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ehenomaehenoma
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Add proof of concept
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‎.gitignore‎

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build
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out
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*.class
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*.jar
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.idea
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*.iml
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.DS_Store
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.AppleDouble
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.LSOverride

‎README.md‎

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# Java Fork Demo
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Proof of concept application that dynamically creates virtual machines to
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execute tasks.
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`./run.sh` *Requires Java 16+*

‎run.sh‎

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javac ./src/Box.java ./src/Controller.java
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jar --create --file ./src/box.jar --main-class Box -C src Box.class
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java -cp src Controller "$@"

‎src/Box.java‎

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import java.io.IOException;
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import java.net.InetSocketAddress;
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import java.net.Socket;
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import java.nio.ByteBuffer;
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import java.nio.file.Files;
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import java.nio.file.Path;
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import java.time.Duration;
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import java.util.UUID;
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final class Box {
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private final UUID id;
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private final InetSocketAddress controllerAddress;
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private final Duration connectTimeout;
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private Socket connection;
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private Box(
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UUID id,
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InetSocketAddress controllerAddress,
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Duration connectTimeout
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) {
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this.id = id;
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this.connectTimeout = connectTimeout;
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this.controllerAddress = controllerAddress;
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}
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public void start() throws IOException {
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connect();
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try {
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advertise();
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accept();
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} finally {
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connection.close();
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}
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}
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private void connect() throws IOException {
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connection = new Socket();
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connection.connect(controllerAddress, (int) connectTimeout.toMillis());
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}
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public void advertise() throws IOException {
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var bytes = ByteBuffer.allocate(Long.SIZE * 2);
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bytes.putLong(id.getMostSignificantBits());
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bytes.putLong(id.getLeastSignificantBits());
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connection.getOutputStream().write(bytes.flip().array());
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}
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public void accept() throws IOException {
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var input = connection.getInputStream();
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byte[] buffer = new byte[4096];
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while (!Thread.currentThread().isInterrupted() && connection.isConnected()) {
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int read = input.read(buffer);
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if (read == -1) {
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return;
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}
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if (read != 0) {
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System.out.write(buffer, 0, read);
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}
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}
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}
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public static void main(String[] arguments) throws IOException {
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validateArguments(arguments);
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var box = createBoxFromArguments(arguments);
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Files.writeString(Path.of(box.id.toString() + ".box.txt"), box.id.toString());
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try {
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box.start();
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} catch (IOException failure) {
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System.err.println("error occurred while running box");
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failure.printStackTrace();
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}
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}
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private static void validateArguments(String[] arguments) {
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if (arguments.length != addressIndex + 1) {
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System.out.println("usage: box <id> <controllerAddress>");
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System.exit(-1);
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}
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}
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private static final int idIndex = 0;
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private static final int addressIndex = 1;
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private static Box createBoxFromArguments(String[] arguments) {
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var id = UUID.fromString(arguments[idIndex]);
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var address = parseAddress(arguments[addressIndex]);
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return new Box(id, address, Duration.ofMillis(5000));
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}
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private static InetSocketAddress parseAddress(String input) {
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int portSeparator = input.indexOf(':');
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if (portSeparator == -1) {
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throw new IllegalArgumentException("port missing: " + input);
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}
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int port = Integer.parseInt(input.substring(portSeparator + 1));
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var host = input.substring(0, portSeparator);
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return host.isEmpty()
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? new InetSocketAddress(port)
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: new InetSocketAddress(host, port);
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}
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}

