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      1 /*
      2  * Copyright (C) 2017 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 package com.android.layoutlib.bridge.remote.server;
     18 
     19 import com.android.layout.remote.api.RemoteBridge;
     20 import com.android.tools.layoutlib.annotations.NotNull;
     21 
     22 import java.io.BufferedReader;
     23 import java.io.IOException;
     24 import java.io.InputStreamReader;
     25 import java.lang.management.ManagementFactory;
     26 import java.lang.management.RuntimeMXBean;
     27 import java.nio.file.Path;
     28 import java.nio.file.Paths;
     29 import java.rmi.NoSuchObjectException;
     30 import java.rmi.RemoteException;
     31 import java.rmi.registry.LocateRegistry;
     32 import java.rmi.registry.Registry;
     33 import java.rmi.server.UnicastRemoteObject;
     34 import java.util.ArrayList;
     35 import java.util.List;
     36 import java.util.concurrent.ArrayBlockingQueue;
     37 import java.util.concurrent.BlockingQueue;
     38 import java.util.concurrent.TimeUnit;
     39 import java.util.stream.Collectors;
     40 
     41 /**
     42  * Main server class. The main method will start an RMI server for the {@link RemoteBridgeImpl}
     43  * class.
     44  */
     45 public class ServerMain {
     46     private static final String RUNNING_SERVER_STR = "Server is running on port ";
     47     public static int REGISTRY_BASE_PORT = 9000;
     48 
     49     private final int mPort;
     50     private final Registry mRegistry;
     51 
     52     private ServerMain(int port, @NotNull Registry registry) {
     53         mPort = port;
     54         mRegistry = registry;
     55     }
     56 
     57     public int getPort() {
     58         return mPort;
     59     }
     60 
     61     public void stop() {
     62         try {
     63             UnicastRemoteObject.unexportObject(mRegistry, true);
     64         } catch (NoSuchObjectException ignored) {
     65         }
     66     }
     67 
     68     /**
     69      * This will start a new JVM and connect to the new JVM RMI registry.
     70      * <p/>
     71      * The server will start looking for ports available for the {@link Registry} until a free one
     72      * is found. The port number will be returned.
     73      * If no ports are available, a {@link RemoteException} will be thrown.
     74      * @param basePort port number to start looking for available ports
     75      * @param limit number of ports to check. The last port to be checked will be (basePort + limit)
     76      */
     77     public static ServerMain forkAndStartServer(int basePort, int limit)
     78             throws IOException, InterruptedException {
     79         // We start a new VM by copying all the parameter that we received in the current VM.
     80         // We only remove the agentlib parameter since that could cause a port collision and avoid
     81         // the new VM from starting.
     82         RuntimeMXBean runtimeMxBean = ManagementFactory.getRuntimeMXBean();
     83         List<String> arguments = runtimeMxBean.getInputArguments().stream()
     84                 .filter(arg -> !arg.contains("-agentlib")) // Filter agentlib to avoid conflicts
     85                 .collect(Collectors.toList());
     86 
     87         Path javaPath = Paths.get(System.getProperty("java.home"), "bin", "java");
     88         String thisClassName = ServerMain.class.getName()
     89                 .replace('.','/');
     90 
     91         List<String> cmd = new ArrayList<>();
     92         cmd.add(javaPath.toString());
     93 
     94         // Inherited arguments
     95         cmd.addAll(arguments);
     96 
     97         // Classpath
     98         cmd.add("-cp");
     99         cmd.add(System.getProperty("java.class.path"));
    100 
    101         // Class name and path
    102         cmd.add(thisClassName);
    103 
    104         // ServerMain parameters [basePort. limit]
    105         cmd.add(Integer.toString(basePort));
    106         cmd.add(Integer.toString(limit));
    107 
    108         Process process = new ProcessBuilder()
    109                 .command(cmd)
    110                 .start();
    111 
    112         BlockingQueue<String> outputQueue = new ArrayBlockingQueue<>(10);
    113         Thread outputThread = new Thread(() -> {
    114             BufferedReader inputStream = new BufferedReader(
    115                     new InputStreamReader(process.getInputStream()));
    116             inputStream.lines()
    117                     .forEach(outputQueue::offer);
    118 
    119         });
    120         outputThread.setName("output thread");
    121         outputThread.start();
    122 
    123         Runnable killServer = () -> {
    124             process.destroyForcibly();
    125             outputThread.interrupt();
    126             try {
    127                 outputThread.join();
    128             } catch (InterruptedException ignore) {
    129             }
    130         };
    131 
    132         // Try to read the "Running on port" line in 10 lines. If it's not there just fail.
    133         for (int i = 0; i < 10; i++) {
    134             String line = outputQueue.poll(1000, TimeUnit.SECONDS);
    135 
    136             if (line.startsWith(RUNNING_SERVER_STR)) {
    137                 int runningPort = Integer.parseInt(line.substring(RUNNING_SERVER_STR.length()));
    138                 System.out.println("Running on port " + runningPort);
    139 
    140                 // We already know where the server is running so we just need to get the registry
    141                 // and return our own instance of ServerMain
    142                 Registry registry = LocateRegistry.getRegistry(runningPort);
    143                 return new ServerMain(runningPort, registry) {
    144                     @Override
    145                     public void stop() {
    146                         killServer.run();
    147                     }
    148                 };
    149             }
    150         }
    151 
    152         killServer.run();
    153         throw new IOException("Unable to find start string");
    154     }
    155 
    156     /**
    157      * The server will start looking for ports available for the {@link Registry} until a free one
    158      * is found. The port number will be returned.
    159      * If no ports are available, a {@link RemoteException} will be thrown.
    160      * @param basePort port number to start looking for available ports
    161      * @param limit number of ports to check. The last port to be checked will be (basePort + limit)
    162      */
    163     private static ServerMain startServer(int basePort, int limit) throws RemoteException {
    164         RemoteBridgeImpl remoteBridge = new RemoteBridgeImpl();
    165         RemoteBridge stub = (RemoteBridge) UnicastRemoteObject.exportObject(remoteBridge, 0);
    166 
    167         RemoteException lastException = null;
    168         for (int port = basePort; port <= basePort + limit; port++) {
    169             try {
    170                 Registry registry = LocateRegistry.createRegistry(port);
    171                 registry.rebind(RemoteBridge.class.getName(), stub);
    172                 return new ServerMain(port, registry);
    173             } catch (RemoteException e) {
    174                 lastException = e;
    175             }
    176         }
    177 
    178         if (lastException == null) {
    179             lastException = new RemoteException("Unable to start server");
    180         }
    181 
    182         throw lastException;
    183     }
    184 
    185     public static void main(String[] args) throws RemoteException {
    186         int basePort = args.length > 0 ? Integer.parseInt(args[0]) : REGISTRY_BASE_PORT;
    187         int limit = args.length > 1 ? Integer.parseInt(args[1]) : 10;
    188 
    189         ServerMain server = startServer(basePort, limit);
    190         System.out.println(RUNNING_SERVER_STR + server.getPort());
    191     }
    192 }
    193