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Miek Gieben e54c232c8c middleware/cache: split cache in positive and negative and use lru (#298 )

Make the cache memory bounded, by using a LRU cache. Also split the
cache in a positive and negative one - each with its own controls.

Extend the cache stanza to allow for this:

    cache {
       positive limit [ttl]
       negative limit [ttl]
    }

is now possible. This also add a cache_test.go in the toplevel test/
directory that exercises the caching path.

Fixes #260

2016-10-02 08:31:44 +01:00

cache_test.go

middleware/cache: split cache in positive and negative and use lru (#298 )

2016-10-02 08:31:44 +01:00

cache.go

middleware/cache: split cache in positive and negative and use lru (#298 )

2016-10-02 08:31:44 +01:00

handler.go

middleware/cache: split cache in positive and negative and use lru (#298 )

2016-10-02 08:31:44 +01:00

item_test.go

middleware/cache: split cache in positive and negative and use lru (#298 )

2016-10-02 08:31:44 +01:00

item.go

middleware/cache: split cache in positive and negative and use lru (#298 )

2016-10-02 08:31:44 +01:00

README.md

middleware/cache: split cache in positive and negative and use lru (#298 )

2016-10-02 08:31:44 +01:00

setup_test.go

middleware/cache: split cache in positive and negative and use lru (#298 )

2016-10-02 08:31:44 +01:00

setup.go

middleware/cache: split cache in positive and negative and use lru (#298 )

2016-10-02 08:31:44 +01:00

README.md

cache

cache enables a frontend cache.

Syntax

cache [ttl] [zones...]

ttl max TTL in seconds. If not specified, the maximum TTL will be used which is 1 hours for positive responses and half an hour for negative ones.
zones zones it should cache for. If empty, the zones from the configuration block are used.

Each element in the cache is cached according to its TTL (with ttl as the max). For the negative cache, the SOA's MinTTL value is used. A cache can contain up to 10,000 items by default.

Or if you want more control:

cache [ttl] [zones...] {
    postive capacity [ttl]
    negative capacity [ttl]
}

ttl and zones as above.
positive, override the settings for caching positive responses, capacity indicates the maximum number of packets we cache before we start evicting (LRU). Ttl overrides the cache maximum TTL.
negative, override the settings for caching negative responses, capacity indicates the maximum number of packets we cache before we start evicting (LRU). Ttl overrides the cache maximum TTL.

The minimum TTL allowed on resource records is 5 seconds.

If monitoring is enabled (via the prometheus directive) then the following extra metrics are added:

coredns_cache_hit_count_total, and
coredns_cache_miss_count_total

They both work on a per-zone basis and just count the hit and miss counts for each query.

Examples

cache 10

Enable caching for all zones, but cap everything to a TTL of 10 seconds.

proxy . 8.8.8.8:53
cache example.org

Proxy to Google Public DNS and only cache responses for example.org (or below).