关于arthas:聊聊arthas的HttpTermServer

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本文次要钻研一下 arthas 的 HttpTermServer

com/taobao/arthas/core/shell/term/TermServer.java

public abstract class TermServer {

    /**
     * Create a term server for the Telnet protocol.
     *
     * @param configure
     * @return the term server
     */
    public static TermServer createTelnetTermServer(Configure configure, ShellServerOptions options) {int port = configure.getTelnetPort() != null ? configure.getTelnetPort() : ArthasConstants.TELNET_PORT;
        return new TelnetTermServer(configure.getIp(), port, options.getConnectionTimeout());
    }

    /**
     * Create a term server for the HTTP protocol, using an existing router.
     *
     * @return the term server
     */
    public static TermServer createHttpTermServer() {
        // TODO
        return null;
    }

    /**
     * Set the term handler that will receive incoming client connections. When a remote terminal connects
     * the {@code handler} will be called with the {@link Term} which can be used to interact with the remote
     * terminal.
     *
     * @param handler the term handler
     * @return this object
     */
    public abstract TermServer termHandler(Handler<Term> handler);

    /**
     * Bind the term server, the {@link #termHandler(Handler)} must be set before.
     *
     * @return this object
     */
    public TermServer listen() {return listen(null);
    }

    /**
     * Bind the term server, the {@link #termHandler(Handler)} must be set before.
     *
     * @param listenHandler the listen handler
     * @return this object
     */
    public abstract TermServer listen(Handler<Future<TermServer>> listenHandler);

    /**
     * The actual port the server is listening on. This is useful if you bound the server specifying 0 as port number
     * signifying an ephemeral port
     *
     * @return the actual port the server is listening on.
     */
    public abstract int actualPort();

    /**
     * Close the server. This will close any currently open connections. The close may not complete until after this
     * method has returned.
     */
    public abstract void close();

    /**
     * Like {@link #close} but supplying a handler that will be notified when close is complete.
     *
     * @param completionHandler the handler to be notified when the term server is closed
     */
    public abstract void close(Handler<Future<Void>> completionHandler);

}

TermServer 是一个抽象类，它定义了 termHandler、listen、actualPort、close 形象办法

com/taobao/arthas/core/shell/term/impl/HttpTermServer.java

public class HttpTermServer extends TermServer {private static final Logger logger = LoggerFactory.getLogger(HttpTermServer.class);

    private Handler<Term> termHandler;
    private NettyWebsocketTtyBootstrap bootstrap;
    private String hostIp;
    private int port;
    private long connectionTimeout;
    private EventExecutorGroup workerGroup;
    private HttpSessionManager httpSessionManager;

    public HttpTermServer(String hostIp, int port, long connectionTimeout, EventExecutorGroup workerGroup, HttpSessionManager httpSessionManager) {
        this.hostIp = hostIp;
        this.port = port;
        this.connectionTimeout = connectionTimeout;
        this.workerGroup = workerGroup;
        this.httpSessionManager = httpSessionManager;
    }

    @Override
    public TermServer termHandler(Handler<Term> handler) {
        this.termHandler = handler;
        return this;
    }

    @Override
    public TermServer listen(Handler<Future<TermServer>> listenHandler) {
        // TODO: charset and inputrc from options
        bootstrap = new NettyWebsocketTtyBootstrap(workerGroup, httpSessionManager).setHost(hostIp).setPort(port);
        try {bootstrap.start(new Consumer<TtyConnection>() {
                @Override
                public void accept(final TtyConnection conn) {termHandler.handle(new TermImpl(Helper.loadKeymap(), conn));
                }
            }).get(connectionTimeout, TimeUnit.MILLISECONDS);
            listenHandler.handle(Future.<TermServer>succeededFuture());
        } catch (Throwable t) {logger.error("Error listening to port" + port, t);
            listenHandler.handle(Future.<TermServer>failedFuture(t));
        }
        return this;
    }

