YARN-9092. Create an object for cgroups mount enable and cgroups mount path as they belong together. Contributed by Gergely Pollak

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/containermanager/linux/resources/CGroupsHandlerImpl.java

@@ -66,8 +66,7 @@ class CGroupsHandlerImpl implements CGroupsHandler {
 
   private final String mtabFile;
   private final String cGroupPrefix;
-  private final boolean enableCGroupMount;
+  private final CGroupsMountConfig cGroupsMountConfig;
-  private final String cGroupMountPath;
   private final long deleteCGroupTimeout;
   private final long deleteCGroupDelay;
   private Map<CGroupController, String> controllerPaths;
@@ -91,10 +90,7 @@ class CGroupsHandlerImpl implements CGroupsHandler {
     this.cGroupPrefix = conf.get(YarnConfiguration.
         NM_LINUX_CONTAINER_CGROUPS_HIERARCHY, "/hadoop-yarn")
         .replaceAll("^/+", "").replaceAll("/+$", "");
-    this.enableCGroupMount = conf.getBoolean(YarnConfiguration.
+    this.cGroupsMountConfig = new CGroupsMountConfig(conf);
-        NM_LINUX_CONTAINER_CGROUPS_MOUNT, false);
-    this.cGroupMountPath = conf.get(YarnConfiguration.
-        NM_LINUX_CONTAINER_CGROUPS_MOUNT_PATH, null);
     this.deleteCGroupTimeout = conf.getLong(
         YarnConfiguration.NM_LINUX_CONTAINER_CGROUPS_DELETE_TIMEOUT,
         YarnConfiguration.DEFAULT_NM_LINUX_CONTAINER_CGROUPS_DELETE_TIMEOUT) +
@@ -150,9 +146,9 @@ private void initializeControllerPaths() throws ResourceHandlerException {
     Map<String, Set<String>> newMtab = null;
     Map<CGroupController, String> cPaths;
     try {
-      if (this.cGroupMountPath != null && !this.enableCGroupMount) {
+      if (this.cGroupsMountConfig.mountDisabledButMountPathDefined()) {
         newMtab = ResourceHandlerModule.
-            parseConfiguredCGroupPath(this.cGroupMountPath);
+            parseConfiguredCGroupPath(this.cGroupsMountConfig.getMountPath());
       }
 
       if (newMtab == null) {
@@ -282,14 +278,10 @@ static String findControllerInMtab(String controller,
 
   private void mountCGroupController(CGroupController controller)
       throws ResourceHandlerException {
-    if (cGroupMountPath == null) {
-      throw new ResourceHandlerException(
-          String.format("Cgroups mount path not specified in %s.",
-              YarnConfiguration.NM_LINUX_CONTAINER_CGROUPS_MOUNT_PATH));
-    }
     String existingMountPath = getControllerPath(controller);
     String requestedMountPath =
-        new File(cGroupMountPath, controller.getName()).getAbsolutePath();
+        new File(cGroupsMountConfig.getMountPath(),
+            controller.getName()).getAbsolutePath();
 
     if (existingMountPath == null ||
         !requestedMountPath.equals(existingMountPath)) {
@@ -367,7 +359,8 @@ public String getPathForCGroupParam(CGroupController controller,
   @Override
   public void initializeCGroupController(CGroupController controller) throws
       ResourceHandlerException {
-    if (enableCGroupMount) {
+    if (this.cGroupsMountConfig.isMountEnabled() &&
+        cGroupsMountConfig.ensureMountPathIsDefined()) {
       // We have a controller that needs to be mounted
       mountCGroupController(controller);
     }
@@ -611,7 +604,7 @@ public String getCGroupParam(CGroupController controller, String cGroupId,
 
   @Override
   public String getCGroupMountPath() {
-    return cGroupMountPath;
+    return this.cGroupsMountConfig.getMountPath();
   }
 
   @Override
@@ -619,8 +612,7 @@ public String toString() {
     return CGroupsHandlerImpl.class.getName() + "{" +
         "mtabFile='" + mtabFile + '\'' +
         ", cGroupPrefix='" + cGroupPrefix + '\'' +
-        ", enableCGroupMount=" + enableCGroupMount +
+        ", cGroupsMountConfig=" + cGroupsMountConfig +
-        ", cGroupMountPath='" + cGroupMountPath + '\'' +
         ", deleteCGroupTimeout=" + deleteCGroupTimeout +
         ", deleteCGroupDelay=" + deleteCGroupDelay +
         '}';

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/containermanager/linux/resources/CGroupsMountConfig.java

