140 lines
4.0 KiB
Markdown
140 lines
4.0 KiB
Markdown
# 6.3 Session storage
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We introduced a simple session manager's working principles in the previous section, and among other things, we defined a session storage interface. In this section, I'm going to show you an example of a memory based session storage engine that implements this interface. You can tailor this to other forms of session storage as well.
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package memory
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import (
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"container/list"
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"github.com/astaxie/session"
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"sync"
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"time"
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)
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var pder = &Provider{list: list.New()}
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type SessionStore struct {
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sid string // unique session id
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timeAccessed time.Time // last access time
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value map[interface{}]interface{} // session value stored inside
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}
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func (st *SessionStore) Set(key, value interface{}) error {
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st.value[key] = value
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pder.SessionUpdate(st.sid)
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return nil
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}
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func (st *SessionStore) Get(key interface{}) interface{} {
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pder.SessionUpdate(st.sid)
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if v, ok := st.value[key]; ok {
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return v
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} else {
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return nil
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}
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return nil
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}
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func (st *SessionStore) Delete(key interface{}) error {
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delete(st.value, key)
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pder.SessionUpdate(st.sid)
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return nil
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}
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func (st *SessionStore) SessionID() string {
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return st.sid
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}
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type Provider struct {
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lock sync.Mutex // lock
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sessions map[string]*list.Element // save in memory
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list *list.List // gc
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}
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func (pder *Provider) SessionInit(sid string) (session.Session, error) {
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pder.lock.Lock()
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defer pder.lock.Unlock()
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v := make(map[interface{}]interface{}, 0)
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newsess := &SessionStore{sid: sid, timeAccessed: time.Now(), value: v}
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element := pder.list.PushBack(newsess)
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pder.sessions[sid] = element
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return newsess, nil
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}
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func (pder *Provider) SessionRead(sid string) (session.Session, error) {
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if element, ok := pder.sessions[sid]; ok {
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return element.Value.(*SessionStore), nil
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} else {
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sess, err := pder.SessionInit(sid)
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return sess, err
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}
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return nil, nil
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}
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func (pder *Provider) SessionDestroy(sid string) error {
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if element, ok := pder.sessions[sid]; ok {
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delete(pder.sessions, sid)
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pder.list.Remove(element)
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return nil
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}
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return nil
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}
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func (pder *Provider) SessionGC(maxlifetime int64) {
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pder.lock.Lock()
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defer pder.lock.Unlock()
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for {
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element := pder.list.Back()
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if element == nil {
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break
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}
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if (element.Value.(*SessionStore).timeAccessed.Unix() + maxlifetime) < time.Now().Unix() {
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pder.list.Remove(element)
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delete(pder.sessions, element.Value.(*SessionStore).sid)
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} else {
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break
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}
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}
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}
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func (pder *Provider) SessionUpdate(sid string) error {
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pder.lock.Lock()
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defer pder.lock.Unlock()
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if element, ok := pder.sessions[sid]; ok {
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element.Value.(*SessionStore).timeAccessed = time.Now()
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pder.list.MoveToFront(element)
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return nil
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}
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return nil
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}
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func init() {
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pder.sessions = make(map[string]*list.Element, 0)
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session.Register("memory", pder)
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}
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The above example implements a memory based session storage mechanism. It uses its `init()` function to register this storage engine to the session manager. So how do we register this engine from our main program?
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import (
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"github.com/astaxie/session"
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_ "github.com/astaxie/session/providers/memory"
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)
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We use the blank import mechanism (which will invoke the package's `init()` function automatically) to register this engine to a session manager. We then use the following code to initialize the session manager:
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var globalSessions *session.Manager
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// initialize in init() function
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func init() {
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globalSessions, _ = session.NewManager("memory", "gosessionid", 3600)
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go globalSessions.GC()
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}
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## Links
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- [Directory](preface.md)
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- Previous section: [How to use sessions in Go](06.2.md)
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- Next section: [Prevent session hijacking](06.4.md)
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