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// Copyright 2014 The Macaron Authors
//
// Licensed under the Apache License, Version 2.0 (the "License"): you may
// not use this file except in compliance with the License. You may obtain
// a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
// License for the specific language governing permissions and limitations
// under the License.
package cache
import (
"crypto/md5"
"database/sql"
"encoding/hex"
"log"
"time"
_ "github.com/lib/pq"
"github.com/tango-contrib/cache"
)
// PostgresCacher represents a postgres cache adapter implementation.
type PostgresCacher struct {
c *sql.DB
interval int
}
// NewPostgresCacher creates and returns a new postgres cacher.
func NewPostgresCacher() *PostgresCacher {
return &PostgresCacher{}
}
func (c *PostgresCacher) md5(key string) string {
m := md5.Sum([]byte(key))
return hex.EncodeToString(m[:])
}
// Put puts value into cache with key and expire time.
// If expired is 0, it will be deleted by next GC operation.
func (c *PostgresCacher) Put(key string, val interface{}, expire int64) error {
item := &cache.Item{Val: val}
data, err := cache.EncodeGob(item)
if err != nil {
return err
}
now := time.Now().Unix()
if c.IsExist(key) {
_, err = c.c.Exec("UPDATE cache SET data=$1, created=$2, expire=$3 WHERE key=$4", data, now, expire, c.md5(key))
} else {
_, err = c.c.Exec("INSERT INTO cache(key,data,created,expire) VALUES($1,$2,$3,$4)", c.md5(key), data, now, expire)
}
return err
}
func (c *PostgresCacher) read(key string) (*cache.Item, error) {
var (
data []byte
created int64
expire int64
)
err := c.c.QueryRow("SELECT data,created,expire FROM cache WHERE key=$1", c.md5(key)).Scan(&data, &created, &expire)
if err != nil {
return nil, err
}
item := new(cache.Item)
if err = cache.DecodeGob(data, item); err != nil {
return nil, err
}
item.Created = created
item.Expire = expire
return item, nil
}
// Get gets cached value by given key.
func (c *PostgresCacher) Get(key string) interface{} {
item, err := c.read(key)
if err != nil {
return nil
}
if item.Expire > 0 &&
(time.Now().Unix()-item.Created) >= item.Expire {
c.Delete(key)
return nil
}
return item.Val
}
// Delete deletes cached value by given key.
func (c *PostgresCacher) Delete(key string) error {
_, err := c.c.Exec("DELETE FROM cache WHERE key=$1", c.md5(key))
return err
}
// Incr increases cached int-type value by given key as a counter.
func (c *PostgresCacher) Incr(key string) error {
item, err := c.read(key)
if err != nil {
return err
}
item.Val, err = cache.Incr(item.Val)
if err != nil {
return err
}
return c.Put(key, item.Val, item.Expire)
}
// Decrease cached int value.
func (c *PostgresCacher) Decr(key string) error {
item, err := c.read(key)
if err != nil {
return err
}
item.Val, err = cache.Decr(item.Val)
if err != nil {
return err
}
return c.Put(key, item.Val, item.Expire)
}
// IsExist returns true if cached value exists.
func (c *PostgresCacher) IsExist(key string) bool {
var data []byte
err := c.c.QueryRow("SELECT data FROM cache WHERE key=$1", c.md5(key)).Scan(&data)
if err != nil && err != sql.ErrNoRows {
panic("cache/postgres: error checking existence: " + err.Error())
}
return err != sql.ErrNoRows
}
// Flush deletes all cached data.
func (c *PostgresCacher) Flush() error {
_, err := c.c.Exec("DELETE FROM cache")
return err
}
func (c *PostgresCacher) startGC() {
if c.interval < 1 {
return
}
if _, err := c.c.Exec("DELETE FROM cache WHERE EXTRACT(EPOCH FROM NOW()) - created >= expire"); err != nil {
log.Printf("cache/postgres: error garbage collecting: %v", err)
}
time.AfterFunc(time.Duration(c.interval)*time.Second, func() { c.startGC() })
}
// StartAndGC starts GC routine based on config string settings.
func (c *PostgresCacher) StartAndGC(opt cache.Options) (err error) {
c.interval = opt.Interval
c.c, err = sql.Open("postgres", opt.AdapterConfig)
if err != nil {
return err
} else if err = c.c.Ping(); err != nil {
return err
}
go c.startGC()
return nil
}
func init() {
cache.Register("postgres", NewPostgresCacher())
}