open-consul/agent/consul/session_ttl.go

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package consul
import (
"fmt"
"time"
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"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
)
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// initializeSessionTimers is used when a leader is newly elected to create
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// 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 {
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// 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 {
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if err := s.resetSessionTimer(session.ID, session); err != nil {
return err
}
}
return nil
}
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// 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 {
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// Fault the session in if not given
if session == nil {
state := s.fsm.State()
_, s, err := state.SessionGet(nil, id)
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if err != nil {
return err
}
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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
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switch session.TTL {
case "", "0", "0s", "0m", "0h":
return nil
}
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// 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)
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return nil
}
func (s *Server) createSessionTimer(id string, ttl time.Duration) {
// Reset the session timer
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// 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) })
}
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// 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())
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// Clear the session timer
s.sessionTimers.Del(id)
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// 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
}
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s.logger.Printf("[ERR] consul.session: Invalidation failed: %v", err)
time.Sleep((1 << attempt) * invalidateRetryBase)
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}
s.logger.Printf("[ERR] consul.session: maximum revoke attempts reached for session: %s", id)
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}
// 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
}
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// 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()
}
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// 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()))
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case <-s.shutdownCh:
return
}
}
}