| /** |
| * 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.io.nativeio; |
| |
| import java.io.FileInputStream; |
| import java.io.IOException; |
| import java.io.FileDescriptor; |
| |
| import org.apache.commons.lang.SystemUtils; |
| import org.apache.hadoop.classification.InterfaceAudience; |
| import org.apache.hadoop.classification.InterfaceStability; |
| import org.slf4j.Logger; |
| import org.slf4j.LoggerFactory; |
| |
| /** |
| * A factory for creating shared file descriptors inside a given directory. |
| * Typically, the directory will be /dev/shm or /tmp. |
| * |
| * We will hand out file descriptors that correspond to unlinked files residing |
| * in that directory. These file descriptors are suitable for sharing across |
| * multiple processes and are both readable and writable. |
| * |
| * Because we unlink the temporary files right after creating them, a JVM crash |
| * usually does not leave behind any temporary files in the directory. However, |
| * it may happen that we crash right after creating the file and before |
| * unlinking it. In the constructor, we attempt to clean up after any such |
| * remnants by trying to unlink any temporary files created by previous |
| * SharedFileDescriptorFactory instances that also used our prefix. |
| */ |
| @InterfaceAudience.Private |
| @InterfaceStability.Unstable |
| public class SharedFileDescriptorFactory { |
| public static final Logger LOG = |
| LoggerFactory.getLogger(SharedFileDescriptorFactory.class); |
| private final String prefix; |
| private final String path; |
| |
| public static String getLoadingFailureReason() { |
| if (!NativeIO.isAvailable()) { |
| return "NativeIO is not available."; |
| } |
| if (!SystemUtils.IS_OS_UNIX) { |
| return "The OS is not UNIX."; |
| } |
| return null; |
| } |
| |
| /** |
| * Create a new SharedFileDescriptorFactory. |
| * |
| * @param prefix The prefix to prepend to all the file names created |
| * by this factory. |
| * @param paths An array of paths to use. We will try each path in |
| * succession, and return a factory using the first |
| * usable path. |
| * @return The factory. |
| * @throws IOException If a factory could not be created for any reason. |
| */ |
| public static SharedFileDescriptorFactory create(String prefix, |
| String paths[]) throws IOException { |
| String loadingFailureReason = getLoadingFailureReason(); |
| if (loadingFailureReason != null) { |
| throw new IOException(loadingFailureReason); |
| } |
| if (paths.length == 0) { |
| throw new IOException("no SharedFileDescriptorFactory paths were " + |
| "configured."); |
| } |
| StringBuilder errors = new StringBuilder(); |
| String strPrefix = ""; |
| for (String path : paths) { |
| try { |
| FileInputStream fis = |
| new FileInputStream(createDescriptor0(prefix + "test", path, 1)); |
| fis.close(); |
| deleteStaleTemporaryFiles0(prefix, path); |
| return new SharedFileDescriptorFactory(prefix, path); |
| } catch (IOException e) { |
| errors.append(strPrefix).append("Error creating file descriptor in "). |
| append(path).append(": ").append(e.getMessage()); |
| strPrefix = ", "; |
| } |
| } |
| throw new IOException(errors.toString()); |
| } |
| |
| /** |
| * Create a SharedFileDescriptorFactory. |
| * |
| * @param prefix Prefix to add to all file names we use. |
| * @param path Path to use. |
| */ |
| private SharedFileDescriptorFactory(String prefix, String path) { |
| this.prefix = prefix; |
| this.path = path; |
| } |
| |
| public String getPath() { |
| return path; |
| } |
| |
| /** |
| * Create a shared file descriptor which will be both readable and writable. |
| * |
| * @param info Information to include in the path of the |
| * generated descriptor. |
| * @param length The starting file length. |
| * |
| * @return The file descriptor, wrapped in a FileInputStream. |
| * @throws IOException If there was an I/O or configuration error creating |
| * the descriptor. |
| */ |
| public FileInputStream createDescriptor(String info, int length) |
| throws IOException { |
| return new FileInputStream( |
| createDescriptor0(prefix + info, path, length)); |
| } |
| |
| /** |
| * Delete temporary files in the directory, NOT following symlinks. |
| */ |
| private static native void deleteStaleTemporaryFiles0(String prefix, |
| String path) throws IOException; |
| |
| /** |
| * Create a file with O_EXCL, and then resize it to the desired size. |
| */ |
| private static native FileDescriptor createDescriptor0(String prefix, |
| String path, int length) throws IOException; |
| } |