org.apache.jackrabbit.core.fs.local.HandleMonitor Maven / Gradle / Ivy
/*
* 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.jackrabbit.core.fs.local;
import org.apache.jackrabbit.util.LazyFileInputStream;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.util.HashMap;
import java.util.HashSet;
/**
* This Class implements a very simple open handle monitor for the local
* file system. This is usefull, if the list of open handles, referenced by
* an open FileInputStream() should be tracked. This can cause problems on
* windows filesystems where open files cannot be deleted.
*/
public class HandleMonitor {
/**
* The default logger
*/
private static Logger log = LoggerFactory.getLogger(HandleMonitor.class);
/**
* the map of open handles (key=File, value=Handle)
*/
private HashMap openHandles = new HashMap();
/**
* Opens a file and returns an InputStream
*
* @param file
* @return
* @throws FileNotFoundException
*/
public InputStream open(File file) throws FileNotFoundException {
Handle handle = getHandle(file);
InputStream in = handle.open();
return in;
}
/**
* Checks, if the file is open
* @param file
* @return
*/
public boolean isOpen(File file) {
return openHandles.containsKey(file);
}
/**
* Closes a file
* @param file
*/
private void close(File file) {
openHandles.remove(file);
}
/**
* Returns the handle for a file.
* @param file
* @return
*/
private Handle getHandle(File file) {
Handle handle = openHandles.get(file);
if (handle == null) {
handle = new Handle(file);
openHandles.put(file, handle);
}
return handle;
}
/**
* Dumps the contents of this monitor
*/
public void dump() {
log.info("Number of open files: " + openHandles.size());
for (File file : openHandles.keySet()) {
Handle handle = openHandles.get(file);
handle.dump();
}
}
/**
* Dumps the information for a file
* @param file
*/
public void dump(File file) {
Handle handle = openHandles.get(file);
if (handle != null) {
handle.dump(true);
}
}
/**
* Class representing all open handles to a file
*/
private class Handle {
/**
* the file of this handle
*/
private File file;
/**
* all open streams of this handle
*/
private HashSet streams = new HashSet();
/**
* Creates a new handle for a file
* @param file
*/
private Handle(File file) {
this.file = file;
}
/**
* opens a stream for this handle
* @return
* @throws FileNotFoundException
*/
private InputStream open() throws FileNotFoundException {
Handle.MonitoredInputStream in = new Handle.MonitoredInputStream(file);
streams.add(in);
return in;
}
/**
* Closes a stream
* @param in
*/
private void close(MonitoredInputStream in) {
streams.remove(in);
if (streams.isEmpty()) {
HandleMonitor.this.close(file);
}
}
/**
* Dumps this handle
*/
private void dump() {
dump(false);
}
/**
* Dumps this handle
*/
private void dump(boolean detailed) {
if (detailed) {
log.info("- " + file.getPath() + ", " + streams.size());
for (Handle.MonitoredInputStream in : streams) {
in.dump();
}
} else {
log.info("- " + file.getPath() + ", " + streams.size());
}
}
/**
* Delegating input stream that registers/unregisters itself from the
* handle.
*/
private class MonitoredInputStream extends LazyFileInputStream {
/**
* throwable of the time, the stream was created
*/
private final Throwable throwable = new Exception();
/**
* {@inheritDoc}
*/
private MonitoredInputStream(File file) throws FileNotFoundException {
super(file);
}
/**
* dumps this stream
*/
private void dump() {
log.info("- opened by : ", throwable);
}
/**
* {@inheritDoc}
*/
public void close() throws IOException {
// remove myself from the set
Handle.this.close(this);
super.close();
}
}
}
}