8555716046
For some reasons there was a dnsserver/middleware.go that defined the middleware handlers. This code was a repeat from middleware/middleware.go. Removed dnsserver/middleware.go and replaced all uses of dnsserver.Middleware with middleware.Middleware. Added dnsserver/address_test.go to test the zone normalization (and to improve the test coverage). The deleted file will also improve the test coverage :)
cache
cache enables a frontend cache.
Syntax
cache [ttl] [zones...]
ttlmax TTL in seconds. If not specified, the TTL of the reply (SOA minimum or minimum TTL in the answer section) will be used.zoneszones 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. For the negative cache, the SOA's MinTTL value is used.
A cache mostly makes sense with a middleware that is potentially slow (e.g., a proxy that retrieves an answer), or to minimize backend queries for middleware like etcd. Using a cache with the file middleware essentially doubles the memory load with no conceivable increase of query speed.
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).