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// Copyright 2016 Michal Witkowski. All Rights Reserved.
// See LICENSE for licensing terms.
package conntrack
import (
"fmt"
"net"
"sync"
"time"
"github.com/jpillora/backoff"
"golang.org/x/net/trace"
)
const (
defaultName = "default"
)
type listenerOpts struct {
name string
monitoring bool
tracing bool
tcpKeepAlive time.Duration
retryBackoff *backoff.Backoff
}
type listenerOpt func(*listenerOpts)
// TrackWithName sets the name of the Listener for use in tracking and monitoring.
func TrackWithName(name string) listenerOpt {
return func(opts *listenerOpts) {
opts.name = name
}
}
// TrackWithoutMonitoring turns *off* Prometheus monitoring for this listener.
func TrackWithoutMonitoring() listenerOpt {
return func(opts *listenerOpts) {
opts.monitoring = false
}
}
// TrackWithTracing turns *on* the /debug/events tracing of the live listener connections.
func TrackWithTracing() listenerOpt {
return func(opts *listenerOpts) {
opts.tracing = true
}
}
// TrackWithRetries enables retrying of temporary Accept() errors, with the given backoff between attempts.
// Concurrent accept calls that receive temporary errors have independent backoff scaling.
func TrackWithRetries(b backoff.Backoff) listenerOpt {
return func(opts *listenerOpts) {
opts.retryBackoff = &b
}
}
// TrackWithTcpKeepAlive makes sure that any `net.TCPConn` that get accepted have a keep-alive.
// This is useful for HTTP servers in order for, for example laptops, to not use up resources on the
// server while they don't utilise their connection.
// A value of 0 disables it.
func TrackWithTcpKeepAlive(keepalive time.Duration) listenerOpt {
return func(opts *listenerOpts) {
opts.tcpKeepAlive = keepalive
}
}
type connTrackListener struct {
net.Listener
opts *listenerOpts
}
// NewListener returns the given listener wrapped in connection tracking listener.
func NewListener(inner net.Listener, optFuncs ...listenerOpt) net.Listener {
opts := &listenerOpts{
name: defaultName,
monitoring: true,
tracing: false,
}
for _, f := range optFuncs {
f(opts)
}
if opts.monitoring {
preRegisterListenerMetrics(opts.name)
}
return &connTrackListener{
Listener: inner,
opts: opts,
}
}
func (ct *connTrackListener) Accept() (net.Conn, error) {
// TODO(mwitkow): Add monitoring of failed accept.
var (
conn net.Conn
err error
)
for attempt := 0; ; attempt++ {
conn, err = ct.Listener.Accept()
if err == nil || ct.opts.retryBackoff == nil {
break
}
if t, ok := err.(interface{ Temporary() bool }); !ok || !t.Temporary() {
break
}
time.Sleep(ct.opts.retryBackoff.ForAttempt(float64(attempt)))
}
if err != nil {
return nil, err
}
if tcpConn, ok := conn.(*net.TCPConn); ok && ct.opts.tcpKeepAlive > 0 {
tcpConn.SetKeepAlive(true)
tcpConn.SetKeepAlivePeriod(ct.opts.tcpKeepAlive)
}
return newServerConnTracker(conn, ct.opts), nil
}
type serverConnTracker struct {
net.Conn
opts *listenerOpts
event trace.EventLog
mu sync.Mutex
}
func newServerConnTracker(inner net.Conn, opts *listenerOpts) net.Conn {
tracker := &serverConnTracker{
Conn: inner,
opts: opts,
}
if opts.tracing {
tracker.event = trace.NewEventLog(fmt.Sprintf("net.ServerConn.%s", opts.name), fmt.Sprintf("%v", inner.RemoteAddr()))
tracker.event.Printf("accepted: %v -> %v", inner.RemoteAddr(), inner.LocalAddr())
}
if opts.monitoring {
reportListenerConnAccepted(opts.name)
}
return tracker
}
func (ct *serverConnTracker) Close() error {
err := ct.Conn.Close()
ct.mu.Lock()
if ct.event != nil {
if err != nil {
ct.event.Errorf("failed closing: %v", err)
} else {
ct.event.Printf("closing")
}
ct.event.Finish()
ct.event = nil
}
ct.mu.Unlock()
if ct.opts.monitoring {
reportListenerConnClosed(ct.opts.name)
}
return err
}
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