cache #

Description #

The cache filter is composed of the get_cache and set_cache filters, which need to be used in combination. The cache filter is used to cache accelerated queries, prevent repeated requests, and reduce the query pressure of back-end clusters.

get_cache Filter #

The get_cache filter is used to acquire previous messages from the cache and return them to the client, without needing to access the back-end Elasticsearch. It is intended to cache hotspot data.

A configuration example is as follows:

flow:
  - name: get_cache
    filter:
      - get_cache:
          pass_patterns: ["_cat","scroll", "scroll_id","_refresh","_cluster","_ccr","_count","_flush","_ilm","_ingest","_license","_migration","_ml","_rollup","_data_stream","_open", "_close"]

Parameter Description #

Name	Type	Description
pass_patterns	string	Rule for ignoring the cache for a request. The cache is skipped when the URL contains any defined keyword.

set_cache Filter #

The set_cache filter is used to cache results returned through back-end query. Expiration time can be set for the cache.

A configuration example is as follows:

flow:
  - name: get_cache
    filter:
      - set_cache:
          min_response_size: 100
          max_response_size: 1024000
          cache_ttl: 30s
          max_cache_items: 100000

Parameter Description #

Name	Type	Description
cache_type	string	Cache type. It can be set to `ristretto`, `ccache`, or `redis`, and the default value is `ristretto`.
cache_ttl	string	Expiration time of the cache. The default value is `10s`.
async_search_cache_ttl	string	Expiration time of the cache for storing asynchronous request results. The default value is `10m`.
min_response_size	int	Minimum message body size that meets cache requirements. The default value is `-1`, indicating an unlimited value.
max_response_size	int	Maximum message body size that meets cache requirements. The default value is the maximum value of the int parameter.
max_cached_item	int	Maximum number of messages that can be cached. The default value is `1000000`. The value is valid when the cache type is `ccache`.
max_cached_size	int	Maximum cache memory overhead. The default value is `1000000000`, that is, 1 GB. The value is valid when the cache type is `ristretto`.
validated_status_code	array	Request status code that is allowed to be cached. The default value is `200,201,404,403,413,400,301`.

Other Parameters #

If you want to ignore caching, you can define no_cache in the URL parameters to cause the gateway to ignore caching. For example:

curl http://localhost:8000/_search?no_cache=true