@@ -0,0 +1,72 @@
+/*
+ * 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.yarn.server.nodemanager.containermanager.linux.resources;
+
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.yarn.conf.YarnConfiguration;
+
+/**
+ * Stores config related to cgroups.
+ */
+public class CGroupsMountConfig {
+  private final boolean enableMount;
+  private final String mountPath;
+
+  public CGroupsMountConfig(Configuration conf) {
+    this.enableMount = conf.getBoolean(YarnConfiguration.
+        NM_LINUX_CONTAINER_CGROUPS_MOUNT, false);
+    this.mountPath = conf.get(YarnConfiguration.
+        NM_LINUX_CONTAINER_CGROUPS_MOUNT_PATH, null);
+  }
+
+  public boolean ensureMountPathIsDefined() throws ResourceHandlerException {
+    if (mountPath == null) {
+      throw new ResourceHandlerException(
+          String.format("Cgroups mount path not specified in %s.",
+              YarnConfiguration.NM_LINUX_CONTAINER_CGROUPS_MOUNT_PATH));
+    }
+    return true;
+  }
+
+  public boolean isMountPathDefined() {
+    return mountPath != null;
+  }
+
+  public boolean isMountEnabled() {
+    return enableMount;
+  }
+
+  public boolean mountDisabledButMountPathDefined() {
+    return !enableMount && mountPath != null;
+  }
+
+  public boolean mountEnabledAndMountPathDefined() {
+    return enableMount && mountPath != null;
+  }
+
+  public String getMountPath() {
+    return mountPath;
+  }
+
+  @Override
+  public String toString() {
+    return "CGroupsMountConfig{" +
+        "enableMount=" + enableMount +
+        ", mountPath='" + mountPath + '\'' +
+        '}';
+  }
+}

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/util/CgroupsLCEResourcesHandler.java

@@ -37,6 +37,8 @@
 import java.util.Set;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
+
+import org.apache.hadoop.yarn.server.nodemanager.containermanager.linux.resources.CGroupsMountConfig;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -73,8 +75,7 @@ public class CgroupsLCEResourcesHandler implements LCEResourcesHandler {
 
   private Configuration conf;
   private String cgroupPrefix;
-  private boolean cgroupMount;
+  private CGroupsMountConfig cGroupsMountConfig;
-  private String cgroupMountPath;
 
   private boolean cpuWeightEnabled = true;
   private boolean strictResourceUsageMode = false;
@@ -115,11 +116,7 @@ void initConfig() throws IOException {
 
     this.cgroupPrefix = conf.get(YarnConfiguration.
             NM_LINUX_CONTAINER_CGROUPS_HIERARCHY, "/hadoop-yarn");
-    this.cgroupMount = conf.getBoolean(YarnConfiguration.
+    this.cGroupsMountConfig = new CGroupsMountConfig(conf);
-            NM_LINUX_CONTAINER_CGROUPS_MOUNT, false);
-    this.cgroupMountPath = conf.get(YarnConfiguration.
-            NM_LINUX_CONTAINER_CGROUPS_MOUNT_PATH, null);
-
     this.deleteCgroupTimeout = conf.getLong(
         YarnConfiguration.NM_LINUX_CONTAINER_CGROUPS_DELETE_TIMEOUT,
         YarnConfiguration.DEFAULT_NM_LINUX_CONTAINER_CGROUPS_DELETE_TIMEOUT);
@@ -156,10 +153,10 @@ void init(LinuxContainerExecutor lce, ResourceCalculatorPlugin plugin)
     initConfig();
 
     // mount cgroups if requested
-    if (cgroupMount && cgroupMountPath != null) {
+    if (cGroupsMountConfig.mountEnabledAndMountPathDefined()) {
       ArrayList<String> cgroupKVs = new ArrayList<String>();
-      cgroupKVs.add(CONTROLLER_CPU + "=" + cgroupMountPath + "/" +
+      cgroupKVs.add(CONTROLLER_CPU + "=" +
-                    CONTROLLER_CPU);
+          cGroupsMountConfig.getMountPath() + "/" + CONTROLLER_CPU);
       lce.mountCgroups(cgroupKVs, cgroupPrefix);
     }
 
@@ -456,9 +453,9 @@ private void initializeControllerPaths() throws IOException {
     String controllerPath;
     Map<String, Set<String>> parsedMtab = null;
 
-    if (this.cgroupMountPath != null && !this.cgroupMount) {
+    if (this.cGroupsMountConfig.mountDisabledButMountPathDefined()) {
       parsedMtab = ResourceHandlerModule.
-          parseConfiguredCGroupPath(this.cgroupMountPath);
+          parseConfiguredCGroupPath(this.cGroupsMountConfig.getMountPath());
     }
 
     if (parsedMtab == null) {