How Do I Clear the Cache of a CSS Cluster?

During aggregation and sorting, data are converted to the fielddata structure, which occupies a large amount of memory.

1. Run the following commands on Kibana to check the memory occupied by index fielddata:

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

2. If the memory usage of fielddata is too high, you can run the following command to clear fielddata:

   POST /test/_cache/clear?fielddata=true 

In the preceding command, test indicates the name of the index whose fielddata occupies a large amount of memory.

The FST structure of each segment is loaded to the memory and will not be cleared. If the number of index segments is too large, the memory usage will be high. You are advised to periodically clear the segments.

1. Run the following command on Kibana to check the number of segments and their memory usage on each node:

   GET /_cat/nodes?v&h=segments.count,segments.memory&s=segments.memory:desc

2. If the memory usage of segments is too high, you can delete or disable unnecessary indexes, or periodically combine indexes that are not updated.

Run the following command on Kibana to clear the cache:

POST _cache/clear