    @Override
    public int actualPort() {return bootstrap.getPort();
    }

    @Override
    public void close() {close(null);
    }

    @Override
    public void close(Handler<Future<Void>> completionHandler) {if (bootstrap != null) {bootstrap.stop();
            if (completionHandler != null) {completionHandler.handle(Future.<Void>succeededFuture());
            }
        } else {if (completionHandler != null) {completionHandler.handle(Future.<Void>failedFuture("telnet term server not started"));
            }
        }
    }
}

HttpTermServer 继承了 TermServer，其 listen 办法创立 NettyWebsocketTtyBootstrap，而后执行其 start 办法，其 accept 办法执行的是 termHandler.handle(new TermImpl(Helper.loadKeymap(), conn))，最初执行 listenHandler.handle(Future.<TermServer>succeededFuture())；其 close 办法执行的是 bootstrap.stop()

com/taobao/arthas/core/shell/handlers/Handler.java

public interface Handler<E> {
    /**
     * Something has happened, so handle it.
     *
     * @param event the event to handle
     */
    void handle(E event);
}

Handler 定义了 handle 办法

com/taobao/arthas/core/shell/handlers/server/TermServerTermHandler.java

public class TermServerTermHandler implements Handler<Term> {
    private ShellServerImpl shellServer;

    public TermServerTermHandler(ShellServerImpl shellServer) {this.shellServer = shellServer;}

    @Override
    public void handle(Term term) {shellServer.handleTerm(term);
    }
}

TermServerTermHandler 实现了 Handler 接口，其 handle 办法执行的是 shellServer.handleTerm(term)

com/taobao/arthas/core/shell/impl/ShellServerImpl.java

    public void handleTerm(Term term) {synchronized (this) {
            // That might happen with multiple ser
            if (closed) {term.close();
                return;
            }
        }

        ShellImpl session = createShell(term);
        tryUpdateWelcomeMessage();
        session.setWelcome(welcomeMessage);
        session.closedFuture.setHandler(new SessionClosedHandler(this, session));
        session.init();
        sessions.put(session.id, session); // Put after init so the close handler on the connection is set
        session.readline(); // Now readline}

ShellServerImpl 的 handleTerm 办法创立 ShellImpl，而后执行 init，最初执行 readline

com/taobao/arthas/core/shell/impl/ShellImpl.java

    public void readline() {term.readline(prompt, new ShellLineHandler(this),
                new CommandManagerCompletionHandler(commandManager));
    }

ShellImpl 的 readline 委托给了 Term，传入 ShellLineHandler

com/taobao/arthas/core/shell/handlers/shell/ShellLineHandler.java

    public void handle(String line) {if (line == null) {
            // EOF
            handleExit();
            return;
        }

        List<CliToken> tokens = CliTokens.tokenize(line);
        CliToken first = TokenUtils.findFirstTextToken(tokens);
        if (first == null) {
            // For now do like this
            shell.readline();
            return;
        }

        String name = first.value();
        if (name.equals("exit") || name.equals("logout") || name.equals("q") || name.equals("quit")) {handleExit();
            return;
        } else if (name.equals("jobs")) {handleJobs();
            return;
        } else if (name.equals("fg")) {handleForeground(tokens);
            return;
        } else if (name.equals("bg")) {handleBackground(tokens);
            return;
        } else if (name.equals("kill")) {handleKill(tokens);
            return;
        }

        Job job = createJob(tokens);
        if (job != null) {job.run();
        }
    }

ShellLineHandler 的 handle 办法才是真正解决命令的中央，它反对了 exit、logout、q、quit、jobs、fg、bg、kill 命令

HttpTermServer 继承了 TermServer，其 listen 办法创立 NettyWebsocketTtyBootstrap，而后执行其 start 办法，其 accept 办法执行的是 termHandler.handle(new TermImpl(Helper.loadKeymap(), conn))，最初执行 listenHandler.handle(Future.<TermServer>succeededFuture())；其 close 办法执行的是 bootstrap.stop()。

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