fix: Ensure that messages that are in pending batches for an ordering key are canceled when a previous publish for the ordering keys fails (#366)

* feat: Add flow control support to publisher

* make suggested fixes

* chore: Remove note that ordering keys requires enablements.

* feat: Add support for server-side flow control

* Revert "chore: Remove note that ordering keys requires enablements."

This reverts commit 9c113c3.

* fix: Fix import order

* fix: Make error message more clear about where ordering must be enabled when publishing.

* fix: Ensure that messages that are in pending batches for an ordering key are canceled when a previous publish for the ordering keys fails.

Author: kamalaboulhosn

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

@@ -256,6 +256,11 @@ public ApiFuture<String> publish(PubsubMessage message) {
     List<OutstandingBatch> batchesToSend;
     messagesBatchLock.lock();
     try {
+      if (sequentialExecutor.keyHasError(orderingKey)) {
+        outstandingPublish.publishResult.setException(
+            SequentialExecutorService.CallbackExecutor.CANCELLATION_EXCEPTION);
+        return outstandingPublish.publishResult;
+      }
       MessagesBatch messagesBatch = messagesBatches.get(orderingKey);
       if (messagesBatch == null) {
         messagesBatch = new MessagesBatch(batchingSettings, orderingKey);
@@ -462,6 +467,21 @@ public void onSuccess(PublishResponse result) {
           @Override
           public void onFailure(Throwable t) {
             try {
+              if (outstandingBatch.orderingKey != null && !outstandingBatch.orderingKey.isEmpty()) {
+                messagesBatchLock.lock();
+                try {
+                  MessagesBatch messagesBatch = messagesBatches.get(outstandingBatch.orderingKey);
+                  if (messagesBatch != null) {
+                    for (OutstandingPublish outstanding : messagesBatch.messages) {
+                      outstanding.publishResult.setException(
+                          SequentialExecutorService.CallbackExecutor.CANCELLATION_EXCEPTION);
+                    }
+                    messagesBatches.remove(outstandingBatch.orderingKey);
+                  }
+                } finally {
+                  messagesBatchLock.unlock();
+                }
+              }
               outstandingBatch.onFailure(t);
             } finally {
               messagesWaiter.incrementPendingCount(-outstandingBatch.size());

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

@@ -243,6 +243,10 @@ public void cancel(Throwable e) {
       return future;
     }
 
+    boolean keyHasError(String key) {
+      return keysWithErrors.contains(key);
+    }
+
     void resumePublish(String key) {
       keysWithErrors.remove(key);
     }

google-cloud-pubsub/src/test/java/com/google/cloud/pubsub/v1/PublisherImplTest.java

@@ -566,6 +566,57 @@ public void testResumePublish() throws Exception {
     shutdownTestPublisher(publisher);
   }
 
+  @Test
+  public void testPublishThrowExceptionForUnsubmittedOrderingKeyMessage() throws Exception {
+    Publisher publisher =
+        getTestPublisherBuilder()
+            .setExecutorProvider(SINGLE_THREAD_EXECUTOR)
+            .setBatchingSettings(
+                Publisher.Builder.DEFAULT_BATCHING_SETTINGS
+                    .toBuilder()
+                    .setElementCountThreshold(2L)
+                    .setDelayThreshold(Duration.ofSeconds(500))
+                    .build())
+            .setEnableMessageOrdering(true)
+            .build();
+
+    // Send two messages that will fulfill the first batch, which will return a failure.
+    testPublisherServiceImpl.addPublishError(new StatusException(Status.INVALID_ARGUMENT));
+    ApiFuture<String> publishFuture1 = sendTestMessageWithOrderingKey(publisher, "A", "a");
+    ApiFuture<String> publishFuture2 = sendTestMessageWithOrderingKey(publisher, "B", "a");
+
+    // A third message will fail because the first attempt to publish failed.
+    ApiFuture<String> publishFuture3 = sendTestMessageWithOrderingKey(publisher, "C", "a");
+
+    try {
+      publishFuture1.get();
+      fail("Should have failed.");
+    } catch (ExecutionException e) {
+    }
+
+    try {
+      publishFuture2.get();
+      fail("Should have failed.");
+    } catch (ExecutionException e) {
+    }
+
+    try {
+      publishFuture3.get();
+      fail("Should have failed.");
+    } catch (ExecutionException e) {
+      assertEquals(SequentialExecutorService.CallbackExecutor.CANCELLATION_EXCEPTION, e.getCause());
+    }
+
+    // A subsequent attempt fails immediately.
+    ApiFuture<String> publishFuture4 = sendTestMessageWithOrderingKey(publisher, "D", "a");
+    try {
+      publishFuture4.get();
+      fail("Should have failed.");
+    } catch (ExecutionException e) {
+      assertEquals(SequentialExecutorService.CallbackExecutor.CANCELLATION_EXCEPTION, e.getCause());
+    }
+  }
+
   private ApiFuture<String> sendTestMessageWithOrderingKey(
       Publisher publisher, String data, String orderingKey) {
     return publisher.publish(