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GUACAMOLE-267: Implement FailoverGuacamoleSocket.
This commit is contained in:
Michael Jumper
@@ -0,0 +1,347 @@
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/*
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* Licensed to the Apache Software Foundation (ASF) under one
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* or more contributor license agreements. See the NOTICE file
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* distributed with this work for additional information
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* regarding copyright ownership. The ASF licenses this file
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* to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance
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* with the License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing,
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* software distributed under the License is distributed on an
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* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
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* KIND, either express or implied. See the License for the
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* specific language governing permissions and limitations
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* under the License.
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*/
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package org.apache.guacamole.protocol;
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import java.util.List;
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import org.apache.guacamole.GuacamoleConnectionClosedException;
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import org.apache.guacamole.GuacamoleException;
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import org.apache.guacamole.GuacamoleServerException;
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import org.apache.guacamole.io.GuacamoleReader;
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import org.apache.guacamole.io.GuacamoleWriter;
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import org.apache.guacamole.net.GuacamoleSocket;
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import org.slf4j.Logger;
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import org.slf4j.LoggerFactory;
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/**
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* GuacamoleSocket implementation which transparently switches between an
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* underlying queue of available sockets when errors are encountered during
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* the initial part of a connection (prior to first "sync").
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*/
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public class FailoverGuacamoleSocket implements GuacamoleSocket {
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/**
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* Logger for this class.
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*/
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private Logger logger = LoggerFactory.getLogger(FailoverGuacamoleSocket.class);
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/**
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* A queue of available sockets. The full set of available sockets need not
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* be known ahead of time.
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*/
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public static interface SocketQueue {
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/**
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* Returns the next available socket in the queue, or null if no
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* further sockets are available. This function will be invoked when an
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* error occurs within the current socket, and will be invoked again if
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* a GuacamoleException is thrown. Such repeated calls to this function
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* will occur until errors cease or null is returned.
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*
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* @return
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* The next available socket in the queue, or null if no further
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* sockets are available.
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*
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* @throws GuacamoleException
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* If an error occurs preventing the next available socket from
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* being used.
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*/
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GuacamoleSocket nextSocket() throws GuacamoleException;
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}
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/**
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* The queue of available sockets provided when this FailoverGuacamoleSocket
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* was created.
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*/
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private final SocketQueue sockets;
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/**
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* The current socket being used, or null if no socket is available.
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*/
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private GuacamoleSocket socket;
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/**
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* Creates a new FailoverGuacamoleSocket which pulls its sockets from the
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* given SocketQueue. If an error occurs during the Guacamole connection,
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* other sockets from the SocketQueue are tried, in order, until no error
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* occurs.
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*
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* @param sockets
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* A SocketQueue which returns the sockets which should be used, in
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* order.
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*
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* @throws GuacamoleException
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* If errors prevent use of the sockets defined by the SocketQueue, and
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* no further sockets remain to be tried.
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*/
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public FailoverGuacamoleSocket(SocketQueue sockets)
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throws GuacamoleException {
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this.sockets = sockets;
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selectNextSocket();
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}
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private GuacamoleException tryNextSocket() {
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try {
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if (socket != null)
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socket.close();
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}
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catch (GuacamoleException e) {
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if (socket.isOpen())
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logger.debug("Previous failed socket could not be closed.", e);
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}
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try {
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socket = sockets.nextSocket();
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if (socket == null)
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return new GuacamoleServerException("No remaining sockets to try.");
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}
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catch (GuacamoleException e) {
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if (tryNextSocket() != null)
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return e;
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}
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return null;
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}
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private void selectNextSocket() throws GuacamoleException {
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synchronized (sockets) {
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GuacamoleException failure = tryNextSocket();
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if (failure != null)
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throw failure;
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}
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}
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private class ErrorFilter implements GuacamoleFilter {
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/**
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* Whether a "sync" instruction has been read.
