Clean up on exception while chunking XContent (#92024)

If serializing a chunk throws an exception, we must clean up the chunk
before propagating the exception.

Author: DaveCTurner

docs/changelog/92024.yaml

@@ -0,0 +1,5 @@
+pr: 92024
+summary: Clean up on exception while chunking XContent
+area: Network
+type: bug
+issues: []

server/src/main/java/org/elasticsearch/rest/ChunkedRestResponseBody.java

@@ -14,6 +14,7 @@
 import org.elasticsearch.common.recycler.Recycler;
 import org.elasticsearch.common.xcontent.ChunkedToXContent;
 import org.elasticsearch.core.IOUtils;
+import org.elasticsearch.core.Releasables;
 import org.elasticsearch.core.Streams;
 import org.elasticsearch.xcontent.ToXContent;
 import org.elasticsearch.xcontent.XContentBuilder;
@@ -92,20 +93,32 @@ public boolean isDone() {
 
             @Override
             public ReleasableBytesReference encodeChunk(int sizeHint, Recycler<BytesRef> recycler) throws IOException {
-                final RecyclerBytesStreamOutput chunkStream = new RecyclerBytesStreamOutput(recycler);
-                assert this.target == null;
-                this.target = chunkStream;
-                while (serialization.hasNext()) {
-                    serialization.next().toXContent(builder, params);
-                    if (chunkStream.size() >= sizeHint) {
-                        break;
+                try {
+                    final RecyclerBytesStreamOutput chunkStream = new RecyclerBytesStreamOutput(recycler);
+                    assert target == null;
+                    target = chunkStream;
+                    while (serialization.hasNext()) {
+                        serialization.next().toXContent(builder, params);
+                        if (chunkStream.size() >= sizeHint) {
+                            break;
+                        }
+                    }
+                    if (serialization.hasNext() == false) {
+                        builder.close();
+                    }
+                    final var result = new ReleasableBytesReference(
+                        chunkStream.bytes(),
+                        () -> Releasables.closeExpectNoException(chunkStream)
+                    );
+                    target = null;
+                    return result;
+                } finally {
+                    if (target != null) {
+                        assert false : "failure encoding chunk";
+                        IOUtils.closeWhileHandlingException(target);
+                        target = null;
                     }
                 }
-                if (serialization.hasNext() == false) {
-                    builder.close();
-                }
-                this.target = null;
-                return new ReleasableBytesReference(chunkStream.bytes(), () -> IOUtils.closeWhileHandlingException(chunkStream));
             }
 
             @Override