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Published: Jul 11, 2016 License: Apache-2.0 Imports: 9 Imported by: 0



cache enables a frontend cache.


cache [ttl] [zones...]
  • ttl max TTL in seconds, if not specified the TTL of the reply (SOA minimum or minimum TTL in the answer section) will be used.
  • zones zones it should should cache for. If empty the zones from the configuration block are used.

Each element in the cache is cached according to its TTL, for the negative cache the SOA's MinTTL value is used.

A cache mostly makes sense with a middleware that is potentially slow, i.e. a proxy that retrieves answer, or to minimize backend queries for middleware like etcd. Using a cache with the file middleware essentially doubles the memory load with no concealable increase of query speed.

The minimum TTL allowed on resource records is 5 seconds.

If monitoring is enabled (prometheus directive) then the following 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.


cache 10

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

proxy .

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




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type Cache

type Cache struct {
	Next  middleware.Handler
	Zones []string
	// contains filtered or unexported fields

Cache is middleware that looks up responses in a cache and caches replies.

func NewCache

func NewCache(ttl int, zones []string, next middleware.Handler) Cache

func (Cache) ServeDNS

func (c Cache) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error)

ServeDNS implements the middleware.Handler interface.

type CachingResponseWriter

type CachingResponseWriter struct {
	// contains filtered or unexported fields

func NewCachingResponseWriter

func NewCachingResponseWriter(w dns.ResponseWriter, cache *gcache.Cache, cap time.Duration) *CachingResponseWriter

func (*CachingResponseWriter) Hijack

func (c *CachingResponseWriter) Hijack()

func (*CachingResponseWriter) Write

func (c *CachingResponseWriter) Write(buf []byte) (int, error)

func (*CachingResponseWriter) WriteMsg

func (c *CachingResponseWriter) WriteMsg(res *dns.Msg) error

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