‎src/Controller.java‎

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import java.io.IOException;
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import java.io.InputStream;
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import java.io.OutputStream;
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import java.net.InetSocketAddress;
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import java.net.ServerSocket;
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import java.net.Socket;
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import java.nio.ByteBuffer;
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import java.nio.charset.StandardCharsets;
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import java.util.UUID;
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import java.util.concurrent.Executor;
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import java.util.concurrent.Executors;
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import java.util.concurrent.ThreadLocalRandom;
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final class Controller {
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private final int port;
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private final String boxBinaryPath;
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private final Executor executor;
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private ServerSocket socket;
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private Controller(int port, String boxBinaryPath, Executor executor) {
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this.port = port;
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this.boxBinaryPath = boxBinaryPath;
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this.executor = executor;
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}
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public void start() throws IOException {
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socket = new ServerSocket();
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socket.bind(new InetSocketAddress(port));
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try {
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listen();
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} finally {
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socket.close();
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}
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}
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private void listen() throws IOException {
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while (!Thread.currentThread().isInterrupted() && socket.isBound()) {
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var client = socket.accept();
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executor.execute(() -> {
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try {
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accept(client);
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} catch (IOException failure) {
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System.err.println(
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"encountered error while serving " + client.getRemoteSocketAddress()
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);
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failure.printStackTrace();
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}
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});
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}
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}
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private void accept(Socket client) throws IOException {
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var input = client.getInputStream();
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byte[] initialPacket = input.readNBytes(Long.SIZE * 2);
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var id = readId(initialPacket);
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System.err.println("accepted client with id " + id);
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useBox(client);
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client.close();
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}
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private static final String[] firstNames = {
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"Leonard", "Lionel", "Elton", "Nina", "Art", "Tracy", "Freddy",
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};
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private static final String[] lastNames = {
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"Cohen", "Richie", "John", "Simone", "Garfunkel", "Chapman", "Mercury"
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};
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private void useBox(Socket client) throws IOException {
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var payload = createPayload();
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client.getOutputStream().write(payload);
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}
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private byte[] createPayload() {
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var random = ThreadLocalRandom.current();
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var firstName = firstNames[random.nextInt(firstNames.length)];
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var lastName = lastNames[random.nextInt(lastNames.length)];
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var fullName = firstName + " " + lastName;
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return fullName.getBytes(StandardCharsets.UTF_8);
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}
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private UUID readId(byte[] bytes) {
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var buffer = ByteBuffer.wrap(bytes);
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return new UUID(
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buffer.getLong(),
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buffer.getLong()
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);
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}
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public void startBox(UUID id) throws IOException {
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System.err.println("starting box " + id);
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var process = startBoxProcess();
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executor.execute(() -> {
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redirectBoxOutput(id, process);
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redirectBoxErrors(id, process);
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});
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}
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private void redirectBoxOutput(UUID id, Process process) {
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var prefix = "%s: ".formatted(id).getBytes(StandardCharsets.UTF_8);
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var suffix = "\r\n".getBytes(StandardCharsets.UTF_8);
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try {
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redirect(prefix, suffix, process.getInputStream(), System.out);
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} catch (IOException failedRedirect) {
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System.err.println("encountered error while redirecting " + id);
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failedRedirect.printStackTrace();
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}
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}
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private void redirectBoxErrors(UUID id, Process process) {
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var prefix = "Error in %s: ".formatted(id).getBytes(StandardCharsets.UTF_8);
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var suffix = "\r\n".getBytes(StandardCharsets.UTF_8);
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try {
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redirect(prefix, suffix, process.getErrorStream(), System.out);
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} catch (IOException failedRedirect) {
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System.err.println("encountered error while redirecting " + id);
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failedRedirect.printStackTrace();
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}
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}
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private static final String boxMemory = System.getProperty("box.memory", "2M");
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private Process startBoxProcess() throws IOException {
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var ownAddress = ":" + port;
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return new ProcessBuilder()
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.command(
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"java",
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"-Xmx%s".formatted(boxMemory),
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"-Xms%s".formatted(boxMemory),
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"-XX:+UseSerialGC",
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/* program */ "-jar", boxBinaryPath,
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/* arguments */ UUID.randomUUID().toString(), ownAddress
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).start();
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}
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private static void redirect(
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byte[] prefix,
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byte[] suffix,
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InputStream input,
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OutputStream output
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) throws IOException {
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byte[] buffer = new byte[1024];
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int read;
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while ((read = input.read(buffer)) != -1) {
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synchronized (output) {
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output.write(prefix);
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output.write(buffer, 0, read);
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output.write(suffix);
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}
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}
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}
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// All logging is done to System.err since output is redirected to System.out
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public static void main(String[] arguments) throws InterruptedException {
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validateArguments(arguments);
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var executor = Executors.newCachedThreadPool();
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var controller = new Controller(3_1337, arguments[0], executor);
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runController(executor, controller);
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int boxCount = arguments.length > 1 ? Integer.parseInt(arguments[1]) : 3;
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startSomeBoxes(controller, boxCount);
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Thread.sleep(10_000);
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executor.shutdown();
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}
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private static void runController(Executor executor, Controller controller) {
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executor.execute(() -> {
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try {
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controller.start();
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} catch (IOException failure) {
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System.err.println("encountered error in controller");
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failure.printStackTrace();
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}
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});
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}
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private static void startSomeBoxes(Controller controller, int count) {
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try {
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for (int index = 0; index < count; index++) {
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controller.startBox(UUID.randomUUID());
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}
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} catch (IOException failure) {
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System.err.println("failed to start boxes");
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}
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}
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private static void validateArguments(String[] arguments) {
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if (arguments.length < 1) {
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System.err.println("usage: ./run <path-to-box-binary> [box-count]");
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System.exit(-1);
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}
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}
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}

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