YARN-6999. Add log about how to solve Error: Could not find or load main class org.apache.hadoop.mapreduce.v2.app.MRAppMaster. (Linlin Zhou via gtcarrera9)

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/containermanager/launcher/ContainerLaunch.java

@@ -564,9 +564,11 @@ public class ContainerLaunch implements Callable<Integer> {
         errorFileIS = fileSystem.open(errorFile);
         errorFileIS.readFully(startPosition, tailBuffer);
 
+        String tailBufferMsg = new String(tailBuffer, StandardCharsets.UTF_8);
         diagnosticInfo.append("Last ").append(tailSizeInBytes)
             .append(" bytes of ").append(errorFile.getName()).append(" :\n")
-            .append(new String(tailBuffer, StandardCharsets.UTF_8));
+            .append(tailBufferMsg).append("\n")
+            .append(analysesErrorMsgOfContainerExitWithFailure(tailBufferMsg));
       }
     } catch (IOException e) {
       LOG.error("Failed to get tail of the container's error log file", e);
@@ -580,6 +582,29 @@ public class ContainerLaunch implements Callable<Integer> {
             diagnosticInfo.toString()));
   }
 
+  private String analysesErrorMsgOfContainerExitWithFailure(String errorMsg) {
+    StringBuilder analysis = new StringBuilder();
+    if (errorMsg.indexOf("Error: Could not find or load main class"
+        + " org.apache.hadoop.mapreduce") != -1) {
+      analysis.append("Please check whether your etc/hadoop/mapred-site.xml "
+          + "contains the below configuration:\n");
+      analysis.append("<property>\n")
+          .append("  <name>yarn.app.mapreduce.am.env</name>\n")
+          .append("  <value>HADOOP_MAPRED_HOME=${full path of your hadoop "
+              + "distribution directory}</value>\n")
+          .append("</property>\n<property>\n")
+          .append("  <name>mapreduce.map.env</name>\n")
+          .append("  <value>HADOOP_MAPRED_HOME=${full path of your hadoop "
+              + "distribution directory}</value>\n")
+          .append("</property>\n<property>\n")
+          .append("  <name>mapreduce.reduce.e nv</name>\n")
+          .append("  <value>HADOOP_MAPRED_HOME=${full path of your hadoop "
+              + "distribution directory}</value>\n")
+          .append("</property>\n");
+    }
+    return analysis.toString();
+  }
+
   protected String getPidFileSubpath(String appIdStr, String containerIdStr) {
     return getContainerPrivateDir(appIdStr, containerIdStr) + Path.SEPARATOR
         + String.format(ContainerLaunch.PID_FILE_NAME_FMT, containerIdStr);