Cluster Allocation Explain API

原文链接 : https://www.elastic.co/guide/en/elasticsearch/reference/5.0/cluster-allocation-explain.html

译文链接 : http://www.apache.wiki/display/Elasticsearch/Cluster+Allocation+Explain+API

贡献者 : 那伊抹微笑

cluster allocation explanation API 的目的是帮助回答这个问题 “为什么这个分片没有被分配”。为了说明分片的分配（未分配状态），发出一个这样的请求 : 

  1. $ curl -XGET 'http://localhost:9200/_cluster/allocation/explain' -d'{
  2.   "index": "myindex",
  3.   "shard": 0,
  4.   "primary": false
  5. }'

指定您希望查看的说明的 index 和 shard 的 id，和 primary 标记一样来指出是否 explain 一个主或者副本分片。

该响应如下 : 

  1. {
  2.   "shard" : {
  3.     "index" : "myindex",
  4.     "index_uuid" : "KnW0-zELRs6PK84l0r38ZA",
  5.     "id" : 0,
  6.     "primary" : false
  7.   },
  8.   "assigned" : false,                             ①
  9.   "shard_state_fetch_pending": false,             ②
  10.   "unassigned_info" : {
  11.     "reason" : "INDEX_CREATED",                   ③
  12.     "at" : "2016-03-22T20:04:23.620Z"
  13.   },
  14.   "allocation_delay_ms" : 0,                      ④
  15.   "remaining_delay_ms" : 0,                       ⑤
  16.   "nodes" : {
  17.     "V-Spi0AyRZ6ZvKbaI3691w" : {
  18.       "node_name" : "H5dfFeA",
  19.       "node_attributes" : {                       ⑥
  20.         "bar" : "baz"
  21.       },
  22.       "store" : {
  23.         "shard_copy" : "NONE"                     ⑦
  24.       },
  25.       "final_decision" : "NO",                    ⑧
  26.       "final_explanation" : "the shard cannot be assigned because one or more allocation decider returns a 'NO' decision",
  27.       "weight" : 0.06666675,                      ⑨
  28.       "decisions" : [ {                           ⑩
  29.         "decider" : "filter",
  30.         "decision" : "NO",
  31.         "explanation" : "node does not match index include filters [foo:\"bar\"]"
  32.       } ]
  33.     },
  34.     "Qc6VL8c5RWaw1qXZ0Rg57g" : {
  35.       "node_name" : "bGG90GE",
  36.       "node_attributes" : {
  37.         "bar" : "baz",
  38.         "foo" : "bar"
  39.       },
  40.       "store" : {
  41.         "shard_copy" : "AVAILABLE"
  42.       },
  43.       "final_decision" : "NO",
  44.       "final_explanation" : "the shard cannot be assigned because one or more allocation decider returns a 'NO' decision",
  45.       "weight" : -1.3833332,
  46.       "decisions" : [ {
  47.         "decider" : "same_shard",
  48.         "decision" : "NO",
  49.         "explanation" : "the shard cannot be allocated on the same node id [Qc6VL8c5RWaw1qXZ0Rg57g] on which it already exists"
  50.       } ]
  51.     },
  52.     "PzdyMZGXQdGhqTJHF_hGgA" : {
  53.       "node_name" : "DKDM97B",
  54.       "node_attributes" : { },
  55.       "store" : {
  56.         "shard_copy" : "NONE"
  57.       },
  58.       "final_decision" : "NO",
  59.       "final_explanation" : "the shard cannot be assigned because one or more allocation decider returns a 'NO' decision",
  60.       "weight" : 2.3166666,
  61.       "decisions" : [ {
  62.         "decider" : "filter",
  63.         "decision" : "NO",
  64.         "explanation" : "node does not match index include filters [foo:\"bar\"]"
  65.       } ]
  66.     }
  67.   }
  68. }
编号 描述
Cluster Allocation Explain API - 图1 Whether the shard is assigned or unassigned
Cluster Allocation Explain API - 图2 Whether information about the shard is still being fetched
Cluster Allocation Explain API - 图3 Reason for the shard originally becoming unassigned
Cluster Allocation Explain API - 图4 Configured delay before the shard can be allocated
Cluster Allocation Explain API - 图5 Remaining delay before the shard can be allocated
Cluster Allocation Explain API - 图6 User-added attributes the node has
Cluster Allocation Explain API - 图7 The shard copy information for this node and error (if applicable)
Cluster Allocation Explain API - 图8 Final decision and explanation of whether the shard can be allocated to this node
Cluster Allocation Explain API - 图9 Weight for how much the allocator would like to allocate the shard to this node
Cluster Allocation Explain API - 图10 List of node decisions factoring into final decision about the shard

