YARN-5596. Fix failing unit test in TestDockerContainerRuntime. Contributed by Sidharta Seethana.

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

@@ -146,6 +146,8 @@ public class DockerLinuxContainerRuntime implements LinuxContainerRuntime {
   public static final String ENV_DOCKER_CONTAINER_LOCAL_RESOURCE_MOUNTS =
       "YARN_CONTAINER_RUNTIME_DOCKER_LOCAL_RESOURCE_MOUNTS";
 
+  static final String CGROUPS_ROOT_DIRECTORY = "/sys/fs/cgroup";
+
   private Configuration conf;
   private DockerClient dockerClient;
   private PrivilegedOperationExecutor privilegedOperationExecutor;
@@ -437,7 +439,6 @@ public class DockerLinuxContainerRuntime implements LinuxContainerRuntime {
         LOCALIZED_RESOURCES);
     @SuppressWarnings("unchecked")
     List<String> userLocalDirs = ctx.getExecutionAttribute(USER_LOCAL_DIRS);
-
     Set<String> capabilities = new HashSet<>(Arrays.asList(conf.getStrings(
         YarnConfiguration.NM_DOCKER_CONTAINER_CAPABILITIES,
         YarnConfiguration.DEFAULT_NM_DOCKER_CONTAINER_CAPABILITIES)));
@@ -449,7 +450,8 @@ public class DockerLinuxContainerRuntime implements LinuxContainerRuntime {
         .setContainerWorkDir(containerWorkDir.toString())
         .setNetworkType(network)
         .setCapabilities(capabilities)
-        .addMountLocation("/sys/fs/cgroup", "/sys/fs/cgroup:ro", false);
+        .addMountLocation(CGROUPS_ROOT_DIRECTORY,
+            CGROUPS_ROOT_DIRECTORY + ":ro", false);
     List<String> allDirs = new ArrayList<>(containerLocalDirs);
 
     allDirs.addAll(filecacheDirs);

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

@@ -257,6 +257,18 @@ public class TestDockerContainerRuntime {
     return expectedCapabilitiesString.toString();
   }
 
+  private String getExpectedCGroupsMountString() {
+    boolean cGroupsMountExists = new File(
+        DockerLinuxContainerRuntime.CGROUPS_ROOT_DIRECTORY).exists();
+
+    if(cGroupsMountExists) {
+      return "-v " + DockerLinuxContainerRuntime.CGROUPS_ROOT_DIRECTORY
+          + ":" + DockerLinuxContainerRuntime.CGROUPS_ROOT_DIRECTORY + ":ro ";
+    } else {
+      return "";
+    }
+  }
+
   @Test
   public void testDockerContainerLaunch()
       throws ContainerExecutionException, PrivilegedOperationException,
@@ -276,7 +288,7 @@ public class TestDockerContainerRuntime {
         .append("--workdir=%3$s ")
         .append("--net=host ")
         .append(getExpectedTestCapabilitiesArgumentString())
-        .append("-v /sys/fs/cgroup:/sys/fs/cgroup:ro ")
+        .append(getExpectedCGroupsMountString())
         .append("-v %4$s:%4$s ")
         .append("-v %5$s:%5$s ")
         .append("-v %6$s:%6$s ")
@@ -382,7 +394,7 @@ public class TestDockerContainerRuntime {
             .append("--workdir=%3$s ")
             .append("--net=" + allowedNetwork + " ")
             .append(getExpectedTestCapabilitiesArgumentString())
-            .append("-v /sys/fs/cgroup:/sys/fs/cgroup:ro ")
+            .append(getExpectedCGroupsMountString())
             .append("-v %4$s:%4$s ").append("-v %5$s:%5$s ")
             .append("-v %6$s:%6$s ").append("-v %7$s:%7$s ")
             .append("-v %8$s:%8$s ").append("%9$s ")
@@ -437,7 +449,7 @@ public class TestDockerContainerRuntime {
             .append("--workdir=%3$s ")
             .append("--net=" + customNetwork1 + " ")
             .append(getExpectedTestCapabilitiesArgumentString())
-            .append("-v /sys/fs/cgroup:/sys/fs/cgroup:ro ")
+            .append(getExpectedCGroupsMountString())
             .append("-v %4$s:%4$s ").append("-v %5$s:%5$s ")
             .append("-v %6$s:%6$s ").append("-v %7$s:%7$s ")
             .append("-v %8$s:%8$s ").append("%9$s ")
@@ -474,7 +486,7 @@ public class TestDockerContainerRuntime {
             .append("--workdir=%3$s ")
             .append("--net=" + customNetwork2 + " ")
             .append(getExpectedTestCapabilitiesArgumentString())
-            .append("-v /sys/fs/cgroup:/sys/fs/cgroup:ro ")
+            .append(getExpectedCGroupsMountString())
             .append("-v %4$s:%4$s ").append("-v %5$s:%5$s ")
             .append("-v %6$s:%6$s ").append("-v %7$s:%7$s ")
             .append("-v %8$s:%8$s ").append("%9$s ")