6bbefe3f18
Cache negative results, too, but only with half TTL, as configured. Plus get rid of "mesg.Id = req.Id" data race (build with -race flag) at once without locking. Found another data race: delete must be protected with Lock, RLock is not enough.
165 lines
2.5 KiB
Go
165 lines
2.5 KiB
Go
package main
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import (
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"crypto/md5"
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"encoding/json"
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"fmt"
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"sync"
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"time"
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"github.com/hoisie/redis"
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"github.com/miekg/dns"
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)
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type KeyNotFound struct {
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key string
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}
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func (e KeyNotFound) Error() string {
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return e.key + " " + "not found"
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}
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type KeyExpired struct {
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Key string
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}
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func (e KeyExpired) Error() string {
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return e.Key + " " + "expired"
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}
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type CacheIsFull struct {
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}
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func (e CacheIsFull) Error() string {
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return "Cache is Full"
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}
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type SerializerError struct {
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}
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func (e SerializerError) Error() string {
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return "Serializer error"
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}
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type Mesg struct {
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Msg *dns.Msg
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Expire time.Time
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}
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type Cache interface {
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Get(key string) (Msg *dns.Msg, err error)
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Set(key string, Msg *dns.Msg) error
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Exists(key string) bool
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Remove(key string)
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Length() int
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}
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type MemoryCache struct {
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Backend map[string]Mesg
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Expire time.Duration
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Maxcount int
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mu sync.RWMutex
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}
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func (c *MemoryCache) Get(key string) (*dns.Msg, error) {
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c.mu.RLock()
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mesg, ok := c.Backend[key]
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c.mu.RUnlock()
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if !ok {
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return nil, KeyNotFound{key}
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}
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if mesg.Expire.Before(time.Now()) {
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c.Remove(key)
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return nil, KeyExpired{key}
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}
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return mesg.Msg, nil
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}
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func (c *MemoryCache) Set(key string, msg *dns.Msg) error {
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if c.Full() && !c.Exists(key) {
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return CacheIsFull{}
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}
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expire := time.Now().Add(c.Expire)
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mesg := Mesg{msg, expire}
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c.mu.Lock()
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c.Backend[key] = mesg
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c.mu.Unlock()
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return nil
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}
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func (c *MemoryCache) Remove(key string) {
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c.mu.Lock()
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delete(c.Backend, key)
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c.mu.Unlock()
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}
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func (c *MemoryCache) Exists(key string) bool {
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c.mu.RLock()
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_, ok := c.Backend[key]
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c.mu.RUnlock()
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return ok
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}
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func (c *MemoryCache) Length() int {
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c.mu.RLock()
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defer c.mu.RUnlock()
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return len(c.Backend)
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}
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func (c *MemoryCache) Full() bool {
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// if Maxcount is zero. the cache will never be full.
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if c.Maxcount == 0 {
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return false
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}
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return c.Length() >= c.Maxcount
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}
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/*
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TODO: Redis cache Backend
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*/
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type RedisCache struct {
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Backend *redis.Client
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Serializer JsonSerializer
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Expire time.Duration
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Maxcount int
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}
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func (c *RedisCache) Get() {
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}
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func (c *RedisCache) Set() {
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}
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func (c *RedisCache) Remove() {
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}
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func KeyGen(q Question) string {
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h := md5.New()
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h.Write([]byte(q.String()))
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x := h.Sum(nil)
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key := fmt.Sprintf("%x", x)
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return key
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}
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type JsonSerializer struct {
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}
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func (*JsonSerializer) Dumps(mesg *dns.Msg) (encoded []byte, err error) {
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encoded, err = json.Marshal(mesg)
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return
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}
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func (*JsonSerializer) Loads(data []byte, mesg **dns.Msg) error {
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err := json.Unmarshal(data, mesg)
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return err
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}
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