Ensure BinaryData responses are durable in polling operations (Azure#36999)

Ensure BinaryData responses are durable in polling operations

Author: alzimmermsft

sdk/core/azure-core/src/main/java/com/azure/core/implementation/util/FluxByteBufferContent.java

@@ -18,7 +18,6 @@
 import java.util.Objects;
 import java.util.concurrent.atomic.AtomicReference;
 import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;
-import java.util.function.BiConsumer;
 
 /**
  * A {@link BinaryDataContent} implementation which is backed by a {@link Flux} of {@link ByteBuffer}.
@@ -125,31 +124,47 @@ public BinaryDataContent toReplayableContent() {
             return replayableContent;
         }
 
-        Flux<ByteBuffer> bufferedFlux = content
-            .map(buffer -> {
-                // deep copy direct buffers
-                ByteBuffer copy = ByteBuffer.allocate(buffer.remaining());
-                copy.put(buffer);
-                copy.flip();
-                return copy;
-            })
-            // collectList() uses ArrayList. We don't want to be bound by array capacity
-            // and we don't need random access.
-            .collect(LinkedList::new, (BiConsumer<LinkedList<ByteBuffer>, ByteBuffer>) LinkedList::add)
-            .cache()
-            .flatMapMany(
-                // Duplicate buffers on re-subscription.
-                listOfBuffers -> Flux.fromIterable(listOfBuffers).map(ByteBuffer::duplicate));
-        replayableContent = new FluxByteBufferContent(bufferedFlux, length, true);
-        cachedReplayableContent.set(replayableContent);
-        return replayableContent;
+        return bufferContent().map(bufferedData -> {
+            FluxByteBufferContent bufferedContent = new FluxByteBufferContent(Flux.fromIterable(bufferedData)
+                .map(ByteBuffer::duplicate), length, true);
+            cachedReplayableContent.set(bufferedContent);
+
+            return bufferedContent;
+        }).block();
     }
 
     @Override
     public Mono<BinaryDataContent> toReplayableContentAsync() {
-        return Mono.fromCallable(this::toReplayableContent);
+        if (isReplayable) {
+            return Mono.just(this);
+        }
+
+        FluxByteBufferContent replayableContent = cachedReplayableContent.get();
+        if (replayableContent != null) {
+            return Mono.just(replayableContent);
+        }
+
+        return bufferContent().cache().map(bufferedData -> {
+            Flux<ByteBuffer> bufferedFluxData = Flux.fromIterable(bufferedData).map(ByteBuffer::asReadOnlyBuffer);
+            FluxByteBufferContent bufferedBinaryDataContent = new FluxByteBufferContent(bufferedFluxData, length, true);
+            cachedReplayableContent.set(bufferedBinaryDataContent);
+
+            return bufferedBinaryDataContent;
+        });
     }
 
+    private Mono<LinkedList<ByteBuffer>> bufferContent() {
+        // collectList() uses ArrayList, we don't want to be bound by array capacity and don't need random access
+        return content.map(buffer -> {
+            // deep copy direct buffers
+            ByteBuffer copy = ByteBuffer.allocate(buffer.remaining());
+            copy.put(buffer);
+            copy.flip();
+            return copy;
+        }).collect(LinkedList::new, LinkedList::add);
+    }
+
+
     @Override
     public BinaryDataContentType getContentType() {
         return BinaryDataContentType.BINARY;

sdk/core/azure-core/src/main/java/com/azure/core/util/polling/implementation/PollingUtils.java

@@ -63,7 +63,7 @@ public static BinaryData serializeResponseSync(Object response, ObjectSerializer
     public static <T> Mono<T> deserializeResponse(BinaryData binaryData, ObjectSerializer serializer,
                                                   TypeReference<T> typeReference) {
         if (TypeUtil.isTypeOrSubTypeOf(BinaryData.class, typeReference.getJavaType())) {
-            return Mono.just((T) binaryData);
+            return (Mono<T>) binaryData.toReplayableBinaryDataAsync();
         } else {
             return binaryData.toObjectAsync(typeReference, serializer);
         }
@@ -83,7 +83,7 @@ public static <T> Mono<T> deserializeResponse(BinaryData binaryData, ObjectSeria
     public static <T> T deserializeResponseSync(BinaryData binaryData, ObjectSerializer serializer,
         TypeReference<T> typeReference) {
         if (TypeUtil.isTypeOrSubTypeOf(BinaryData.class, typeReference.getJavaType())) {
-            return (T) binaryData;
+            return (T) binaryData.toReplayableBinaryData();
         } else {
             return binaryData.toObject(typeReference, serializer);
         }

