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package idle
import (
"net"
"net/http"
"sync"
"time"
"github.com/sirupsen/logrus"
)
// Tracker holds the state for the server's idle tracking
type Tracker struct {
// Duration is the API idle window
Duration time.Duration
hijacked int // count of active connections managed by handlers
managed map[net.Conn]struct{} // set of active connections managed by http package
mux sync.Mutex // protect managed map
timer *time.Timer
total int // total number of connections made to this server instance
}
// NewTracker creates and initializes a new Tracker object
// For best behavior, duration should be 2x http idle connection timeout
func NewTracker(idle time.Duration) *Tracker {
return &Tracker{
managed: make(map[net.Conn]struct{}),
Duration: idle,
timer: time.NewTimer(idle),
}
}
// ConnState is called on HTTP connection state changes.
// - Once StateHijacked, StateClose is _NOT_ called on that connection
// - There are two "idle" timeouts, the http idle connection (not to be confused with the TCP/IP idle socket timeout)
// and the API idle window. The caller should set the http idle timeout to 2x the time provided to NewTacker() which
// is the API idle window.
func (t *Tracker) ConnState(conn net.Conn, state http.ConnState) {
t.mux.Lock()
defer t.mux.Unlock()
logrus.Debugf("IdleTracker %p:%v %dm+%dh/%dt connection(s)", conn, state, len(t.managed), t.hijacked, t.TotalConnections())
switch state {
case http.StateNew, http.StateActive:
// stop the API timer when the server transitions any connection to an "active" state
t.managed[conn] = struct{}{}
t.timer.Stop()
t.total++
case http.StateHijacked:
// hijacked connections should call Close() when finished.
// Note: If a handler hijack's a connection and then doesn't Close() it,
// the API timer will not fire and the server will _NOT_ timeout.
delete(t.managed, conn)
t.hijacked++
case http.StateIdle:
// When any connection goes into the http idle state, we know:
// - we have an active connection
// - the API timer should not be counting down (See case StateNew/StateActive)
break
case http.StateClosed:
oldActive := t.ActiveConnections()
// Either the server or a hijacking handler has closed the http connection to a client
if _, found := t.managed[conn]; found {
delete(t.managed, conn)
} else {
t.hijacked-- // guarded by t.mux above
}
// Transitioned from any "active" connection to no connections
if oldActive > 0 && t.ActiveConnections() == 0 {
t.timer.Stop() // See library source for Reset() issues and why they are not fixed
t.timer.Reset(t.Duration) // Restart the API window timer
}
}
}
// Close is used to update Tracker that a StateHijacked connection has been closed by handler (StateClosed)
func (t *Tracker) Close() {
t.ConnState(nil, http.StateClosed)
}
// ActiveConnections returns the number of current managed or StateHijacked connections
func (t *Tracker) ActiveConnections() int {
return len(t.managed) + t.hijacked
}
// TotalConnections returns total number of connections made to this instance of the service
func (t *Tracker) TotalConnections() int {
return t.total
}
// Done is called when idle timer has expired
func (t *Tracker) Done() <-chan time.Time {
return t.timer.C
}
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