YARN-8228. Added hostname length check for docker container.

            Contributed by Shane Kumpf

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/containermanager/linux/runtime/DockerLinuxContainerRuntime.java

@@ -199,6 +199,7 @@ public class DockerLinuxContainerRuntime implements LinuxContainerRuntime {
       HOSTNAME_PATTERN);
   private static final Pattern USER_MOUNT_PATTERN = Pattern.compile(
       "(?<=^|,)([^:\\x00]+):([^:\\x00]+):([a-z]+)");
+  private static final int HOST_NAME_LENGTH = 64;
 
   @InterfaceAudience.Private
   public static final String ENV_DOCKER_CONTAINER_IMAGE =
@@ -541,6 +542,11 @@ public class DockerLinuxContainerRuntime implements LinuxContainerRuntime {
         throw new ContainerExecutionException("Hostname '" + hostname
             + "' doesn't match docker hostname pattern");
       }
+      if (hostname.length() > HOST_NAME_LENGTH) {
+        throw new ContainerExecutionException(
+            "Hostname can not be greater than " + HOST_NAME_LENGTH
+                + " characters: " + hostname);
+      }
     }
   }
 

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/test/java/org/apache/hadoop/yarn/server/nodemanager/containermanager/linux/runtime/TestDockerContainerRuntime.java

@@ -1539,6 +1539,19 @@ public class TestDockerContainerRuntime {
     }
   }
 
+  @Test
+  public void testValidDockerHostnameLength() throws Exception {
+    String validLength = "example.test.site";
+    DockerLinuxContainerRuntime.validateHostname(validLength);
+  }
+
+  @Test(expected = ContainerExecutionException.class)
+  public void testInvalidDockerHostnameLength() throws Exception {
+    String invalidLength =
+        "exampleexampleexampleexampleexampleexampleexampleexample.test.site";
+    DockerLinuxContainerRuntime.validateHostname(invalidLength);
+  }
+
   @SuppressWarnings("unchecked")
   private void checkVolumeCreateCommand()
       throws PrivilegedOperationException, IOException {