对于一个已经分配的分片来说，输出与下面相似 : 

  1. {
  2.   "shard" : {
  3.     "index" : "only-foo",
  4.     "index_uuid" : "KnW0-zELRs6PK84l0r38ZA",
  5.     "id" : 0,
  6.     "primary" : true
  7.   },
  8.   "assigned" : true,
  9.   "assigned_node_id" : "Qc6VL8c5RWaw1qXZ0Rg57g",      ①
  10.   "shard_state_fetch_pending": false,
  11.   "allocation_delay_ms" : 0,
  12.   "remaining_delay_ms" : 0,
  13.   "nodes" : {
  14.     "V-Spi0AyRZ6ZvKbaI3691w" : {
  15.       "node_name" : "bGG90GE",
  16.       "node_attributes" : {
  17.         "bar" : "baz"
  18.       },
  19.       "store" : {
  20.         "shard_copy" : "NONE"
  21.       },
  22.       "final_decision" : "NO",
  23.       "final_explanation" : "the shard cannot be assigned because one or more allocation decider returns a 'NO' decision",
  24.       "weight" : 1.4499999,
  25.       "decisions" : [ {
  26.         "decider" : "filter",
  27.         "decision" : "NO",
  28.         "explanation" : "node does not match index include filters [foo:\"bar\"]"
  29.       } ]
  30.     },
  31.     "Qc6VL8c5RWaw1qXZ0Rg57g" : {
  32.       "node_name" : "I8hydUG",
  33.       "node_attributes" : {
  34.         "bar" : "baz",
  35.         "foo" : "bar"
  36.       },
  37.       "store" : {
  38.         "shard_copy" : "AVAILABLE"
  39.       },
  40.       "final_decision" : "ALREADY_ASSIGNED",        ②
  41.       "final_explanation" : "the shard is already assigned to this node",
  42.       "weight" : 0.0,
  43.       "decisions" : [ {
  44.         "decider" : "same_shard",
  45.         "decision" : "NO",
  46.         "explanation" : "the shard cannot be allocated on the same node id [Qc6VL8c5RWaw1qXZ0Rg57g] on which it already exists"
  47.       } ]
  48.     },
  49.     "PzdyMZGXQdGhqTJHF_hGgA" : {
  50.       "node_name" : "H5dfFeA",
  51.       "node_attributes" : { },
  52.       "store" : {
  53.         "shard_copy" : "NONE"
  54.       },
  55.       "final_decision" : "NO",
  56.       "final_explanation" : "the shard cannot be assigned because one or more allocation decider returns a 'NO' decision",
  57.       "weight" : 3.6999998,
  58.       "decisions" : [ {
  59.         "decider" : "filter",
  60.         "decision" : "NO",
  61.         "explanation" : "node does not match index include filters [foo:\"bar\"]"
  62.       } ]
  63.     }
  64.   }
  65. }
编号 描述
Cluster Allocation Explain API - 图11 Node the shard is currently assigned to
Cluster Allocation Explain API - 图12 The decision is “ALREADY_ASSIGNED” because the shard is currently assigned to this node

您也可以让 Elasticsearch explain 第一个未分配分片的分配情况，它可以通过发送一个空的 body 来找到，例如 : 

  1. $ curl -XGET 'http://localhost:9200/_cluster/allocation/explain'

如果您想要去包含所有的那些我们考虑到的最终的决策的决定，该 include_yes_decisions 参数将返回所有的决策 : 

  1. $ curl -XGET 'http://localhost:9200/_cluster/allocation/explain?include_yes_decisions=true'

此外，通过设置 include_disk_info参数为 true，您可以返回通过集群信息服务返回收集到的信息，包括硬盘使用和分配大小。

  1. $ curl -XGET 'http://localhost:9200/_cluster/allocation/explain?include_disk_info=true'