middleware/cache: split cache in positive and negative and use lru (#298)

Make the cache memory bounded, by using a LRU cache. Also split the
cache in a positive and negative one - each with its own controls.

Extend the cache stanza to allow for this:

    cache {
       positive limit [ttl]
       negative limit [ttl]
    }

is now possible. This also add a cache_test.go in the toplevel test/
directory that exercises the caching path.

Fixes #260

1 files changed, 89 insertions, 0 deletions

diff --git a/test/cache_test.go b/test/cache_test.go
new file mode 100644
index 000000000..8382aabba
--- /dev/null
+++ b/test/cache_test.go
@@ -0,0 +1,89 @@
+package test
+
+import (
+	"io/ioutil"
+	"log"
+	"testing"
+	"time"
+
+	"github.com/miekg/coredns/middleware/proxy"
+	"github.com/miekg/coredns/middleware/test"
+	"github.com/miekg/coredns/request"
+
+	"github.com/miekg/dns"
+)
+
+// This tests uses the exampleOrg zone as defined in proxy_test.go
+
+func TestLookupCache(t *testing.T) {
+	// Start auth. CoreDNS holding the auth zone.
+	name, rm, err := test.TempFile(t, ".", exampleOrg)
+	if err != nil {
+		t.Fatalf("failed to created zone: %s", err)
+	}
+	defer rm()
+
+	corefile := `example.org:0 {
+       file ` + name + `
+}
+`
+	i, err := CoreDNSServer(corefile)
+	if err != nil {
+		t.Fatalf("Could not get CoreDNS serving instance: %s", err)
+	}
+
+	udp, _ := CoreDNSServerPorts(i, 0)
+	if udp == "" {
+		t.Fatalf("Could not get UDP listening port")
+	}
+	defer i.Stop()
+
+	// Start caching proxy CoreDNS that we want to test.
+	corefile = `example.org:0 {
+	proxy . ` + udp + `
+	cache
+}
+`
+	i, err = CoreDNSServer(corefile)
+	if err != nil {
+		t.Fatalf("Could not get CoreDNS serving instance: %s", err)
+	}
+
+	udp, _ = CoreDNSServerPorts(i, 0)
+	if udp == "" {
+		t.Fatalf("Could not get UDP listening port")
+	}
+	defer i.Stop()
+
+	log.SetOutput(ioutil.Discard)
+
+	p := proxy.New([]string{udp})
+	state := request.Request{W: &test.ResponseWriter{}, Req: new(dns.Msg)}
+
+	resp, err := p.Lookup(state, "example.org.", dns.TypeA)
+	if err != nil {
+		t.Fatal("Expected to receive reply, but didn't")
+	}
+	// expect answer section with A record in it
+	if len(resp.Answer) == 0 {
+		t.Error("Expected to at least one RR in the answer section, got none")
+	}
+
+	ttl := resp.Answer[0].Header().Ttl
+
+	time.Sleep(2 * time.Second) // TODO(miek): meh.
+
+	resp, err = p.Lookup(state, "example.org.", dns.TypeA)
+	if err != nil {
+		t.Fatal("Expected to receive reply, but didn't")
+	}
+
+	// expect answer section with A record in it
+	if len(resp.Answer) == 0 {
+		t.Error("Expected to at least one RR in the answer section, got none")
+	}
+	newTTL := resp.Answer[0].Header().Ttl
+	if newTTL >= ttl {
+		t.Errorf("Expected TTL to be lower than: %d, got %d", ttl, newTTL)
+	}
+}