godns/cache/cache_redis.go

package cache

import (
	"github.com/go-redis/redis/v7"
	"github.com/miekg/dns"
	"meow.tf/joker/godns/settings"
	"time"
)

func NewRedisCache(c settings.RedisSettings, expire time.Duration) *RedisCache {
	rc := redis.NewClient(&redis.Options{Addr: c.Addr(), DB: c.DB, Password: c.Password})

	return &RedisCache{
		backend: rc,
		expire:  expire,
	}
}

type RedisCache struct {
	Cache

	backend    *redis.Client
	expire     time.Duration
}

func (m *RedisCache) Set(key string, msg *dns.Msg) error {
	var val []byte
	var err error

	key = "cache:" + key

	// 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(key, val, m.expire).Err()
}

func (m *RedisCache) Get(key string) (*dns.Msg, error) {
	var msg dns.Msg
	var err error
	key = "cache:" + key

	item, err := m.backend.Get(key).Bytes()

	if err != nil {
		err = KeyNotFound{key}
		return &msg, err
	}

	err = msg.Unpack(item)
	if err != nil {
		err = SerializerError{err}
	}
	return &msg, err
}

func (m *RedisCache) Exists(key string) bool {
	res, err := m.backend.Exists(key).Result()

	if err != nil {
		return true
	}

	return res == 1
}

func (m *RedisCache) Remove(key string) error {
	return m.backend.Del(key).Err()
}

func (m *RedisCache) Full() bool {
	// redis is never full (LRU)
	return false
}

func (m *RedisCache) Purge() error {
	iter := m.backend.Scan(0, "cache:*", 0).Iterator()

	if iter.Err() != nil {
		return iter.Err()
	}

	var err error

	for iter.Next() {
		err = m.backend.Del(iter.Val()).Err()

		if err != nil {
			return err
		}
	}

	return nil
}