[GitHub] [flink] AHeise commented on a change in pull request #13545: [FLINK-19486] Make "Unexpected State Handle" Exception more helpful

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AHeise commented on a change in pull request #13545:
URL: https://github.com/apache/flink/pull/13545#discussion_r500249333



##########
File path: flink-runtime/src/main/java/org/apache/flink/runtime/state/UnexpectedStateHandleException.java
##########
@@ -0,0 +1,46 @@
+/*
+ * 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.runtime.state;
+
+import org.apache.flink.shaded.guava18.com.google.common.base.Joiner;
+
+/**
+ * Signals that an operation did not get the type of {@link StateObject} that was expected. This can
+ * mostly happen when a different {@link StateBackend} from the one that was used for taking a
+ * checkpoint/savepoint is used when restoring.
+ */
+public class UnexpectedStateHandleException extends IllegalStateException {

Review comment:
       I guess the benefit of using an additional exception to avoid code duplication. I'm a bit torn if a small service method would not achieve the same but I guess it's okay like this.

##########
File path: flink-runtime/src/main/java/org/apache/flink/runtime/state/UnexpectedStateHandleException.java
##########
@@ -0,0 +1,46 @@
+/*
+ * 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.runtime.state;
+
+import org.apache.flink.shaded.guava18.com.google.common.base.Joiner;
+
+/**
+ * Signals that an operation did not get the type of {@link StateObject} that was expected. This can
+ * mostly happen when a different {@link StateBackend} from the one that was used for taking a
+ * checkpoint/savepoint is used when restoring.
+ */
+public class UnexpectedStateHandleException extends IllegalStateException {
+
+	@SuppressWarnings("unchecked")
+	public UnexpectedStateHandleException(
+			Class<? extends StateObject> expectedStateHandleClass,
+			Class<? extends StateObject> actualStateHandleClass) {
+		this(new Class[] {expectedStateHandleClass}, actualStateHandleClass);
+	}
+
+	public UnexpectedStateHandleException(
+			Class<? extends StateObject>[] expectedStateHandleClasses,
+			Class<? extends StateObject> actualStateHandleClass) {

Review comment:
       Swap arguments and use ellipse to avoid 2 ctors?

##########
File path: flink-runtime/src/test/java/org/apache/flink/runtime/state/UnexpectedStateHandleExceptionTest.java
##########
@@ -0,0 +1,55 @@
+/*
+ * 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.runtime.state;
+
+import org.junit.Test;
+
+import static org.hamcrest.CoreMatchers.containsString;
+import static org.junit.Assert.assertThat;
+
+/**
+ * Tests for {@link UnexpectedStateHandleException}.
+ */
+public class UnexpectedStateHandleExceptionTest {

Review comment:
       Rather then these no-op tests, I'd rather see an ITCase where we actually save with rocksdb and read with file state backend.




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