Less bespoke signal handling

Use signal.NotifyContext() instead of creating our own go routine
checking for signals and closing a custom channel.

pkg/runner/runner.go

@@ -321,7 +321,7 @@ timerLoop:
 					}
 				}
 			}
-		case <-edm.stop:
+		case <-edm.ctx.Done():
 			break timerLoop
 		}
 	}
@@ -546,6 +546,7 @@ func Run() {
 		logger.Error("unable to init edm", "error", err)
 		os.Exit(1)
 	}
+	defer edm.stop()
 
 	viperNotifyCh := make(chan fsnotify.Event)
 
@@ -644,16 +645,6 @@ func Run() {
 		os.Exit(1)
 	}
 
-	// Exit gracefully on SIGINT or SIGTERM
-	go func() {
-		sigs := make(chan os.Signal, 1)
-		signal.Notify(sigs, os.Interrupt, syscall.SIGTERM)
-		<-sigs
-
-		// We received a signal, tell runMinimiser() to stop
-		close(edm.stop)
-	}()
-
 	metricsServer := &http.Server{
 		Addr:           "127.0.0.1:2112",
 		ReadTimeout:    10 * time.Second,
@@ -797,9 +788,10 @@ type dnstapMinimiser struct {
 	newQnameDiscarded       prometheus.Counter
 	seenQnameLRUEvicted     prometheus.Counter
 	newQnameChannelLen      prometheus.Gauge
-	stop                    chan struct{} // close this channel to gracefully stop runMinimiser()
-	debug                   bool          // if we should print debug messages during operation
-	mutex                   sync.RWMutex  // Mutex for protecting updates to fields at runtime
+	ctx                     context.Context
+	stop                    context.CancelFunc // call this to gracefully stop runMinimiser()
+	debug                   bool               // if we should print debug messages during operation
+	mutex                   sync.RWMutex       // Mutex for protecting updates to fields at runtime
 	sessionWriterCh         chan *prevSessions
 	histogramWriterCh       chan *wellKnownDomainsData
 	newQnamePublisherCh     chan *protocols.EventsMqttMessageNewQnameJson
@@ -833,6 +825,9 @@ func newDnstapMinimiser(logger *slog.Logger, cryptopanKey string, cryptopanSalt
 		return nil, fmt.Errorf("newDnstapMinimiser: %w", err)
 	}
 
+	// Exit gracefully on SIGINT or SIGTERM
+	edm.ctx, edm.stop = signal.NotifyContext(context.Background(), os.Interrupt, syscall.SIGTERM)
+
 	// Use separate prometheus registry for each edm instance, otherwise
 	// trying to run tests where each test do their own call to
 	// newDnstapMinimiser() will panic:
@@ -882,7 +877,6 @@ func newDnstapMinimiser(logger *slog.Logger, cryptopanKey string, cryptopanSalt
 	})
 
 	edm.promReg = promReg
-	edm.stop = make(chan struct{})
 	// Size 32 matches unexported "const outputChannelSize = 32" in
 	// https://github.com/dnstap/golang-dnstap/blob/master/dnstap.go
 	edm.inputChannel = make(chan []byte, 32)
@@ -1152,7 +1146,7 @@ func (edm *dnstapMinimiser) qnameSeen(msg *dns.Msg, seenQnameLRU *lru.Cache[stri
 
 // runMinimiser reads frames from the inputChannel, doing any modifications and
 // then passes them on to a dnstap.Output. To gracefully stop
-// runMinimiser() you need to close the edm.stop channel.
+// runMinimiser() you can call edm.stop().
 func (edm *dnstapMinimiser) runMinimiser(minimiserID int, wg *sync.WaitGroup, dawgFile string, seenQnameLRU *lru.Cache[string, struct{}], pdb *pebble.DB, newQnameBuffer int, disableSessionFiles bool, debugDnstapFile *os.File, disableHistogramSender bool, labelLimit int, wkdTracker *wellKnownDomainsTracker) {
 	defer wg.Done()
 
@@ -1246,7 +1240,7 @@ minimiserLoop:
 				session := edm.newSession(dt, msg, isQuery, labelLimit, timestamp)
 				edm.sessionCollectorCh <- session
 			}
-		case <-edm.stop:
+		case <-edm.ctx.Done():
 			break minimiserLoop
 		}
 	}
@@ -1486,7 +1480,7 @@ timerLoop:
 					}
 				}
 			}
-		case <-edm.stop:
+		case <-edm.ctx.Done():
 			break timerLoop
 		}
 	}