/*
* Licensed to Elasticsearch under one or more contributor
* license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright
* ownership. Elasticsearch 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.elasticsearch.watcher;
import org.apache.logging.log4j.Logger;
import org.elasticsearch.common.io.FileSystemUtils;
import org.elasticsearch.common.logging.Loggers;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.attribute.BasicFileAttributes;
import java.util.Arrays;
/**
* File resources watcher
*
* The file watcher checks directory and all its subdirectories for file changes and notifies its listeners accordingly
*/
public class FileWatcher extends AbstractResourceWatcher<FileChangesListener> {
private FileObserver rootFileObserver;
private Path file;
private static final Logger logger = Loggers.getLogger(FileWatcher.class);
/**
* Creates new file watcher on the given directory
*/
public FileWatcher(Path file) {
this.file = file;
rootFileObserver = new FileObserver(file);
}
/**
* Clears any state with the FileWatcher, making all files show up as new
*/
public void clearState() {
rootFileObserver = new FileObserver(file);
try {
rootFileObserver.init(false);
} catch (IOException e) {
// ignore IOException
}
}
@Override
protected void doInit() throws IOException {
rootFileObserver.init(true);
}
@Override
protected void doCheckAndNotify() throws IOException {
rootFileObserver.checkAndNotify();
}
private static FileObserver[] EMPTY_DIRECTORY = new FileObserver[0];
private class FileObserver {
private Path file;
private boolean exists;
private long length;
private long lastModified;
private boolean isDirectory;
private FileObserver[] children;
FileObserver(Path file) {
this.file = file;
}
public void checkAndNotify() throws IOException {
boolean prevExists = exists;
boolean prevIsDirectory = isDirectory;
long prevLength = length;
long prevLastModified = lastModified;
exists = Files.exists(file);
// TODO we might use the new NIO2 API to get real notification?
if (exists) {
BasicFileAttributes attributes = Files.readAttributes(file, BasicFileAttributes.class);
isDirectory = attributes.isDirectory();
if (isDirectory) {
length = 0;
lastModified = 0;
} else {
length = attributes.size();
lastModified = attributes.lastModifiedTime().toMillis();
}
} else {
isDirectory = false;
length = 0;
lastModified = 0;
}
// Perform notifications and update children for the current file
if (prevExists) {
if (exists) {
if (isDirectory) {
if (prevIsDirectory) {
// Remained a directory
updateChildren();
} else {
// File replaced by directory
onFileDeleted();
onDirectoryCreated(false);
}
} else {
if (prevIsDirectory) {
// Directory replaced by file
onDirectoryDeleted();
onFileCreated(false);
} else {
// Remained file
if (prevLastModified != lastModified || prevLength != length) {
onFileChanged();
}
}
}
} else {
// Deleted
if (prevIsDirectory) {
onDirectoryDeleted();
} else {
onFileDeleted();
}
}
} else {
// Created
if (exists) {
if (isDirectory) {
onDirectoryCreated(false);
} else {
onFileCreated(false);
}
}
}
}
private void init(boolean initial) throws IOException {
exists = Files.exists(file);
if (exists) {
BasicFileAttributes attributes = Files.readAttributes(file, BasicFileAttributes.class);
isDirectory = attributes.isDirectory();
if (isDirectory) {
onDirectoryCreated(initial);
} else {
length = attributes.size();
lastModified = attributes.lastModifiedTime().toMillis();
onFileCreated(initial);
}
}
}
private FileObserver createChild(Path file, boolean initial) throws IOException {
FileObserver child = new FileObserver(file);
child.init(initial);
return child;
}
private Path[] listFiles() throws IOException {
final Path[] files = FileSystemUtils.files(file);
Arrays.sort(files);
return files;
}
private FileObserver[] listChildren(boolean initial) throws IOException {
Path[] files = listFiles();
if (files != null && files.length > 0) {
FileObserver[] children = new FileObserver[files.length];
for (int i = 0; i < files.length; i++) {
children[i] = createChild(files[i], initial);
}
return children;
} else {
return EMPTY_DIRECTORY;
}
}
private void updateChildren() throws IOException {
Path[] files = listFiles();
if (files != null && files.length > 0) {
FileObserver[] newChildren = new FileObserver[files.length];
int child = 0;
int file = 0;
while (file < files.length || child < children.length ) {
int compare;
if (file >= files.length) {
compare = -1;
} else if (child >= children.length) {
compare = 1;
} else {
compare = children[child].file.compareTo(files[file]);
}
if (compare == 0) {
// Same file copy it and update
children[child].checkAndNotify();
newChildren[file] = children[child];
file++;
child++;
} else {
if (compare > 0) {
// This child doesn't appear in the old list - init it
newChildren[file] = createChild(files[file], false);
file++;
} else {
// The child from the old list is missing in the new list
// Delete it
deleteChild(child);
child++;
}
}
}
children = newChildren;
} else {
// No files - delete all children
for (int child = 0; child < children.length; child++) {
deleteChild(child);
}
children = EMPTY_DIRECTORY;
}
}
private void deleteChild(int child) {
if (children[child].exists) {
if (children[child].isDirectory) {
children[child].onDirectoryDeleted();
} else {
children[child].onFileDeleted();
}
}
}
private void onFileCreated(boolean initial) {
for (FileChangesListener listener : listeners()) {
try {
if (initial) {
listener.onFileInit(file);
} else {
listener.onFileCreated(file);
}
} catch (Exception e) {
logger.warn("cannot notify file changes listener", e);
}
}
}
private void onFileDeleted() {
for (FileChangesListener listener : listeners()) {
try {
listener.onFileDeleted(file);
} catch (Exception e) {
logger.warn("cannot notify file changes listener", e);
}
}
}
private void onFileChanged() {
for (FileChangesListener listener : listeners()) {
try {
listener.onFileChanged(file);
} catch (Exception e) {
logger.warn("cannot notify file changes listener", e);
}
}
}
private void onDirectoryCreated(boolean initial) throws IOException {
for (FileChangesListener listener : listeners()) {
try {
if (initial) {
listener.onDirectoryInit(file);
} else {
listener.onDirectoryCreated(file);
}
} catch (Exception e) {
logger.warn("cannot notify file changes listener", e);
}
}
children = listChildren(initial);
}
private void onDirectoryDeleted() {
// First delete all children
for (int child = 0; child < children.length; child++) {
deleteChild(child);
}
for (FileChangesListener listener : listeners()) {
try {
listener.onDirectoryDeleted(file);
} catch (Exception e) {
logger.warn("cannot notify file changes listener", e);
}
}
}
}
}