执行命令update-by-query报错“Trying to create too many scroll contexts”

问题现象

云搜索服务的Elasticsearch集群执行命令update-by-query，出现报错“Trying to create too many scroll contexts.” ，具体报错信息如下：

{"error":{"root_cause":[{"type":"exception","reason":"Trying to create too many scroll contexts. Must be less than or equal to: [100000]. This limit can be set by changing the [search.max_open_scroll_context] setting."},{"type":"exception","reason":"Trying to create too many scroll contexts. Must be less than or equal to: [100000]. ......

原因分析

当集群每调用一次scroll的创建接口，都会新建一个scroll使用的context，当scroll contexts的数目达到预定值时，将无法继续创建scroll。

处理步骤

GET /_nodes/stats/indices/search

当数目达到最大值时，可以通过以下两种方式解决。

• 方式一：删除无用的scroll，释放scroll contexts的存储空间。

  DELETE /_search/scroll
  {  "scroll_id" : "DXF1ZXJ5QW5kRmV0Y2gBAAAAAAAAAD4WYm9laVYtZndUQlNsdDcwakFMNjU1QQ=="}

• 方式二：调整“search.max_open_scroll_context”的值，增加scroll contexts的存储空间。

  PUT /_cluster/settings
  {
  	"persistent" : {
  		"search.max_open_scroll_context": 2012345678
  	},
  
  	"transient": {
  		"search.max_open_scroll_context": 2012345678
  	}
  }