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/handler_test.go b/middleware/dnssec/handler_test.go
index 37a92935a..60847d17b 100644
--- a/middleware/dnssec/handler_test.go
+++ b/middleware/dnssec/handler_test.go
@@ -6,10 +6,10 @@ import (
 	"testing"
 
 	"github.com/coredns/coredns/middleware/file"
+	"github.com/coredns/coredns/middleware/pkg/cache"
 	"github.com/coredns/coredns/middleware/pkg/dnsrecorder"
 	"github.com/coredns/coredns/middleware/test"
 
-	"github.com/hashicorp/golang-lru"
 	"github.com/miekg/dns"
 	"golang.org/x/net/context"
 )
@@ -89,8 +89,8 @@ func TestLookupZone(t *testing.T) {
 	dnskey, rm1, rm2 := newKey(t)
 	defer rm1()
 	defer rm2()
-	cache, _ := lru.New(defaultCap)
-	dh := New([]string{"miek.nl."}, []*DNSKEY{dnskey}, fm, cache)
+	c := cache.New(defaultCap)
+	dh := New([]string{"miek.nl."}, []*DNSKEY{dnskey}, fm, c)
 	ctx := context.TODO()
 
 	for _, tc := range dnsTestCases {
@@ -128,8 +128,8 @@ func TestLookupDNSKEY(t *testing.T) {
 	dnskey, rm1, rm2 := newKey(t)
 	defer rm1()
 	defer rm2()
-	cache, _ := lru.New(defaultCap)
-	dh := New([]string{"miek.nl."}, []*DNSKEY{dnskey}, test.ErrorHandler(), cache)
+	c := cache.New(defaultCap)
+	dh := New([]string{"miek.nl."}, []*DNSKEY{dnskey}, test.ErrorHandler(), c)
 	ctx := context.TODO()
 
 	for _, tc := range dnssecTestCases {