From 36939dc4f93f237f031364c7dc32f4c0dbf56545 Mon Sep 17 00:00:00 2001
From: Arko Dasgupta <arkodg@users.noreply.github.com>
Date: Thu, 28 Nov 2024 20:31:52 -0800
Subject: [PATCH] use a waitGroup instead of an enabled channel in the status
 updater (#4809)

use a waitGroup instead of a channel in the status updater

* use a waitGroup to synchronize to the `Send` method that the
status updater is enabled and ready for updates

Signed-off-by: Arko Dasgupta <arko@tetrate.io>
---
 .../provider/kubernetes/status_updater.go     | 64 ++++++-------------
 1 file changed, 18 insertions(+), 46 deletions(-)

diff --git a/internal/provider/kubernetes/status_updater.go b/internal/provider/kubernetes/status_updater.go
index ee5cbce59d2..1bafe23668b 100644
--- a/internal/provider/kubernetes/status_updater.go
+++ b/internal/provider/kubernetes/status_updater.go
@@ -7,7 +7,7 @@ package kubernetes
 
 import (
 	"context"
-	"errors"
+	"sync"
 	"time"
 
 	"github.com/go-logr/logr"
@@ -57,26 +57,21 @@ func (m MutatorFunc) Mutate(old client.Object) client.Object {
 type UpdateHandler struct {
 	log           logr.Logger
 	client        client.Client
-	sendUpdates   chan struct{}
 	updateChannel chan Update
-	writer        *UpdateWriter
+	wg            *sync.WaitGroup
 }
 
 func NewUpdateHandler(log logr.Logger, client client.Client) *UpdateHandler {
-	sendUpdates := make(chan struct{})
-	updateChannel := make(chan Update, 100)
-	return &UpdateHandler{
+	u := &UpdateHandler{
 		log:           log,
 		client:        client,
-		sendUpdates:   sendUpdates,
-		updateChannel: updateChannel,
-		writer: &UpdateWriter{
-			log:                 log,
-			enabled:             sendUpdates,
-			updateChannel:       updateChannel,
-			eventsBeforeEnabled: make(chan Update, 1000),
-		},
+		updateChannel: make(chan Update, 1000),
+		wg:            new(sync.WaitGroup),
 	}
+
+	u.wg.Add(1)
+
+	return u
 }
 
 func (u *UpdateHandler) apply(update Update) {
@@ -140,8 +135,7 @@ func (u *UpdateHandler) Start(ctx context.Context) error {
 	defer u.log.Info("stopped status update handler")
 
 	// Enable Updaters to start sending updates to this handler.
-	close(u.sendUpdates)
-	u.writer.handleEventsReceivedBeforeEnabled()
+	u.wg.Done()
 
 	for {
 		select {
@@ -158,7 +152,10 @@ func (u *UpdateHandler) Start(ctx context.Context) error {
 
 // Writer retrieves the interface that should be used to write to the UpdateHandler.
 func (u *UpdateHandler) Writer() Updater {
-	return u.writer
+	return &UpdateWriter{
+		updateChannel: u.updateChannel,
+		wg:            u.wg,
+	}
 }
 
 // Updater describes an interface to send status updates somewhere.
@@ -168,40 +165,15 @@ type Updater interface {
 
 // UpdateWriter takes status updates and sends these to the UpdateHandler via a channel.
 type UpdateWriter struct {
-	log           logr.Logger
-	enabled       <-chan struct{}
 	updateChannel chan<- Update
-	// a temporary buffer to store events received before the Updater is enabled.
-	// These events will be sent to the update channel once the Updater is enabled.
-	eventsBeforeEnabled chan Update
+	wg            *sync.WaitGroup
 }
 
 // Send sends the given Update off to the update channel for writing by the UpdateHandler.
 func (u *UpdateWriter) Send(update Update) {
-	// Non-blocking receive to see if we should pass along update.
-	select {
-	case <-u.enabled:
-		u.updateChannel <- update
-	default:
-		if len(u.eventsBeforeEnabled) < cap(u.eventsBeforeEnabled) {
-			u.log.Info("received a status update while disabled, storing for later", "event", update.NamespacedName)
-			u.eventsBeforeEnabled <- update
-		} else {
-			// If the buffer is full, drop the event to avoid blocking the sender.
-			u.log.Error(errors.New("dropping status update, buffer full"), "event", update.NamespacedName)
-		}
-	}
-}
-
-// handleEventsReceivedBeforeEnabled sends the events received before the Updater was enabled to the update channel.
-func (u *UpdateWriter) handleEventsReceivedBeforeEnabled() {
-	go func() {
-		for e := range u.eventsBeforeEnabled {
-			u.log.Info("sending stored status update", "event", e.NamespacedName)
-			u.updateChannel <- e
-		}
-		close(u.eventsBeforeEnabled)
-	}()
+	// Wait until updater is ready
+	u.wg.Wait()
+	u.updateChannel <- update
 }
 
 // isStatusEqual checks if two objects have equivalent status.