YARN-8667. Cleanup symlinks when container restarted by NM.

Contributed by Chandni Singh

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

@@ -27,6 +27,7 @@
 import java.nio.charset.Charset;
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.HashMap;
 import java.util.List;
 import java.util.LinkedHashSet;
 import java.util.Map;
@@ -35,6 +36,7 @@
 import java.util.concurrent.locks.ReentrantReadWriteLock;
 import java.util.concurrent.locks.ReentrantReadWriteLock.ReadLock;
 import java.util.concurrent.locks.ReentrantReadWriteLock.WriteLock;
+
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -417,20 +419,9 @@ public void writeLaunchEnv(OutputStream out, Map<String, String> environment,
 
     if (resources != null) {
       sb.echo("Setting up job resources");
-      for (Map.Entry<Path, List<String>> resourceEntry :
-          resources.entrySet()) {
-        for (String linkName : resourceEntry.getValue()) {
-          if (new Path(linkName).getName().equals(WILDCARD)) {
-            // If this is a wildcarded path, link to everything in the
-            // directory from the working directory
-            for (File wildLink : readDirAsUser(user, resourceEntry.getKey())) {
-              sb.symlink(new Path(wildLink.toString()),
-                  new Path(wildLink.getName()));
-            }
-          } else {
-            sb.symlink(resourceEntry.getKey(), new Path(linkName));
-          }
-        }
+      Map<Path, Path> symLinks = resolveSymLinks(resources, user);
+      for (Map.Entry<Path, Path> symLink : symLinks.entrySet()) {
+        sb.symlink(symLink.getKey(), symLink.getValue());
       }
     }
 
@@ -791,6 +782,28 @@ public void resumeContainer(Container container) {
     throw new UnsupportedOperationException();
   }
 
+  /**
+   * Perform any cleanup before the next launch of the container.
+   * @param container         container
+   */
+  public void cleanupBeforeRelaunch(Container container)
+      throws IOException, InterruptedException {
+    if (container.getLocalizedResources() != null) {
+
+      Map<Path, Path> symLinks = resolveSymLinks(
+          container.getLocalizedResources(), container.getUser());
+
+      for (Map.Entry<Path, Path> symLink : symLinks.entrySet()) {
+        LOG.debug("{} deleting {}", container.getContainerId(),
+            symLink.getValue());
+        deleteAsUser(new DeletionAsUserContext.Builder()
+            .setUser(container.getUser())
+            .setSubDir(symLink.getValue())
+            .build());
+      }
+    }
+  }
+
   /**
    * Get the process-identifier for the container.
    *
@@ -870,4 +883,25 @@ public void run() {
       }
     }
   }
+
+  private Map<Path, Path> resolveSymLinks(Map<Path,
+      List<String>> resources, String user) {
+    Map<Path, Path> symLinks = new HashMap<>();
+    for (Map.Entry<Path, List<String>> resourceEntry :
+        resources.entrySet()) {
+      for (String linkName : resourceEntry.getValue()) {
+        if (new Path(linkName).getName().equals(WILDCARD)) {
+          // If this is a wildcarded path, link to everything in the
+          // directory from the working directory
+          for (File wildLink : readDirAsUser(user, resourceEntry.getKey())) {
+            symLinks.put(new Path(wildLink.toString()),
+                new Path(wildLink.getName()));
+          }
+        } else {
+          symLinks.put(resourceEntry.getKey(), new Path(linkName));
+        }
+      }
+    }
+    return symLinks;
+  }
 }

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

@@ -1868,6 +1868,13 @@ protected void cleanupContainerFiles(Path containerWorkDir) {
     deleteAsUser(new Path(containerWorkDir, CONTAINER_SCRIPT));
     // delete TokensPath
     deleteAsUser(new Path(containerWorkDir, FINAL_CONTAINER_TOKENS_FILE));
+
+    // delete symlinks because launch script will create symlinks again
+    try {
+      exec.cleanupBeforeRelaunch(container);
+    } catch (IOException | InterruptedException e) {
+      LOG.warn("{} exec failed to cleanup", container.getContainerId(), e);
+    }
   }
 
   private void deleteAsUser(Path path) {

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/test/java/org/apache/hadoop/yarn/server/nodemanager/TestContainerExecutor.java

@@ -18,9 +18,17 @@
 
 package org.apache.hadoop.yarn.server.nodemanager;
 
+import java.nio.file.Files;
+import java.nio.file.Paths;
 import java.util.Arrays;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
 
+import com.google.common.collect.Lists;
+import org.apache.commons.io.FileUtils;
 import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.fs.Path;
 import org.apache.hadoop.util.Shell;
 import org.apache.hadoop.yarn.api.records.Resource;
 import org.apache.hadoop.yarn.conf.YarnConfiguration;
@@ -28,13 +36,13 @@
 import org.apache.hadoop.yarn.server.nodemanager.containermanager.container.Container;
 import org.apache.hadoop.yarn.server.nodemanager.executor.ContainerReapContext;
 import org.apache.hadoop.yarn.server.nodemanager.util.NodeManagerHardwareUtils;
-import org.apache.hadoop.yarn.util.ResourceCalculatorPlugin;
 import org.junit.Assert;
 import org.junit.Test;
 
 import static org.apache.hadoop.test.PlatformAssumptions.assumeWindows;
 import static org.junit.Assert.*;
 import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
 
 @SuppressWarnings("deprecation")
 public class TestContainerExecutor {
@@ -168,4 +176,25 @@ public void testReapContainer() throws Exception {
     builder.setContainer(container).setUser("foo");
     assertTrue(containerExecutor.reapContainer(builder.build()));
   }
+
+  @Test
+  public void testCleanupBeforeLaunch() throws Exception {
+    Container container = mock(Container.class);
+    java.nio.file.Path linkName = Paths.get("target/linkName");
+    java.nio.file.Path target = Paths.get("target");
+    //deletes the link if it already exists because of previous test failures
+    FileUtils.deleteQuietly(linkName.toFile());
+    Files.createSymbolicLink(linkName.toAbsolutePath(),
+        target.toAbsolutePath());
+
+    Map<Path, List<String>> localResources = new HashMap<>();
+    localResources.put(new Path(target.toFile().getAbsolutePath()),
+        Lists.newArrayList(linkName.toFile().getAbsolutePath()));
+
+    when(container.getLocalizedResources())
+        .thenReturn(localResources);
+    when(container.getUser()).thenReturn(System.getProperty("user.name"));
+    containerExecutor.cleanupBeforeRelaunch(container);
+    Assert.assertTrue(!Files.exists(linkName));
+  }
 }