Merge pull request #25 from dbalan/memcached_backend_support

Memcached backend support

cache.go

@@ -7,6 +7,7 @@ import (
 	"sync"
 	"time"
 
+	"github.com/bradfitz/gomemcache/memcache"
 	"github.com/hoisie/redis"
 	"github.com/miekg/dns"
 )
@@ -35,10 +36,11 @@ func (e CacheIsFull) Error() string {
 }
 
 type SerializerError struct {
+	err error
 }
 
 func (e SerializerError) Error() string {
-	return "Serializer error"
+	return fmt.Sprintf("Serializer error: got %v", e.err)
 }
 
 type Mesg struct {
@@ -50,8 +52,8 @@ type Cache interface {
 	Get(key string) (Msg *dns.Msg, err error)
 	Set(key string, Msg *dns.Msg) error
 	Exists(key string) bool
-	Remove(key string)
-	Length() int
+	Remove(key string) error
+	Full() bool
 }
 
 type MemoryCache struct {
@@ -91,10 +93,11 @@ func (c *MemoryCache) Set(key string, msg *dns.Msg) error {
 	return nil
 }
 
-func (c *MemoryCache) Remove(key string) {
+func (c *MemoryCache) Remove(key string) error {
 	c.mu.Lock()
 	delete(c.Backend, key)
 	c.mu.Unlock()
+	return nil
 }
 
 func (c *MemoryCache) Exists(key string) bool {
@@ -118,6 +121,70 @@ func (c *MemoryCache) Full() bool {
 	return c.Length() >= c.Maxcount
 }
 
+/*
+Memcached backend
+*/
+
+func NewMemcachedCache(servers []string, expire int32) *MemcachedCache {
+	c := memcache.New(servers...)
+	return &MemcachedCache{
+		backend: c,
+		expire:  expire,
+	}
+}
+
+type MemcachedCache struct {
+	backend *memcache.Client
+	expire  int32
+}
+
+func (m *MemcachedCache) Set(key string, msg *dns.Msg) error {
+	var val []byte
+	var err error
+
+	// handle cases for negacache where it sets nil values
+	if msg == nil {
+		val = []byte("nil")
+	} else {
+		val, err = msg.Pack()
+	}
+	if err != nil {
+		err = SerializerError{err}
+	}
+	return m.backend.Set(&memcache.Item{Key: key, Value: val, Expiration: m.expire})
+}
+
+func (m *MemcachedCache) Get(key string) (*dns.Msg, error) {
+	var msg dns.Msg
+	item, err := m.backend.Get(key)
+	if err != nil {
+		err = KeyNotFound{key}
+		return &msg, err
+	}
+	err = msg.Unpack(item.Value)
+	if err != nil {
+		err = SerializerError{err}
+	}
+	return &msg, err
+}
+
+func (m *MemcachedCache) Exists(key string) bool {
+	_, err := m.backend.Get(key)
+	if err != nil {
+		return true
+	}
+	return false
+}
+
+func (m *MemcachedCache) Remove(key string) error {
+	return m.backend.Delete(key)
+}
+
+func (m *MemcachedCache) Full() bool {
+	// memcache is never full (LRU)
+	return false
+}
+
 /*
 TODO: Redis cache Backend
 */
@@ -149,16 +216,18 @@ func KeyGen(q Question) string {
 	return key
 }
 
+/* we need to define marsheling to encode and decode
+ */
 type JsonSerializer struct {
 }
 
 func (*JsonSerializer) Dumps(mesg *dns.Msg) (encoded []byte, err error) {
-	encoded, err = json.Marshal(mesg)
+	encoded, err = json.Marshal(*mesg)
 	return
 }
 
-func (*JsonSerializer) Loads(data []byte, mesg **dns.Msg) error {
-	err := json.Unmarshal(data, mesg)
-	return err
-
+func (*JsonSerializer) Loads(data []byte) (*dns.Msg, error) {
+	var mesg dns.Msg
+	err := json.Unmarshal(data, &mesg)
+	return &mesg, err
 }

godns.conf

@@ -24,6 +24,9 @@ port = 6379
 db = 0
 password =""
 
+[memcache]
+servers = ["127.0.0.1:11211"]
+
 [log]
 stdout = true
 file = "./godns.log"
@@ -32,7 +35,7 @@ level = "INFO"  #DEBUG | INFO |NOTICE | WARN | ERROR
 
 
 [cache]
-# backend option [memory|redis]	
+# backend option [memory|memcache|redis]	
 # redis backend not implemented yet
 backend = "memory"  
 expire = 600  # 10 minutes

handler.go

@@ -61,6 +61,13 @@ func NewHandler() *GODNSHandler {
 			Expire:   time.Duration(cacheConfig.Expire) * time.Second / 2,
 			Maxcount: cacheConfig.Maxcount,
 		}
+	case "memcache":
+		cache = NewMemcachedCache(
+			settings.Memcache.Servers,
+			int32(cacheConfig.Expire))
+		negCache = NewMemcachedCache(
+			settings.Memcache.Servers,
+			int32(cacheConfig.Expire/2))
 	case "redis":
 		// cache = &MemoryCache{
 		// 	Backend:    make(map[string]*dns.Msg),

settings.go

@@ -27,6 +27,7 @@ type Settings struct {
 	Server       DNSServerSettings `toml:"server"`
 	ResolvConfig ResolvSettings    `toml:"resolv"`
 	Redis        RedisSettings     `toml:"redis"`
+	Memcache     MemcacheSettings  `toml:"memcache"`
 	Log          LogSettings       `toml:"log"`
 	Cache        CacheSettings     `toml:"cache"`
 	Hosts        HostsSettings     `toml:"hosts"`
@@ -50,6 +51,10 @@ type RedisSettings struct {
 	Password string
 }
 
+type MemcacheSettings struct {
+	Servers []string
+}
+
 func (s RedisSettings) Addr() string {
 	return s.Host + ":" + strconv.Itoa(s.Port)
 }