[SPARK-4236] Cleanup removed applications' files in shuffle service

This relies on a hook from whoever is hosting the shuffle service to invoke removeApplication() when the application is completed. Once invoked, we will clean up all the executors' shuffle directories we know about.

Author: Aaron Davidson <aaron@databricks.com>

Closes #3126 from aarondav/cleanup and squashes the following commits:

33a64a9 [Aaron Davidson] Missing brace
e6e428f [Aaron Davidson] Address comments
16a0d27 [Aaron Davidson] Cleanup
e4df3e7 [Aaron Davidson] [SPARK-4236] Cleanup removed applications' files in shuffle service

core/src/main/scala/org/apache/spark/util/Utils.scala

@@ -755,6 +755,7 @@ private[spark] object Utils extends Logging {
   /**
    * Delete a file or directory and its contents recursively.
    * Don't follow directories if they are symlinks.
+   * Throws an exception if deletion is unsuccessful.
    */
   def deleteRecursively(file: File) {
     if (file != null) {

core/src/test/scala/org/apache/spark/ExternalShuffleServiceSuite.scala

@@ -63,8 +63,9 @@ class ExternalShuffleServiceSuite extends ShuffleSuite with BeforeAndAfterAll {
     rdd.count()
     rdd.count()
 
-    // Invalidate the registered executors, disallowing access to their shuffle blocks.
-    rpcHandler.clearRegisteredExecutors()
+    // Invalidate the registered executors, disallowing access to their shuffle blocks (without
+    // deleting the actual shuffle files, so we could access them without the shuffle service).
+    rpcHandler.applicationRemoved(sc.conf.getAppId, false /* cleanupLocalDirs */)
 
     // Now Spark will receive FetchFailed, and not retry the stage due to "spark.test.noStageRetry"
     // being set.

network/common/src/main/java/org/apache/spark/network/util/JavaUtils.java

@@ -22,16 +22,22 @@
 import java.io.ByteArrayInputStream;
 import java.io.ByteArrayOutputStream;
 import java.io.Closeable;
+import java.io.File;
 import java.io.IOException;
 import java.io.ObjectInputStream;
 import java.io.ObjectOutputStream;
 
+import com.google.common.base.Preconditions;
 import com.google.common.io.Closeables;
 import com.google.common.base.Charsets;
 import io.netty.buffer.Unpooled;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+/**
+ * General utilities available in the network package. Many of these are sourced from Spark's
+ * own Utils, just accessible within this package.
+ */
 public class JavaUtils {
   private static final Logger logger = LoggerFactory.getLogger(JavaUtils.class);
 
@@ -93,4 +99,57 @@ public static ByteBuffer stringToBytes(String s) {
   public static String bytesToString(ByteBuffer b) {
     return Unpooled.wrappedBuffer(b).toString(Charsets.UTF_8);
   }
+
+  /*
+   * Delete a file or directory and its contents recursively.
+   * Don't follow directories if they are symlinks.
+   * Throws an exception if deletion is unsuccessful.
+   */
+  public static void deleteRecursively(File file) throws IOException {
+    if (file == null) { return; }
+
+    if (file.isDirectory() && !isSymlink(file)) {
+      IOException savedIOException = null;
+      for (File child : listFilesSafely(file)) {
+        try {
+          deleteRecursively(child);
+        } catch (IOException e) {
+          // In case of multiple exceptions, only last one will be thrown
+          savedIOException = e;
+        }
+      }
+      if (savedIOException != null) {
+        throw savedIOException;
+      }
+    }
+
+    boolean deleted = file.delete();
+    // Delete can also fail if the file simply did not exist.
+    if (!deleted && file.exists()) {
+      throw new IOException("Failed to delete: " + file.getAbsolutePath());
+    }
+  }
+
+  private static File[] listFilesSafely(File file) throws IOException {
+    if (file.exists()) {
+      File[] files = file.listFiles();
+      if (files == null) {
+        throw new IOException("Failed to list files for dir: " + file);
+      }
+      return files;
+    } else {
+      return new File[0];
+    }
+  }
+
+  private static boolean isSymlink(File file) throws IOException {
+    Preconditions.checkNotNull(file);
+    File fileInCanonicalDir = null;
+    if (file.getParent() == null) {
+      fileInCanonicalDir = file;
+    } else {
+      fileInCanonicalDir = new File(file.getParentFile().getCanonicalFile(), file.getName());
+    }
+    return !fileInCanonicalDir.getCanonicalFile().equals(fileInCanonicalDir.getAbsoluteFile());
+  }
 }

network/shuffle/src/main/java/org/apache/spark/network/shuffle/ExternalShuffleBlockHandler.java

@@ -94,9 +94,11 @@ public StreamManager getStreamManager() {
     return streamManager;
   }
 
-  /** For testing, clears all executors registered with "RegisterExecutor". */
-  @VisibleForTesting
-  public void clearRegisteredExecutors() {
-    blockManager.clearRegisteredExecutors();
+  /**
+   * Removes an application (once it has been terminated), and optionally will clean up any
+   * local directories associated with the executors of that application in a separate thread.
+   */
+  public void applicationRemoved(String appId, boolean cleanupLocalDirs) {
+    blockManager.applicationRemoved(appId, cleanupLocalDirs);
   }
 }

network/shuffle/src/main/java/org/apache/spark/network/shuffle/ExternalShuffleBlockManager.java

