mirror of
https://github.com/golang/go
synced 2024-11-23 05:10:09 -07:00
83 lines
2.0 KiB
Go
83 lines
2.0 KiB
Go
// Copyright 2011 The Go Authors. All rights reserved.
|
|
// Use of this source code is governed by a BSD-style
|
|
// license that can be found in the LICENSE file.
|
|
|
|
package cache
|
|
|
|
import (
|
|
"fmt"
|
|
"net/http"
|
|
"time"
|
|
|
|
"appengine"
|
|
"appengine/memcache"
|
|
)
|
|
|
|
const (
|
|
nocache = "nocache"
|
|
timeKey = "cachetime"
|
|
expiry = 600 // 10 minutes
|
|
)
|
|
|
|
func newTime() uint64 { return uint64(time.Now().Unix()) << 32 }
|
|
|
|
// Now returns the current logical datastore time to use for cache lookups.
|
|
func Now(c appengine.Context) uint64 {
|
|
t, err := memcache.Increment(c, timeKey, 0, newTime())
|
|
if err != nil {
|
|
c.Errorf("cache.Now: %v", err)
|
|
return 0
|
|
}
|
|
return t
|
|
}
|
|
|
|
// Tick sets the current logical datastore time to a never-before-used time
|
|
// and returns that time. It should be called to invalidate the cache.
|
|
func Tick(c appengine.Context) uint64 {
|
|
t, err := memcache.Increment(c, timeKey, 1, newTime())
|
|
if err != nil {
|
|
c.Errorf("cache.Tick: %v", err)
|
|
return 0
|
|
}
|
|
return t
|
|
}
|
|
|
|
// Get fetches data for name at time now from memcache and unmarshals it into
|
|
// value. It reports whether it found the cache record and logs any errors to
|
|
// the admin console.
|
|
func Get(r *http.Request, now uint64, name string, value interface{}) bool {
|
|
if now == 0 || r.FormValue(nocache) != "" {
|
|
return false
|
|
}
|
|
c := appengine.NewContext(r)
|
|
key := fmt.Sprintf("%s.%d", name, now)
|
|
_, err := memcache.JSON.Get(c, key, value)
|
|
if err == nil {
|
|
c.Debugf("cache hit %q", key)
|
|
return true
|
|
}
|
|
c.Debugf("cache miss %q", key)
|
|
if err != memcache.ErrCacheMiss {
|
|
c.Errorf("get cache %q: %v", key, err)
|
|
}
|
|
return false
|
|
}
|
|
|
|
// Set puts value into memcache under name at time now.
|
|
// It logs any errors to the admin console.
|
|
func Set(r *http.Request, now uint64, name string, value interface{}) {
|
|
if now == 0 || r.FormValue(nocache) != "" {
|
|
return
|
|
}
|
|
c := appengine.NewContext(r)
|
|
key := fmt.Sprintf("%s.%d", name, now)
|
|
err := memcache.JSON.Set(c, &memcache.Item{
|
|
Key: key,
|
|
Object: value,
|
|
Expiration: expiry,
|
|
})
|
|
if err != nil {
|
|
c.Errorf("set cache %q: %v", key, err)
|
|
}
|
|
}
|