[GitHub] [flink] StephanEwen commented on a change in pull request #13784: [FLINK-19698][connectors/common] API improvements to the Sources.

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StephanEwen commented on a change in pull request #13784:
URL: https://github.com/apache/flink/pull/13784#discussion_r513286480



##########
File path: flink-core/src/main/java/org/apache/flink/util/ExceptionUtils.java
##########
@@ -565,6 +565,20 @@ else if (t instanceof Error) {
 		return Optional.empty();
 	}
 
+	/**
+	 * Find the root cause of the given throwable chain.
+	 *
+	 * @param throwable the throwable chain to check.
+	 * @return the root cause of the throwable chain.
+	 */
+	public static Throwable findRootCause(Throwable throwable) {

Review comment:
       I think this needs an extra check against cyclic cause chains, which are possible and nasty.
   
   We previously used the Apache Commons Lang for that: https://github.com/apache/flink/blob/master/flink-runtime/src/test/java/org/apache/flink/runtime/blob/BlobCacheGetTest.java#L597
   
   I think at the very least, we need a set to check duplicates and stop traversing once we see an exception we saw before.

##########
File path: flink-core/src/main/java/org/apache/flink/api/common/state/CheckpointListener.java
##########
@@ -0,0 +1,51 @@
+/*
+ Licensed to the Apache Software Foundation (ASF) under one

Review comment:
       Nit: The header here uses a different style than the rest of the code (other files have * at every line start).

##########
File path: flink-runtime/src/main/java/org/apache/flink/runtime/state/CheckpointListener.java
##########
@@ -1,19 +1,19 @@
 /*
- * 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.
+ Licensed to the Apache Software Foundation (ASF) under one

Review comment:
       Nit: The header here uses a different style than the rest of the code (other files have * at every line start).




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