@@ -21,9 +21,15 @@
 import java.io.File;
 import java.io.FileInputStream;
 import java.io.IOException;
-import java.util.concurrent.ConcurrentHashMap;
+import java.util.Iterator;
+import java.util.Map;
+import java.util.concurrent.ConcurrentMap;
+import java.util.concurrent.Executor;
+import java.util.concurrent.Executors;
 
 import com.google.common.annotations.VisibleForTesting;
+import com.google.common.base.Objects;
+import com.google.common.collect.Maps;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -43,21 +49,30 @@
 public class ExternalShuffleBlockManager {
   private final Logger logger = LoggerFactory.getLogger(ExternalShuffleBlockManager.class);
 
-  // Map from "appId-execId" to the executor's configuration.
-  private final ConcurrentHashMap<String, ExecutorShuffleInfo> executors =
-    new ConcurrentHashMap<String, ExecutorShuffleInfo>();
+  // Map containing all registered executors' metadata.
+  private final ConcurrentMap<AppExecId, ExecutorShuffleInfo> executors;
 
-  // Returns an id suitable for a single executor within a single application.
-  private String getAppExecId(String appId, String execId) {
-    return appId + "-" + execId;
+  // Single-threaded Java executor used to perform expensive recursive directory deletion.
+  private final Executor directoryCleaner;
+
+  public ExternalShuffleBlockManager() {
+    // TODO: Give this thread a name.
+    this(Executors.newSingleThreadExecutor());
+  }
+
+  // Allows tests to have more control over when directories are cleaned up.
+  @VisibleForTesting
+  ExternalShuffleBlockManager(Executor directoryCleaner) {
+    this.executors = Maps.newConcurrentMap();
+    this.directoryCleaner = directoryCleaner;
   }
 
   /** Registers a new Executor with all the configuration we need to find its shuffle files. */
   public void registerExecutor(
       String appId,
       String execId,
       ExecutorShuffleInfo executorInfo) {
-    String fullId = getAppExecId(appId, execId);
+    AppExecId fullId = new AppExecId(appId, execId);
     logger.info("Registered executor {} with {}", fullId, executorInfo);
     executors.put(fullId, executorInfo);
   }
@@ -78,7 +93,7 @@ public ManagedBuffer getBlockData(String appId, String execId, String blockId) {
     int mapId = Integer.parseInt(blockIdParts[2]);
     int reduceId = Integer.parseInt(blockIdParts[3]);
 
-    ExecutorShuffleInfo executor = executors.get(getAppExecId(appId, execId));
+    ExecutorShuffleInfo executor = executors.get(new AppExecId(appId, execId));
     if (executor == null) {
       throw new RuntimeException(
         String.format("Executor is not registered (appId=%s, execId=%s)", appId, execId));
@@ -94,6 +109,56 @@ public ManagedBuffer getBlockData(String appId, String execId, String blockId) {
     }
   }
 
+  /**
+   * Removes our metadata of all executors registered for the given application, and optionally
+   * also deletes the local directories associated with the executors of that application in a
+   * separate thread.
+   *
+   * It is not valid to call registerExecutor() for an executor with this appId after invoking
+   * this method.
+   */
+  public void applicationRemoved(String appId, boolean cleanupLocalDirs) {
+    logger.info("Application {} removed, cleanupLocalDirs = {}", appId, cleanupLocalDirs);
+    Iterator<Map.Entry<AppExecId, ExecutorShuffleInfo>> it = executors.entrySet().iterator();
+    while (it.hasNext()) {
+      Map.Entry<AppExecId, ExecutorShuffleInfo> entry = it.next();
+      AppExecId fullId = entry.getKey();
+      final ExecutorShuffleInfo executor = entry.getValue();
+
+      // Only touch executors associated with the appId that was removed.
+      if (appId.equals(fullId.appId)) {
+        it.remove();
+
+        if (cleanupLocalDirs) {
+          logger.info("Cleaning up executor {}'s {} local dirs", fullId, executor.localDirs.length);
+
+          // Execute the actual deletion in a different thread, as it may take some time.
+          directoryCleaner.execute(new Runnable() {
+            @Override
+            public void run() {
+              deleteExecutorDirs(executor.localDirs);
+            }
+          });
+        }
+      }
+    }
+  }
+
+  /**
+   * Synchronously deletes each directory one at a time.
+   * Should be executed in its own thread, as this may take a long time.
+   */
+  private void deleteExecutorDirs(String[] dirs) {
+    for (String localDir : dirs) {
+      try {
+        JavaUtils.deleteRecursively(new File(localDir));
+        logger.debug("Successfully cleaned up directory: " + localDir);
+      } catch (Exception e) {
+        logger.error("Failed to delete directory: " + localDir, e);
+      }
+    }
+  }
+
   /**
    * Hash-based shuffle data is simply stored as one file per block.
    * This logic is from FileShuffleBlockManager.
@@ -146,9 +211,36 @@ static File getFile(String[] localDirs, int subDirsPerLocalDir, String filename)
     return new File(new File(localDir, String.format("%02x", subDirId)), filename);
   }
 
-  /** For testing, clears all registered executors. */
-  @VisibleForTesting
-  void clearRegisteredExecutors() {
-    executors.clear();
+  /** Simply encodes an executor's full ID, which is appId + execId. */
+  private static class AppExecId {
+    final String appId;
+    final String execId;
+
+    private AppExecId(String appId, String execId) {
+      this.appId = appId;
+      this.execId = execId;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+      if (this == o) return true;
+      if (o == null || getClass() != o.getClass()) return false;
+
+      AppExecId appExecId = (AppExecId) o;
+      return Objects.equal(appId, appExecId.appId) && Objects.equal(execId, appExecId.execId);
+    }
+
+    @Override
+    public int hashCode() {
+      return Objects.hashCode(appId, execId);
+    }
+
+    @Override
+    public String toString() {
+      return Objects.toStringHelper(this)
+        .add("appId", appId)
+        .add("execId", execId)
+        .toString();
+    }
   }
 }