://www.elastic.co/guide/en/elasticsearch/reference/current/field-cache.html",
  "official_doc_section": null,
  "error_code": "ES_FIELD_CACHE_MERGE_CONTENTION",
  "verification_tier": "ai_generated",
  "confidence": 0.85,
  "fix_success_rate": 0.82,
  "resolvable": "partial",
  "first_seen": "2025-01-20",
  "last_confirmed": "2024-06-01",
  "last_updated": "2024-06-01",
  "evidence_count": 1,
  "tags": [],
  "locale": "en",
  "aliases": []
}