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*/
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private boolean receivedSync = false;
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@Override
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public GuacamoleInstruction filter(GuacamoleInstruction instruction)
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throws GuacamoleException {
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// Ignore instructions after first sync is received
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if (receivedSync)
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return instruction;
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String opcode = instruction.getOpcode();
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if (opcode.equals("sync")) {
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receivedSync = true;
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return instruction;
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}
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if (opcode.equals("error"))
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return handleError(instruction);
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return instruction;
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}
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private GuacamoleInstruction handleError(GuacamoleInstruction instruction) {
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// Ignore error instructions which are missing the status code
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List<String> args = instruction.getArgs();
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if (args.size() < 2) {
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logger.debug("Ignoring \"error\" instruction without status code.");
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return instruction;
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}
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int statusCode;
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try {
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statusCode = Integer.parseInt(args.get(1));
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}
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catch (NumberFormatException e) {
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logger.debug("Ignoring \"error\" instruction with non-numeric status code.", e);
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return instruction;
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}
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// Invalid status code
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GuacamoleStatus status = GuacamoleStatus.fromGuacamoleStatusCode(statusCode);
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if (status == null) {
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logger.debug("Ignoring \"error\" instruction with unknown/invalid status code: {}", statusCode);
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return instruction;
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}
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// Only handle error instructions related to the upstream remote desktop
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switch (status) {
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// Transparently connect to a different connection if upstream fails
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case UPSTREAM_ERROR:
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case UPSTREAM_NOT_FOUND:
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case UPSTREAM_TIMEOUT:
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case UPSTREAM_UNAVAILABLE:
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break;
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// Allow error through otherwise
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default:
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return instruction;
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}
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logger.debug("Overriding {} \"error\" instruction. Failing over to next connection...", status);
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// Advance through remaining sockets until another functional socket
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// is retrieved, or no more sockets remain
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try {
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selectNextSocket();
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return null;
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}
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catch (GuacamoleException e) {
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logger.debug("No sockets remain to be tried - giving up on failover.");
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}
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// Allow error through if not intercepting
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return instruction;
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}
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}
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/**
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* GuacamoleReader which filters "error" instructions, transparently failing
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* over to the next socket in the queue if an error is encountered. Read
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* attempts are delegated to the GuacamoleReader of the current socket.
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*/
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private final GuacamoleReader reader = new FilteredGuacamoleReader(new GuacamoleReader() {
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@Override
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public boolean available() throws GuacamoleException {
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synchronized (sockets) {
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if (socket == null)
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return false;
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return socket.getReader().available();
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}
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}
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@Override
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public char[] read() throws GuacamoleException {
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synchronized (sockets) {
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if (socket == null)
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return null;
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return socket.getReader().read();
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}
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}
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@Override
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public GuacamoleInstruction readInstruction()
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throws GuacamoleException {
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synchronized (sockets) {
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if (socket == null)
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return null;
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return socket.getReader().readInstruction();
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}
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}
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}, new ErrorFilter());
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/**
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* GuacamoleWriter which delegates all write attempts to the GuacamoleWriter
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* of the current socket.
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*/
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private final GuacamoleWriter writer = new GuacamoleWriter() {
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@Override
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public void write(char[] chunk, int off, int len)
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throws GuacamoleException {
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synchronized (sockets) {
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if (socket == null)
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throw new GuacamoleConnectionClosedException("No further sockets remaining in SocketQueue.");
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socket.getWriter().write(chunk, off, len);
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}
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}
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@Override
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public void write(char[] chunk) throws GuacamoleException {
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synchronized (sockets) {
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if (socket == null)
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throw new GuacamoleConnectionClosedException("No further sockets remaining in SocketQueue.");
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socket.getWriter().write(chunk);
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}
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}
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@Override
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public void writeInstruction(GuacamoleInstruction instruction)
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throws GuacamoleException {
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synchronized (sockets) {
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if (socket == null)
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throw new GuacamoleConnectionClosedException("No further sockets remaining in SocketQueue.");
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socket.getWriter().writeInstruction(instruction);
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}
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}
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};
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@Override
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public GuacamoleReader getReader() {
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return reader;
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}
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@Override
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public GuacamoleWriter getWriter() {
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return writer;
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}
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@Override
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public void close() throws GuacamoleException {
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synchronized (sockets) {
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socket.close();
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}
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}
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@Override
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public boolean isOpen() {
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synchronized (sockets) {
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if (socket == null)
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return false;
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return socket.isOpen();
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}
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}
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}
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