Enhanced Cold Data Query Performance¶

Context¶

When you query data on the Discover page of Kibana for the first time, all data needs to be obtained from OBS because there is no cache. If a large number of documents are returned, it takes a long time to obtain the corresponding time fields and file metadata from OBS. To accelerate queries the first time they run on the Discover page, you can cache data locally.

Prerequisites¶

This feature is available in Elasticsearch clusters of versions 7.6.2 and 7.10.2 and OpenSearch clusters created after February 2023.

API for Querying Cold Data from Local Cache¶

This API can be used to query the cold data from local cache.

Example request:

GET /_frozen_stats/local_cache
GET /_frozen_stats/local_cache/{nodeId}

Response example:

{
   "_nodes" : {
     "total" : 1,
     "successful" : 1,
     "failed" : 0
   },
   "cluster_name" : "elasticsearch",
   "nodes" : {
     "6by3lPy1R3m55Dcq3liK8Q" : {
       "name" : "node-1",
       "transport_address" : "127.0.0.1:9300",
       "host" : "127.0.0.1",
       "ip" : "127.0.0.1",
       "local_cache" : {
         "get_stats" : {
           "get_total_count" : 562,                            //Total number of times data was retrieved from the local cold data cache.
           "get_hit_count" : 562,                              //Total number of hits in the local cold data cache.
           "get_miss_count" : 0,                               //Total number of local cold data cache misses.
           "get_total_ns" : 43849200,                          //Total duration for retrieving data from the local cold data cache.
           "get_avg_ns" : 78023                                //Average duration for retrieving data from the local cold data cache.
         },
         "load_stats" : {
           "load_count" : 2,                                    //Number of times cold data was loaded from the local cache
           "load_total_ms" : 29,                                //Total duration for loading cold data from the local cache
           "load_avg_ms" : 14,                                  //Average duration for loading cold data from the local cache
           "load_fail_count" : 0,                               //Number of failure times for loading cold data from the local cache
           "load_overflow_count" : 0                            //Number of times the local cold data cache exceeds the cache pool size.
         },
         "reload_stats" : {
           "reload_count" : 0,                                  //Number of times the local cold data cache was regenerated.
           "reload_total_ms" : 0,                               //Total duration for regenerating the local cold data cache.
           "reload_avg_ms" : 0,                                 //Average duration for regenerating the local cold data cache.
           "reload_fail_count" : 0                              //Number of failures in regenerating the local cold data cache.
         },
         "init_stats" : {
           "init_count" : 0,                                     //Number of times the local cold data cache was initialized.
           "init_total_ms" : 0,                                  //Total duration for initializing the local cold data cache.
           "init_avg_ms" : 0,                                    //Average duration for initializing the local cold data cache.
           "init_fail_count" : 0                                 //Number of failures in initializing the local cold data cache.
         }
       }
     }
   }
 }

Configuring Parameters¶

Configuration Item	Type	Unit	Value Range	Scope	Can Be Dynamically Modified	Description
low_cost.local_cache.max.capacity	Integer	`-`	The value ranges from 10 to 5000. The default value is 500.	node	Yes	Maximum number of available cold data caches on a node. Each shard corresponds to a cache object. Note If the heap memory usage remains high, decrease the value. If the value of load_overflow_count keeps increasing rapidly, increase the value.
index.low_cost.local_cache.threshold	Integer	%	The value ranges from 0 to 100. The default value is 50.	index	Yes	Threshold for enabling the local cache of cold data. Note If the percentage of date fields is less than the value of this parameter, the cold data of the date type will be cached locally. Otherwise, this parameter is not used. If the date fields of the current index occupy most of the data volume of the current index, you are not advised using this function.
index.low_cost.local_cache.evict_time	String	Days	The value ranges from 1d to 365d. The default value is 30d.	index	Yes	Wait time before cold data is deleted from local cache. The value is determined based on index.frozen_date (time when the freezing is successful). Note For indexes that have been frozen in old clusters and do not have index.frozen_date specified, the value of this parameter is determined based on the index creation time. You are advised to adjust the deletion time based on the disk usage to avoid high disk usage.

Modifying Parameters¶

Run the following command to modify low_cost.local_cache.max.capacity:

PUT _cluster/settings
 {
   "persistent": {
     "low_cost.local_cache.max.capacity":1000
   }
 }

Run the following command to modify index.low_cost.local_cache.threshold:

PUT es_write_pref2-00000000021/_settings
 {
 "index.low_cost.local_cache.threshold":20
 }

Run the following command to modify index.low_cost.local_cache.evict_time:

PUT es_write_pref2-00000000021/_settings
 {
 "index.low_cost.local_cache.evict_time":"7d"
 }

last updated: 2024-12-10 15:01 UTC - commit: 0dd899b11a65d710b08ebf8c9328eecf32bcba6c