/*
* 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.tika.fork;
import java.io.ByteArrayInputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.NotSerializableException;
import java.io.OutputStream;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.net.URL;
import java.util.zip.CheckedInputStream;
import java.util.zip.CheckedOutputStream;
import java.util.zip.Checksum;
import org.apache.tika.exception.TikaException;
class ForkServer implements Runnable, Checksum {
public static final byte ERROR = -1;
public static final byte DONE = 0;
public static final byte CALL = 1;
public static final byte PING = 2;
public static final byte RESOURCE = 3;
public static final byte READY = 4;
//milliseconds to sleep before checking to see if there has been any reading/writing
//If no reading or writing in this time, shutdown the server.
private long serverPulseMillis = 5000;
/**
* Starts a forked server process using the standard input and output
* streams for communication with the parent process. Any attempts by
* stray code to read from standard input or write to standard output
* is redirected to avoid interfering with the communication channel.
*
* @param args command line arguments, ignored
* @throws Exception if the server could not be started
*/
public static void main(String[] args) throws Exception {
long serverPulseMillis = -1;
if (args.length > 0) {
serverPulseMillis = Long.parseLong(args[0]);
}
URL.setURLStreamHandlerFactory(new MemoryURLStreamHandlerFactory());
ForkServer server = new ForkServer(System.in, System.out, serverPulseMillis);
System.setIn(new ByteArrayInputStream(new byte[0]));
System.setOut(System.err);
Thread watchdog = new Thread(server, "Tika Watchdog");
watchdog.setDaemon(true);
watchdog.start();
server.processRequests();
}
/** Input stream for reading from the parent process */
private final DataInputStream input;
/** Output stream for writing to the parent process */
private final DataOutputStream output;
private volatile boolean active = true;
/**
* Sets up a forked server instance using the given stdin/out
* communication channel.
*
* @param input input stream for reading from the parent process
* @param output output stream for writing to the parent process
* @throws IOException if the server instance could not be created
*/
public ForkServer(InputStream input, OutputStream output, long serverPulseMillis)
throws IOException {
this.input =
new DataInputStream(new CheckedInputStream(input, this));
this.output =
new DataOutputStream(new CheckedOutputStream(output, this));
this.serverPulseMillis = serverPulseMillis;
}
public void run() {
try {
while (active) {
active = false;
Thread.sleep(serverPulseMillis);
}
System.exit(0);
} catch (InterruptedException e) {
}
}
public void processRequests() {
try {
output.writeByte(READY);
output.flush();
ClassLoader loader = (ClassLoader) readObject(
ForkServer.class.getClassLoader());
Thread.currentThread().setContextClassLoader(loader);
Object object = readObject(loader);
while (true) {
int request = input.read();
if (request == -1) {
break;
} else if (request == PING) {
output.writeByte(PING);
} else if (request == CALL) {
call(loader, object);
} else {
throw new IllegalStateException("Unexpected request");
}
output.flush();
}
} catch (Throwable t) {
t.printStackTrace();
}
System.err.flush();
}
private void call(ClassLoader loader, Object object) throws Exception {
Method method = getMethod(object, input.readUTF());
Object[] args =
new Object[method.getParameterTypes().length];
for (int i = 0; i < args.length; i++) {
args[i] = readObject(loader);
}
try {
method.invoke(object, args);
output.write(DONE);
} catch (InvocationTargetException e) {
output.write(ERROR);
// Try to send the underlying Exception itself
Throwable toSend = e.getCause();
try {
ForkObjectInputStream.sendObject(toSend, output);
} catch (NotSerializableException nse) {
// Need to build a serializable version of it
TikaException te = new TikaException( toSend.getMessage() );
te.setStackTrace( toSend.getStackTrace() );
ForkObjectInputStream.sendObject(te, output);
}
}
}
private Method getMethod(Object object, String name) {
Class<?> klass = object.getClass();
while (klass != null) {
for (Class<?> iface : klass.getInterfaces()) {
for (Method method : iface.getMethods()) {
if (name.equals(method.getName())) {
return method;
}
}
}
klass = klass.getSuperclass();
}
return null;
}
/**
* Deserializes an object from the given stream. The serialized object
* is expected to be preceded by a size integer, that is used for reading
* the entire serialization into a memory before deserializing it.
*
* @param input input stream from which the serialized object is read
* @param loader class loader to be used for loading referenced classes
* @throws IOException if the object could not be deserialized
* @throws ClassNotFoundException if a referenced class is not found
*/
private Object readObject(ClassLoader loader)
throws IOException, ClassNotFoundException {
Object object = ForkObjectInputStream.readObject(input, loader);
if (object instanceof ForkProxy) {
((ForkProxy) object).init(input, output);
}
// Tell the parent process that we successfully received this object
output.writeByte(ForkServer.DONE);
output.flush();
return object;
}
//------------------------------------------------------------< Checksum >
public void update(int b) {
active = true;
}
public void update(byte[] b, int off, int len) {
active = true;
}
public long getValue() {
return 0;
}
public void reset() {
}
}