fix: update MessageDispatcher to not extend deadlines of messages which arrive early to 60s

google-cloud-pubsub/src/main/java/com/google/cloud/pubsub/v1/MessageDispatcher.java

@@ -82,9 +82,10 @@ class MessageDispatcher {
   private final LinkedBlockingQueue<String> pendingNacks = new LinkedBlockingQueue<>();
   private final LinkedBlockingQueue<String> pendingReceipts = new LinkedBlockingQueue<>();
 
-  // The deadline should be set before use. Here, set it to something unreasonable,
-  // so we fail loudly if we mess up.
-  private final AtomicInteger messageDeadlineSeconds = new AtomicInteger(60);
+  // Start the deadline at the minimum ack deadline so messages which arrive before this is
+  // updated will not have a long ack deadline.
+  private final AtomicInteger messageDeadlineSeconds =
+      new AtomicInteger(Subscriber.MIN_ACK_DEADLINE_SECONDS);
   private final AtomicBoolean extendDeadline = new AtomicBoolean(true);
   private final Lock jobLock;
   private ScheduledFuture<?> backgroundJob;

google-cloud-pubsub/src/main/java/com/google/cloud/pubsub/v1/Subscriber.java

@@ -184,9 +184,9 @@ public Void apply(UnaryCallSettings.Builder<?, ?> settingsBuilder) {
     streamingSubscriberConnections = new ArrayList<StreamingSubscriberConnection>(numPullers);
 
     // We regularly look up the distribution for a good subscription deadline.
-    // So we seed the distribution with something reasonable to start with.
+    // So we seed the distribution with the minimum value to start with.
     // Distribution is percentile-based, so this value will eventually lose importance.
-    ackLatencyDistribution.record(60);
+    ackLatencyDistribution.record(MIN_ACK_DEADLINE_SECONDS);
   }
 
   /**