New cache implementation and prefetch handing in mw/cache (#731)

* cache: add sharded cache implementation

Add Cache impl and a few tests. This cache is 256-way sharded, mainly
so each shard has it's own lock. The main cache structure is a readonly
jump plane into the right shard.

This should remove the single lock contention on the main lock and
provide more concurrent throughput - Obviously this hasn't been tested
or measured.

The key into the cache was made a uint32 (hash.fnv) and the hashing op
is not using strings.ToLower anymore remove any GC in that code path.

* here too

* Minimum shard size

* typos

* blurp

* small cleanups no defer

* typo

* Add freq based on Johns idea

* cherry-pick conflict resolv

* typo

* update from early code review from john

* add prefetch to the cache

* mw/cache: add prefetch

* remove println

* remove comment

* Fix tests

* Test prefetch in setup

* Add start of cache

* try add diff cache options

* Add hacky testcase

* not needed

* allow the use of a percentage for prefetch

If the TTL falls below xx% do a prefetch, if the record was popular.
Some other fixes and correctly prefetch only popular records.

1 files changed, 5 insertions, 5 deletions

diff --git a/middleware/dnssec/dnssec_test.go b/middleware/dnssec/dnssec_test.go
index 1c9c9a545..3549a7c8f 100644
--- a/middleware/dnssec/dnssec_test.go
+++ b/middleware/dnssec/dnssec_test.go
@@ -4,10 +4,10 @@ import (
 	"testing"
 	"time"
 
+	"github.com/coredns/coredns/middleware/pkg/cache"
 	"github.com/coredns/coredns/middleware/test"
 	"github.com/coredns/coredns/request"
 
-	"github.com/hashicorp/golang-lru"
 	"github.com/miekg/dns"
 )
 
@@ -69,8 +69,8 @@ func TestSigningDifferentZone(t *testing.T) {
 
 	m := testMsgEx()
 	state := request.Request{Req: m}
-	cache, _ := lru.New(defaultCap)
-	d := New([]string{"example.org."}, []*DNSKEY{key}, nil, cache)
+	c := cache.New(defaultCap)
+	d := New([]string{"example.org."}, []*DNSKEY{key}, nil, c)
 	m = d.Sign(state, "example.org.", time.Now().UTC())
 	if !section(m.Answer, 1) {
 		t.Errorf("answer section should have 1 sig")
@@ -183,8 +183,8 @@ func testMsgDname() *dns.Msg {
 
 func newDnssec(t *testing.T, zones []string) (Dnssec, func(), func()) {
 	k, rm1, rm2 := newKey(t)
-	cache, _ := lru.New(defaultCap)
-	d := New(zones, []*DNSKEY{k}, nil, cache)
+	c := cache.New(defaultCap)
+	d := New(zones, []*DNSKEY{k}, nil, c)
 	return d, rm1, rm2
 }