static {
// dead-lock prevention.
//
// creating a new proxy class is a classloading activity, so it can create a dead-lock situation
// if thread A starts classloading via RemoteClassLoader.ladClass(),
// then thread B use JarCacheSupport.prefetch and tries to create a proxy for JarLoader
// (which blocks as Proxy.getProxyClass waits for RemoteClassLoader.defineClass lock by
// thread A)
// then thread A tries to touch JarLoader proxy (which blocks on thread B)
//
// to avoid situations like this, create proxy classes that we need during the classloading
jarLoaderProxy = RemoteInvocationHandler.getProxyClass(JarLoader.class);
}
/**
* Creates a new channel.
*
* @param name See {@link #Channel(String, ExecutorService, Mode, InputStream, OutputStream,
* OutputStream, boolean, ClassLoader)}
* @param exec See {@link #Channel(String, ExecutorService, Mode, InputStream, OutputStream,
* OutputStream, boolean, ClassLoader)}
* @param transport The transport that we run {@link Channel} on top of.
* @param base See {@link #Channel(String, ExecutorService, Mode, InputStream, OutputStream,
* OutputStream, boolean, ClassLoader)}
* @param restricted See {@link #Channel(String, ExecutorService, Mode, InputStream, OutputStream,
* OutputStream, boolean, ClassLoader)}
* @since 2.13
*/
public Channel(
String name,
ExecutorService exec,
CommandTransport transport,
boolean restricted,
ClassLoader base)
throws IOException {
this.name = name;
this.executor = new InterceptingExecutorService(exec);
this.isRestricted = restricted;
this.underlyingOutput = transport.getUnderlyingStream();
if (base == null) base = getClass().getClassLoader();
this.baseClassLoader = base;
if (export(this, false) != 1)
throw new AssertionError(); // export number 1 is reserved for the channel itself
remoteChannel = RemoteInvocationHandler.wrap(this, 1, IChannel.class, true, false);
this.remoteCapability = transport.getRemoteCapability();
this.pipeWriter = new PipeWriter(createPipeWriterExecutor());
this.transport = transport;
transport.setup(
this,
new CommandReceiver() {
public void handle(Command cmd) {
lastHeard = System.currentTimeMillis();
if (logger.isLoggable(Level.FINE)) logger.fine("Received " + cmd);
try {
cmd.execute(Channel.this);
} catch (Throwable t) {
logger.log(
Level.SEVERE,
"Failed to execute command " + cmd + " (channel " + Channel.this.name + ")",
t);
logger.log(Level.SEVERE, "This command is created here", cmd.createdAt);
}
}
public void terminate(IOException e) {
Channel.this.terminate(e);
}
});
}
/*package*/ Channel(ChannelBuilder settings, CommandTransport transport) throws IOException {
this.name = settings.getName();
this.executor = new InterceptingExecutorService(settings.getExecutors());
this.isRestricted = settings.isRestricted();
this.underlyingOutput = transport.getUnderlyingStream();
this.jarCache = settings.getJarCache();
this.baseClassLoader = settings.getBaseLoader();
if (export(this, false) != 1)
throw new AssertionError(); // export number 1 is reserved for the channel itself
remoteChannel = RemoteInvocationHandler.wrap(this, 1, IChannel.class, true, false);
this.remoteCapability = transport.getRemoteCapability();
this.pipeWriter = new PipeWriter(createPipeWriterExecutor());
this.transport = transport;
this.jarLoader =
new JarLoaderImpl(); // TODO: figure out a mechanism to allow the user to share this across
// Channels
setProperty(JarLoader.OURS, export(JarLoader.class, jarLoader, false));
transport.setup(
this,
new CommandReceiver() {
public void handle(Command cmd) {
lastHeard = System.currentTimeMillis();
if (logger.isLoggable(Level.FINE)) logger.fine("Received " + cmd);
try {
cmd.execute(Channel.this);
} catch (Throwable t) {
logger.log(
Level.SEVERE,
"Failed to execute command " + cmd + " (channel " + Channel.this.name + ")",
t);
logger.log(Level.SEVERE, "This command is created here", cmd.createdAt);
}
}
public void terminate(IOException e) {
Channel.this.terminate(e);
}
});
}
/**
* @param userProxy If true, the returned proxy will be capable to handle classes defined in the
* user classloader as parameters and return values. Such proxy relies on {@link
* RemoteClassLoader} and related mechanism, so it's not usable for implementing lower-layer
* services that are used by {@link RemoteClassLoader}.
* <p>To create proxies for objects inside remoting, pass in false.
*/
/*package*/ <T> T export(Class<T> type, T instance, boolean userProxy) {
if (instance == null) return null;
// every so often perform GC on the remote system so that
// unused RemoteInvocationHandler get released, which triggers
// unexport operation.
if ((++gcCounter) % 10000 == 0)
try {
send(new GCCommand());
} catch (IOException e) {
// for compatibility reason we can't change the export method signature
logger.log(Level.WARNING, "Unable to send GC command", e);
}
// either local side will auto-unexport, or the remote side will unexport when it's GC-ed
boolean autoUnexportByCaller = exportedObjects.isRecording();
final int id = export(instance, autoUnexportByCaller);
return RemoteInvocationHandler.wrap(null, id, type, userProxy, autoUnexportByCaller);
}
@SuppressWarnings("unchecked")
private synchronized void checkReply()
{
if (mc.hasReply()) {
Message m = mc.getReply();
if (m instanceof Error)
error = ((Error) m).getException();
else if (m instanceof MethodReturn) {
try {
rval = (ReturnType) RemoteInvocationHandler.convertRV(m.getSig(), m.getParameters(), me, conn);
} catch (DBusExecutionException DBEe) {
error = DBEe;
} catch (DBusException DBe) {
if (AbstractConnection.EXCEPTION_DEBUG && Debug.debug) Debug.print(Debug.ERR, DBe);
error = new DBusExecutionException(DBe.getMessage());
}
}
}
}
