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provider.go
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provider.go
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package sessions
import (
"sync"
"time"
)
type (
// provider contains the sessions and external databases (load and update).
// It's the session memory manager
provider struct {
// we don't use RWMutex because all actions have read and write at the same action function.
// (or write to a *Session's value which is race if we don't lock)
// narrow locks are fasters but are useless here.
mu sync.Mutex
sessions map[string]*Session
databases []Database
}
)
// newProvider returns a new sessions provider
func newProvider() *provider {
return &provider{
sessions: make(map[string]*Session, 0),
databases: make([]Database, 0),
}
}
// RegisterDatabase adds a session database
// a session db doesn't have write access
func (p *provider) RegisterDatabase(db Database) {
p.mu.Lock() // for any case
p.databases = append(p.databases, db)
p.mu.Unlock()
}
// newSession returns a new session from sessionid
func (p *provider) newSession(sid string, expires time.Duration) *Session {
onExpire := func() {
p.Destroy(sid)
}
values, lifetime := p.loadSessionFromDB(sid)
// simple and straight:
if !lifetime.IsZero() {
// if stored time is not zero
// start a timer based on the stored time, if not expired.
lifetime.Revive(onExpire)
} else {
// Remember: if db not exist or it has been expired
// then the stored time will be zero(see loadSessionFromDB) and the values will be empty.
//
// Even if the database has an unlimited session (possible by a previous app run)
// priority to the "expires" is given,
// again if <=0 then it does nothing.
lifetime.Begin(expires, onExpire)
}
// I ended up without the need of a duration field on lifetime,
// but these are some of my previous comments, they will be required for any future change.
//
// OK I think go has a bug when gob on embedded time.Time
// even if we `gob.Register(LifeTime)`
// the OriginalDuration is not saved to the gob file and it cannot be retrieved, it's always 0.
// But if we do not embed the `time.Time` inside the `LifeTime` then
// it's working.
// i.e type LifeTime struct { time.Time; OriginalDuration time.Duration} -> this doesn't
// type LifeTime struct {Time time.Time; OriginalDuration time.Duration} -> this works
// So we have two options:
// 1. don't embed the time.Time -> we will have to use lifetime.Time to get its functions, which doesn't seems right to me
// 2. embed the time.Time and compare their times with `lifetime.After(time.Now().Add(expires))`, it seems right but it
// should be slower.
//
// I'll use the 1. and put some common time.Time functions, like After, IsZero on the `LifeTime` type too.
//
// if db exists but its lifetime is bigger than the expires (very raire,
// the source code should be compatible with the databases,
// should we print a warning to the user? it is his/her fault
// use the database's lifetime or the configurated?
// if values.Len() > 0 && lifetime.OriginalDuration != expires {
// golog.Warnf(`session database: stored expire time(dur=%d) is differnet than the configuration(dur=%d)
// application will use the configurated one`, lifetime.OriginalDuration, expires)
// lifetime.Reset(expires)
// }
sess := &Session{
sid: sid,
provider: p,
values: values,
flashes: make(map[string]*flashMessage),
lifetime: lifetime,
}
return sess
}
func (p *provider) loadSessionFromDB(sid string) (Store, LifeTime) {
var store Store
var lifetime LifeTime
firstValidIdx := 1
for i, n := 0, len(p.databases); i < n; i++ {
storeDB := p.databases[i].Load(sid)
if storeDB.Lifetime.HasExpired() { // if expired then skip this db
firstValidIdx++
continue
}
if lifetime.IsZero() {
// update the lifetime to the most valid
lifetime = storeDB.Lifetime
}
if n == firstValidIdx {
// if one database then set the store as it is
store = storeDB.Values
} else {
// else append this database's key-value pairs
// to the store
storeDB.Values.Visit(func(key string, value interface{}) {
store.Set(key, value)
})
}
}
// Note: if one database and it's being expired then the lifetime will be zero(unlimited)
// this by itself is wrong but on the `newSession` we make check of this case too and update the lifetime
// if the configuration has expiration registered.
/// TODO: bug on destroy doesn't being remove the file
// we will have to see it, it's not db's problem it's here on provider destroy or lifetime onExpire.
return store, lifetime
}
// Init creates the session and returns it
func (p *provider) Init(sid string, expires time.Duration) *Session {
newSession := p.newSession(sid, expires)
p.mu.Lock()
p.sessions[sid] = newSession
p.mu.Unlock()
return newSession
}
// UpdateExpiration update expire date of a session.
// if expires > 0 then it updates the destroy task.
// if expires <=0 then it does nothing, to destroy a session call the `Destroy` func instead.
func (p *provider) UpdateExpiration(sid string, expires time.Duration) bool {
if expires <= 0 {
return false
}
p.mu.Lock()
sess, found := p.sessions[sid]
p.mu.Unlock()
if !found {
return false
}
sess.lifetime.Shift(expires)
return true
}
// Read returns the store which sid parameter belongs
func (p *provider) Read(sid string, expires time.Duration) *Session {
p.mu.Lock()
if sess, found := p.sessions[sid]; found {
sess.runFlashGC() // run the flash messages GC, new request here of existing session
p.mu.Unlock()
return sess
}
p.mu.Unlock()
return p.Init(sid, expires) // if not found create new
}
// Destroy destroys the session, removes all sessions and flash values,
// the session itself and updates the registered session databases,
// this called from sessionManager which removes the client's cookie also.
func (p *provider) Destroy(sid string) {
p.mu.Lock()
if sess, found := p.sessions[sid]; found {
p.deleteSession(sess)
}
p.mu.Unlock()
}
// DestroyAll removes all sessions
// from the server-side memory (and database if registered).
// Client's session cookie will still exist but it will be reseted on the next request.
func (p *provider) DestroyAll() {
p.mu.Lock()
for _, sess := range p.sessions {
p.deleteSession(sess)
}
p.mu.Unlock()
}
func (p *provider) deleteSession(sess *Session) {
delete(p.sessions, sess.sid)
syncDatabases(p.databases, acquireSyncPayload(sess, ActionDestroy))
}