sdk/core/azure-core/src/test/java/com/azure/core/util/BinaryDataTest.java

@@ -57,6 +57,7 @@
 import java.util.List;
 import java.util.Objects;
 import java.util.UUID;
+import java.util.concurrent.ThreadLocalRandom;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.concurrent.atomic.AtomicLong;
@@ -68,6 +69,7 @@
 import static com.azure.core.CoreTestUtils.fillArray;
 import static com.azure.core.CoreTestUtils.readStream;
 import static com.azure.core.implementation.util.BinaryDataContent.STREAM_READ_SIZE;
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertInstanceOf;
@@ -1049,6 +1051,68 @@ public void binaryDataAsPropertyDeserialization() throws IOException {
         assertEquals(expected.getProperty().toString(), actual.getProperty().toString());
     }
 
+    @Test
+    public void emptyFluxByteBufferToReplayable() {
+        BinaryData binaryData = BinaryData.fromFlux(Flux.empty()).block();
+
+        BinaryData replayable = assertDoesNotThrow(() -> binaryData.toReplayableBinaryData());
+        assertEquals("", replayable.toString());
+    }
+
+    @Test
+    public void emptyFluxByteBufferToReplayableAsync() {
+        StepVerifier.create(BinaryData.fromFlux(Flux.empty())
+            .flatMap(BinaryData::toReplayableBinaryDataAsync))
+            .assertNext(replayable -> assertEquals("", replayable.toString()))
+            .verifyComplete();
+    }
+
+    /**
+     * Tests that {@link FluxByteBufferContent#toReplayableContent()} eagerly makes the {@link FluxByteBufferContent}
+     * replayable. Before, this method wouldn't make the content replayable until the return
+     * {@link FluxByteBufferContent} was consumed, which defeated the purpose of the method as the underlying data could
+     * be reclaimed or consumed before it was made replayable.
+     */
+    @Test
+    public void fluxByteBufferToReplayableEagerlyConvertsToReplayable() {
+        byte[] data = new byte[1024];
+        ThreadLocalRandom.current().nextBytes(data);
+        byte[] expectedData = CoreUtils.clone(data);
+
+        BinaryDataContent binaryDataContent = new FluxByteBufferContent(Flux.just(ByteBuffer.wrap(data)))
+            .toReplayableContent();
+
+        Arrays.fill(data, (byte) 0);
+
+        assertArraysEqual(expectedData, binaryDataContent.toBytes());
+    }
+
+    /**
+     * Tests that {@link FluxByteBufferContent} returned by {@link FluxByteBufferContent#toReplayableContentAsync()}
+     * won't attempt to access the original {@link Flux Flux<ByteBuffer>} as the initial duplicated is cached as a
+     * stream of {@link ByteBuffer ByteBuffers} that are shared to all subscribers, and duplicated in each subscription
+     * so that the underlying content cannot be modified.
+     */
+    @Test
+    public void multipleSubscriptionsToReplayableAsyncFluxByteBufferAreConsistent() {
+        byte[] data = new byte[1024];
+        ThreadLocalRandom.current().nextBytes(data);
+        byte[] expectedData = CoreUtils.clone(data);
+
+        Mono<BinaryDataContent> binaryDataContentMono = new FluxByteBufferContent(Flux.just(ByteBuffer.wrap(data)))
+            .toReplayableContentAsync();
+
+        StepVerifier.create(binaryDataContentMono)
+            .assertNext(binaryDataContent -> assertArraysEqual(expectedData, binaryDataContent.toBytes()))
+            .verifyComplete();
+
+        Arrays.fill(data, (byte) 0);
+
+        StepVerifier.create(binaryDataContentMono)
+            .assertNext(binaryDataContent -> assertArraysEqual(expectedData, binaryDataContent.toBytes()))
+            .verifyComplete();
+    }
+
     public static final class BinaryDataAsProperty {
         @JsonProperty("property")
         private BinaryData property;