--- a/calsync/main.go	Fri Sep 06 18:24:38 2024 -0700
+++ b/calsync/main.go	Fri Sep 06 18:25:32 2024 -0700
@@ -28,6 +28,8 @@
 	"github.com/gorilla/mux"
 )
 
+const startupJitter = 0 * time.Second
+
 func main() {
 	startLogging()
 	ctx := context.Background()
@@ -55,7 +57,7 @@
 
 	initialSyncBack := (7 * 24) * time.Hour
 	initialSyncAhead := (14 * 24) * time.Hour
-	err = updateMongoEventsToMatchGoogleForever(mc, gc, initialSyncBack, initialSyncAhead, notifications)
+	err = updateMongoEventsToMatchGoogleForever(mc, gc, initialSyncBack, initialSyncAhead, notifications, startupJitter)
 	if err != nil {
 		log.Fatal(err)
 	}

--- a/calsync/sync_event.go	Fri Sep 06 18:24:38 2024 -0700
+++ b/calsync/sync_event.go	Fri Sep 06 18:25:32 2024 -0700
@@ -16,6 +16,9 @@
 // Time that we'll still accept the old watchId after we've registered a new one.
 const grace = 1 * time.Minute
 
+// How often to renew watches (roughly).
+const watchLifetime = time.Duration(120) * time.Minute
+
 // Each calendar syncs like this:
 //  1. Full sync of events taking place between `now-initialSyncBack` to `now+initialSyncAhead`.
 //  2. Garbage-collect all events last-modified before `now-initialSyncBack`
@@ -26,6 +29,7 @@
 	initialSyncBack time.Duration,
 	initialSyncAhead time.Duration,
 	router *notificationrouter.NotificationRouter,
+	startupJitter time.Duration,
 ) error {
 	log.Println("starting updateMongoEventsToMatchGoogleForever")
 
@@ -43,7 +47,7 @@
 	for _, cal := range cals {
 		rd := newCalEventsReader(mc, gc, router, cal, initialSyncT1, initialSyncT2)
 		go func() {
-			err := rd.watchForUpdates()
+			err := rd.watchForUpdates(startupJitter)
 			if err != nil {
 				log.Println("ERROR", M.Prefix(rd.cal), "watchForUpdates: ", err, "(aborting this calendar)")
 			}
@@ -71,16 +75,14 @@
 	return &calEventsReader{mc, gc, router, cal, t1, t2, ""}
 }
 
-func (r *calEventsReader) watchForUpdates() error {
-	r.watchForUpdatesJitteredStartup()
+func (r *calEventsReader) watchForUpdates(startupJitter time.Duration) error {
+	r.watchForUpdatesJitteredStartup(startupJitter)
 
 	err := r.updateInitialRange()
 	if err != nil {
 		return err
 	}
 
-	watchLifetime := time.Duration(3) * time.Minute
-
 	syncFunc := notificationrouter.SyncFunc(func() {
 		err := r.sync()
 		if err != nil {
@@ -91,8 +93,8 @@
 	return nil
 }
 
-func (r *calEventsReader) watchForUpdatesJitteredStartup() {
-	jitteredStartup := time.Duration(rand.Int()%30) * time.Second
+func (r *calEventsReader) watchForUpdatesJitteredStartup(startupJitter time.Duration) {
+	jitteredStartup := time.Duration(startupJitter.Seconds()*rand.Float64()) * time.Second
 	log.Println(M.Prefix(r.cal), "watchForEvents starting in", jitteredStartup)
 	time.Sleep(jitteredStartup)
 }