Github user pnowojski commented on a diff in the pull request:
https://github.com/apache/flink/pull/5400#discussion_r167537474
--- Diff:
flink-streaming-java/src/main/java/org/apache/flink/streaming/runtime/io/BufferBlocker.java
---
@@ -0,0 +1,61 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.flink.streaming.runtime.io;
+
+import org.apache.flink.annotation.Internal;
+import
org.apache.flink.runtime.io.network.partition.consumer.BufferOrEvent;
+
+import java.io.IOException;
+
+/**
+ * The buffer blocker takes the buffers and events from a data stream and
adds them in a sequence.
+ * After a number of elements have been added, the blocker can "roll
over": It presents the added
+ * elements as a readable sequence, and creates a new sequence.
+ */
+@Internal
+public interface BufferBlocker {
+
+ /**
+ * Adds a buffer or event to the blocker.
+ *
+ * @param boe The buffer or event to be added into the blocker.
+ */
+ void add(BufferOrEvent boe) throws IOException;
+
+ /**
+ * Starts a new sequence of buffers and event and returns the current
sequence of buffers for reading.
+ * This method returns {@code null}, if nothing was added since the
creation, or the last call to this method.
+ *
+ * @param newBuffer only works for {@link BufferSpiller} implements
currently.
--- End diff --
Java doc in this interface shouldn't mention implementation specific
details. On the other hand, this java doc doesn't explain what `newBuffer` is
doing and for this information one must check the `BufferSpiller`'s java doc
itself.
Can you add appropriate java doc here, or better add java doc to proposed
in the comment below two methods: `rollOverWithoutReusingResources()` and
`rollOverReusingResources()`. Comment in
`CachedBufferBlocker.java#rollOverReusingResources` should state that it is
never reusing resources and is defaulting to
`CachedBufferBlocker.java#rollOverWithoutReusingResources`
---
