[GitHub] [hive] kgyrtkirk commented on a change in pull request #1428: HIVE-24068: Add re-execution plugin for handling DAG submission failures

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kgyrtkirk commented on a change in pull request #1428:
URL: https://github.com/apache/hive/pull/1428#discussion_r476242856



##########
File path: ql/src/java/org/apache/hadoop/hive/ql/reexec/ReExecutionDagSubmitPlugin.java
##########
@@ -0,0 +1,86 @@
+/*
+ * 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.hadoop.hive.ql.reexec;
+
+import org.apache.hadoop.hive.ql.Driver;
+import org.apache.hadoop.hive.ql.hooks.ExecuteWithHookContext;
+import org.apache.hadoop.hive.ql.hooks.HookContext;
+import org.apache.hadoop.hive.ql.hooks.HookContext.HookType;
+import org.apache.hadoop.hive.ql.plan.mapper.PlanMapper;
+import org.apache.hadoop.hive.ql.processors.CommandProcessorException;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * Re-Executes a query when DAG submission fails after get session returned successfully.
+ */
+public class ReExecutionDagSubmitPlugin implements IReExecutionPlugin {
+
+  private static final Logger LOG = LoggerFactory.getLogger(ReExecutionDagSubmitPlugin.class);
+  class LocalHook implements ExecuteWithHookContext {
+
+    @Override
+    public void run(HookContext hookContext) throws Exception {
+      if (hookContext.getHookType() == HookType.ON_FAILURE_HOOK) {
+        Throwable exception = hookContext.getException();
+        if (exception != null) {
+          if (exception.getMessage() != null) {
+            // there could be race condition where getSession could return a healthy AM but by the time DAG is submitted
+            // the AM could become unhealthy/unreachable (possible DNS or network issues) which can fail tez DAG
+            // submission. Since the DAG hasn't started execution yet this failure can be safely restarted.

Review comment:
       I think this explanation could be moved into the class documentation




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