samples: exit early if no messages are returned (#989)

* samples: exit early if no messages are pulled * address kurtis's comments * update comment
googleapis · Feb 3, 2022 · ab828a0 · ab828a0
1 parent 9a1cc0e
commit ab828a0
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Showing 2 changed files with 16 additions and 4 deletions.
diff --git a/samples/snippets/src/main/java/pubsub/SubscribeSyncExample.java b/samples/snippets/src/main/java/pubsub/SubscribeSyncExample.java
@@ -60,12 +60,21 @@ public static void subscribeSyncExample(
 
       // Use pullCallable().futureCall to asynchronously perform this operation.
       PullResponse pullResponse = subscriber.pullCallable().call(pullRequest);
+
+      // Stop the program if the pull response is empty to avoid acknowledging
+      // an empty list of ack IDs.
+      if (pullResponse.getReceivedMessagesList().isEmpty()) {
+        System.out.println("No message was pulled. Exiting.");
+        return;
+      }
+
       List<String> ackIds = new ArrayList<>();
       for (ReceivedMessage message : pullResponse.getReceivedMessagesList()) {
         // Handle received message
         // ...
         ackIds.add(message.getAckId());
       }
+
       // Acknowledge received messages.
       AcknowledgeRequest acknowledgeRequest =
           AcknowledgeRequest.newBuilder()

diff --git a/samples/snippets/src/main/java/pubsub/SubscribeSyncWithLeaseExample.java b/samples/snippets/src/main/java/pubsub/SubscribeSyncWithLeaseExample.java
@@ -38,9 +38,6 @@ public static void main(String... args) throws Exception {
     String subscriptionId = "your-subscription-id";
     Integer numOfMessages = 10;
 
-    projectId = "tz-playground-bigdata";
-    subscriptionId = "uno";
-
     subscribeSyncWithLeaseExample(projectId, subscriptionId, numOfMessages);
   }
 
@@ -68,8 +65,14 @@ public static void subscribeSyncWithLeaseExample(
       // Use pullCallable().futureCall to asynchronously perform this operation.
       PullResponse pullResponse = subscriber.pullCallable().call(pullRequest);
 
-      List<String> ackIds = new ArrayList<>();
+      // Stop the program if the pull response is empty to avoid acknowledging
+      // an empty list of ack IDs.
+      if (pullResponse.getReceivedMessagesList().isEmpty()) {
+        System.out.println("No message was pulled. Exiting.");
+        return;
+      }
 
+      List<String> ackIds = new ArrayList<>();
       for (ReceivedMessage message : pullResponse.getReceivedMessagesList()) {
         ackIds.add(message.getAckId());