From 4a0ef1f834c841af645472aa8badd23350409f5a Mon Sep 17 00:00:00 2001
From: Jon Chambers <jon@signal.org>
Date: Thu, 4 Aug 2022 10:33:19 -0400
Subject: [PATCH] Measure the time taken to send APNs push notifications

---
 .../textsecuregcm/push/APNSender.java             | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/service/src/main/java/org/whispersystems/textsecuregcm/push/APNSender.java b/service/src/main/java/org/whispersystems/textsecuregcm/push/APNSender.java
index 24813ffb7..70c994c52 100644
--- a/service/src/main/java/org/whispersystems/textsecuregcm/push/APNSender.java
+++ b/service/src/main/java/org/whispersystems/textsecuregcm/push/APNSender.java
@@ -17,11 +17,16 @@ import java.io.ByteArrayInputStream;
 import java.io.IOException;
 import java.security.InvalidKeyException;
 import java.security.NoSuchAlgorithmException;
+import java.time.Duration;
 import java.time.Instant;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.ExecutorService;
+import io.micrometer.core.instrument.Metrics;
+import io.micrometer.core.instrument.Timer;
 import org.whispersystems.textsecuregcm.configuration.ApnConfiguration;
 
+import static org.whispersystems.textsecuregcm.metrics.MetricsUtil.name;
+
 public class APNSender implements Managed, PushNotificationSender {
 
   private final ExecutorService executor;
@@ -45,6 +50,8 @@ public class APNSender implements Managed, PushNotificationSender {
 
   private static final String APNS_CA_FILENAME = "apns-certificates.pem";
 
+  private static final Timer SEND_NOTIFICATION_TIMER = Metrics.timer(name(APNSender.class, "sendNotification"));
+
   public APNSender(ExecutorService executor, ApnConfiguration configuration)
       throws IOException, NoSuchAlgorithmException, InvalidKeyException
   {
@@ -95,6 +102,8 @@ public class APNSender implements Managed, PushNotificationSender {
         (notification.notificationType() == PushNotification.NotificationType.NOTIFICATION && !isVoip)
             ? "incoming-message" : null;
 
+    final Instant start = Instant.now();
+
     return apnsClient.sendNotification(new SimpleApnsPushNotification(notification.deviceToken(),
         topic,
         payload,
@@ -102,6 +111,12 @@ public class APNSender implements Managed, PushNotificationSender {
         DeliveryPriority.IMMEDIATE,
         isVoip ? PushType.VOIP : PushType.ALERT,
         collapseId))
+        .whenComplete((response, throwable) -> {
+          // Note that we deliberately run this small bit of non-blocking measurement on the "send notification" thread
+          // to avoid any measurement noise that could arise from dispatching to another executor and waiting in its
+          // queue
+          SEND_NOTIFICATION_TIMER.record(Duration.between(start, Instant.now()));
+        })
         .thenApplyAsync(response -> {
           final boolean accepted;
           final String rejectionReason;