log/sockstatlog: also shutdown the poll goroutine

Co-authored-by: Will Norris <will@tailscale.com>
Signed-off-by: Maisem Ali <maisem@tailscale.com>

log/sockstatlog/logger.go

@@ -5,6 +5,7 @@
 package sockstatlog
 
 import (
+	"context"
 	"encoding/json"
 	"io"
 	"os"
@@ -22,6 +23,9 @@
 
 // Logger logs statistics about network sockets.
 type Logger struct {
+	ctx      context.Context
+	cancelFn context.CancelFunc
+
 	ticker    time.Ticker
 	logf      logger.Logf
 	logbuffer *filch.Filch
@@ -63,7 +67,10 @@ func NewLogger(logdir string, logf logger.Logf) (*Logger, error) {
 		return nil, err
 	}
 
+	ctx, cancel := context.WithCancel(context.Background())
 	return &Logger{
+		ctx:       ctx,
+		cancelFn:  cancel,
 		ticker:    *time.NewTicker(pollPeriod),
 		logf:      logf,
 		logbuffer: filch,
@@ -83,32 +90,38 @@ func (l *Logger) poll() {
 	var lastTime time.Time
 
 	enc := json.NewEncoder(l.logbuffer)
-	for t := range l.ticker.C {
-		stats := sockstats.Get()
-		if lastStats != nil {
-			diffstats := delta(lastStats, stats)
-			if len(diffstats) > 0 {
-				e := event{
-					Time:     lastTime.UnixMilli(),
-					Duration: t.Sub(lastTime).Milliseconds(),
-					Stats:    diffstats,
-				}
-				if stats.CurrentInterfaceCellular {
-					e.IsCellularInterface = 1
-				}
-				if err := enc.Encode(e); err != nil {
-					l.logf("sockstatlog: error encoding log: %v", err)
+	for {
+		select {
+		case <-l.ctx.Done():
+			return
+		case t := <-l.ticker.C:
+			stats := sockstats.Get()
+			if lastStats != nil {
+				diffstats := delta(lastStats, stats)
+				if len(diffstats) > 0 {
+					e := event{
+						Time:     lastTime.UnixMilli(),
+						Duration: t.Sub(lastTime).Milliseconds(),
+						Stats:    diffstats,
+					}
+					if stats.CurrentInterfaceCellular {
+						e.IsCellularInterface = 1
+					}
+					if err := enc.Encode(e); err != nil {
+						l.logf("sockstatlog: error encoding log: %v", err)
+					}
 				}
 			}
+			lastTime = t
+			lastStats = stats
 		}
-		lastTime = t
-		lastStats = stats
 	}
 }
 
 func (l *Logger) Shutdown() {
 	l.ticker.Stop()
 	l.logbuffer.Close()
+	l.cancelFn()
 }
 
 // WriteLogs reads local logs, combining logs into events, and writes them to w.