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44 lines
1.2 KiB
Markdown
44 lines
1.2 KiB
Markdown
# cache
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`cache` enables a frontend cache.
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## Syntax
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~~~
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cache [ttl] [zones...]
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~~~
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* `ttl` max TTL in seconds. If not specified, the TTL of the reply (SOA minimum or minimum TTL in the
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answer section) will be used.
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* `zones` zones it should cache for. If empty, the zones from the configuration block are used.
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Each element in the cache is cached according to its TTL. For the negative cache, the SOA's MinTTL
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value is used.
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A cache mostly makes sense with a middleware that is potentially slow (e.g., a proxy that retrieves an
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answer), or to minimize backend queries for middleware like etcd. Using a cache with the file
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middleware essentially doubles the memory load with no conceivable increase of query speed.
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The minimum TTL allowed on resource records is 5 seconds.
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If monitoring is enabled (via the `prometheus` directive) then the following extra metrics are added:
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* coredns_cache_hit_count_total, and
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* coredns_cache_miss_count_total
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They both work on a per-zone basis and just count the hit and miss counts for each query.
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## Examples
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~~~
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cache 10
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~~~
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Enable caching for all zones, but cap everything to a TTL of 10 seconds.
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~~~
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proxy . 8.8.8.8:53
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cache example.org
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~~~
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Proxy to Google Public DNS and only cache responses for example.org (or below).
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