SOFABolt 的停机机制分为服务端 RpcServer 停机 和客户端 RpcClient 停机。

• RpcServer 停机步骤

1. 关闭 netty 服务端 boss channel
2. 关闭 bossGroup，workerGroup 不能关掉（因为 workerGroup 是多个 RpcServer 共享的）
3. 如果服务端连接管理器是开启的，遍历所有的连接池 ConnectionPool，关闭池内的所有 Connection（进而关闭 Connection 内部的 netty 服务端 worker channel）

• RpcClient 停机步骤

1. 遍历所有的连接池 ConnectionPool，关闭池内的所有 Connection（进而关闭 Connection 内部的 netty 服务端 worker channel）
2. 关闭 Scannable 任务扫描线程
3. 关闭重连线程 + 清空重连任务
4. 取消连接监听器内的任务 + 销毁连接监听器的线程池

服务端停机 RpcServer

======================================= AbstractRemotingServer =======================================
    public boolean stop() {
        if (started.compareAndSet(true, false)) {
            return this.doStop();
        } else {
            throw new IllegalStateException("ERROR: The server has already stopped!");
        }
    }

======================================= RpcServer =======================================
    protected boolean doStop() {
        // 1. 关闭 netty 服务端 boss channel
        if (null != this.channelFuture) {
            this.channelFuture.channel().close();
        }
        // 2. 关闭 bossGroup，workerGroup 不能关掉（因为是共享的）
        if (this.switches().isOn(GlobalSwitch.SERVER_SYNC_STOP)) {
            this.bossGroup.shutdownGracefully().awaitUninterruptibly();
        } else {
            this.bossGroup.shutdownGracefully();
        }
        // 3. 如果服务端连接管理器是开启的，遍历所有的连接池 ConnectionPool，关闭连接（内部关闭 netty 服务端 worker channel）
        if (this.switches().isOn(GlobalSwitch.SERVER_MANAGE_CONNECTION_SWITCH) && null != this.connectionManager) {
            this.connectionManager.removeAll();
        }
        return true;
    }

======================================= DefaultConnectionManager =======================================
    // connection pool initialize tasks
    protected ConcurrentHashMap<String, RunStateRecordedFutureTask<ConnectionPool>> connTasks;

    public void removeAll() {
        if (null == this.connTasks || this.connTasks.isEmpty()) {
            return;
        }
        if (null != this.connTasks && !this.connTasks.isEmpty()) {
            Iterator<String> iter = this.connTasks.keySet().iterator();
            // 遍历所有的连接池 ConnectionPool，关闭所有 Connection（包括 Connection 内的 netty worker channel）
            while (iter.hasNext()) {
                String poolKey = iter.next();
                this.removeTask(poolKey);
                iter.remove();
            }
        }
    }

    private void removeTask(String poolKey) {
        RunStateRecordedFutureTask<ConnectionPool> task = this.connTasks.remove(poolKey);
        if (null != task) {
            ConnectionPool pool = FutureTaskUtil.getFutureTaskResult(task, logger);
            if (null != pool) {
                pool.removeAllAndTryClose();
            }
        }
    }

======================================= ConnectionPool =======================================
    // remove all connections
    public void removeAllAndTryClose() {
        for (Connection conn : this.conns) {
            removeAndTryClose(conn);
        }
        this.conns.clear();
    }

    public void removeAndTryClose(Connection connection) {
        if (null == connection) {
            return;
        }
        boolean res = this.conns.remove(connection);
        if (res) {
            connection.decreaseRef();
        }
        if (connection.noRef()) {
            connection.close();
        }
    }

======================================= Connection =======================================
    // Close the connection.
    public void close() {
        if (closed.compareAndSet(false, true)) {
            if (this.getChannel() != null) {
                this.getChannel().close();
            }
        }
    }

客户端停机 RpcClient

======================================= RpcClient =======================================
    public void shutdown() {
        // 1. 遍历所有的连接池 ConnectionPool，关闭池内的所有 Connection（进而关闭 Connection 内部的 netty 服务端 worker channel）
        // 这一步与服务端开启了连接管理一样，不再赘述
        this.connectionManager.removeAll();
        // 2. 关闭 Scannable 任务扫描线程
        this.taskScanner.shutdown();
        // 3. 关闭重连线程 + 清空重连任务
        if (reconnectManager != null) {
            reconnectManager.stop();
        }
        // 4. 销毁连接监听器的线程池
        if (connectionMonitor != null) {
            connectionMonitor.destroy();
        }
    }

======================================= RpcTaskScanner =======================================
    private ScheduledExecutorService scheduledService = new ScheduledThreadPoolExecutor(1,new NamedThreadFactory("RpcTaskScannerThread", true));

    // Shutdown the scheduled service.
    public void shutdown() {
        scheduledService.shutdown();
    }

======================================= ReconnectManager =======================================
    private final Thread healConnectionThreads; // 重连线程
    // stop reconnect thread
    public void stop() {
        if (!this.started) {
            return;
        }
        this.started = false;
        healConnectionThreads.interrupt();
        this.tasks.clear();
        this.canceled.clear();
    }

======================================= DefaultConnectionMonitor =======================================
    private ScheduledThreadPoolExecutor executor;
    // cancel task and shutdown executor
    public void destroy() {
        // Tries to remove from the work queue all Future tasks that have been cancelled
        executor.purge();
        executor.shutdown();
    }