package consul import ( "fmt" "time" "github.com/armon/go-metrics" "github.com/hashicorp/consul/agent/structs" ) const ( // maxInvalidateAttempts limits how many invalidate attempts are made maxInvalidateAttempts = 6 // invalidateRetryBase is a baseline retry time invalidateRetryBase = 10 * time.Second ) // initializeSessionTimers is used when a leader is newly elected to create // a new map to track session expiration and to reset all the timers from // the previously known set of timers. func (s *Server) initializeSessionTimers() error { // Scan all sessions and reset their timer state := s.fsm.State() _, sessions, err := state.SessionList(nil) if err != nil { return err } for _, session := range sessions { if err := s.resetSessionTimer(session.ID, session); err != nil { return err } } return nil } // resetSessionTimer is used to renew the TTL of a session. // This can be used for new sessions and existing ones. A session // will be faulted in if not given. func (s *Server) resetSessionTimer(id string, session *structs.Session) error { // Fault the session in if not given if session == nil { state := s.fsm.State() _, s, err := state.SessionGet(nil, id) if err != nil { return err } if s == nil { return fmt.Errorf("Session '%s' not found", id) } session = s } // Bail if the session has no TTL, fast-path some common inputs switch session.TTL { case "", "0", "0s", "0m", "0h": return nil } // Parse the TTL, and skip if zero time ttl, err := time.ParseDuration(session.TTL) if err != nil { return fmt.Errorf("Invalid Session TTL '%s': %v", session.TTL, err) } if ttl == 0 { return nil } s.createSessionTimer(session.ID, ttl) return nil } func (s *Server) createSessionTimer(id string, ttl time.Duration) { // Reset the session timer // Adjust the given TTL by the TTL multiplier. This is done // to give a client a grace period and to compensate for network // and processing delays. The contract is that a session is not expired // before the TTL, but there is no explicit promise about the upper // bound so this is allowable. ttl = ttl * structs.SessionTTLMultiplier s.sessionTimers.ResetOrCreate(id, ttl, func() { s.invalidateSession(id) }) } // invalidateSession is invoked when a session TTL is reached and we // need to invalidate the session. func (s *Server) invalidateSession(id string) { defer metrics.MeasureSince([]string{"session_ttl", "invalidate"}, time.Now()) // Clear the session timer s.sessionTimers.Del(id) // Create a session destroy request args := structs.SessionRequest{ Datacenter: s.config.Datacenter, Op: structs.SessionDestroy, Session: structs.Session{ ID: id, }, } // Retry with exponential backoff to invalidate the session for attempt := uint(0); attempt < maxInvalidateAttempts; attempt++ { _, err := s.raftApply(structs.SessionRequestType, args) if err == nil { s.logger.Printf("[DEBUG] consul.state: Session %s TTL expired", id) return } s.logger.Printf("[ERR] consul.session: Invalidation failed: %v", err) time.Sleep((1 << attempt) * invalidateRetryBase) } s.logger.Printf("[ERR] consul.session: maximum revoke attempts reached for session: %s", id) } // clearSessionTimer is used to clear the session time for // a single session. This is used when a session is destroyed // explicitly and no longer needed. func (s *Server) clearSessionTimer(id string) error { s.sessionTimers.Stop(id) return nil } // clearAllSessionTimers is used when a leader is stepping // down and we no longer need to track any session timers. func (s *Server) clearAllSessionTimers() { s.sessionTimers.StopAll() } // sessionStats is a long running routine used to capture // the number of active sessions being tracked func (s *Server) sessionStats() { for { select { case <-time.After(5 * time.Second): metrics.SetGauge([]string{"session_ttl", "active"}, float32(s.sessionTimers.Len())) case <-s.shutdownCh: return } } }