[GitHub] [iceberg] hililiwei commented on a diff in pull request #6299: Flink: support split discovery throttling for streaming read

[GitBox <gi...@apache.org>]

hililiwei commented on code in PR #6299:
URL: https://github.com/apache/iceberg/pull/6299#discussion_r1035451563


##########
flink/v1.16/flink/src/main/java/org/apache/iceberg/flink/source/enumerator/EnumerationHistory.java:
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@@ -0,0 +1,58 @@
+/*
+ * 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.iceberg.flink.source.enumerator;
+
+import javax.annotation.concurrent.ThreadSafe;
+import org.apache.flink.calcite.shaded.com.google.common.collect.EvictingQueue;
+
+/**
+ * This enumeration history is used for split discovery throttling. It wraps Guava {@link
+ * EvictingQueue} to provide thread safety.
+ */
+@ThreadSafe
+class EnumerationHistory {
+
+  // EvictingQueue is not thread safe.
+  private final EvictingQueue<Integer> enumerationSplitCountHistory;
+
+  EnumerationHistory(int maxHistorySize) {
+    this.enumerationSplitCountHistory = EvictingQueue.create(maxHistorySize);
+  }
+
+  /** Add the split count from the last enumeration result. */
+  synchronized void add(int splitCount) {
+    enumerationSplitCountHistory.add(splitCount);
+  }
+
+  /** @return true if split discovery should pause because assigner has too many splits already. */
+  synchronized boolean shouldPauseSplitDiscovery(int pendingSplitCountFromAssigner) {
+    if (enumerationSplitCountHistory.remainingCapacity() > 0) {
+      // only check throttling when full history is obtained.

Review Comment:
   I prefer the current no-checkpoint approach. To some extent, an empty history seems to be beneficial for quickly processing the backlog of data when the application restarts?
   
   



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