系列文章
前言
前几篇文章分别从使用和源码层面对Quartz做了简单的分析，在分析的过程中也发现了Quartz不足的地方；比如底层调度依赖数据库的悲观锁，谁先抢到谁调度，这样会导致节点负载不均衡；还有调度和执行耦合在一起，导致调度器会受到业务的影响；下面看看如何来解决这几个问题；
思路
调度器和执行器拆成不同的进程，调度器还是依赖Quartz本身的调度方式，但是调度的并不是具体业务的QuartzJobBean，而是统一的一个RemoteQuartzJobBean，在此Bean中通过Netty远程调用执行器去执行具体业务Bean；具体的执行器在启动时注册到Zookeeper中，调度器可以在Zookeeper获取执行器信息，并通过相关的负载算法指定具体的执行器去执行，以下看简单的实现；
执行器
1.执行器配置文件
executor_name=firstExecutorservice_address=127.0.0.1:8000registry_address=127.0.0.1:2181
配置了执行器的名称，执行器启动的ip和端口以及Zookeeper的地址信息；
2.执行器服务
ExecutorServer通过Netty启动服务，并向Zookeeper注册服务，部分代码如下：
EventLoopGroup bossGroup = new NioEventLoopGroup();EventLoopGroup workerGroup = new NioEventLoopGroup();try { // 创建并初始化 Netty 服务端 Bootstrap 对象 ServerBootstrap bootstrap = new ServerBootstrap(); bootstrap.group(bossGroup, workerGroup); bootstrap.channel(NioServerSocketChannel.class); bootstrap.childHandler(new ChannelInitializer () { @Override public void initChannel(SocketChannel channel) throws Exception { ChannelPipeline pipeline = channel.pipeline(); pipeline.addLast(new RpcDecoder(Request.class)); pipeline.addLast(new RpcEncoder(Response.class)); pipeline.addLast(new ExecutorServerHandler(handlerMap)); } }); bootstrap.option(ChannelOption.SO_BACKLOG, 1024); bootstrap.childOption(ChannelOption.SO_KEEPALIVE, true); // 获取 RPC 服务器的 IP 地址与端口号 String[] addressArray = StringUtils.splitByWholeSeparator(serviceAddress, ":"); String ip = addressArray[0]; int port = Integer.parseInt(addressArray[1]); // 启动 RPC 服务器 ChannelFuture future = bootstrap.bind(ip, port).sync(); // 注册 RPC 服务地址 if (serviceRegistry != null) { serviceRegistry.register(executorName, serviceAddress); LOGGER.info("register service: {} => {}", executorName, serviceAddress); } LOGGER.info("server started on port {}", port); // 关闭 RPC 服务器 future.channel().closeFuture().sync();} finally { workerGroup.shutdownGracefully(); bossGroup.shutdownGracefully();} 在Netty中指定了编码器解码器，同时指定了ExecutorServerHandler用来处理调度器发送来的消息（更多代码查看项目源码）；最后向Zookeeper注册服务，路径格式如下：
/job_registry/firstExecutor/address-0000000008
job_registry是固定值，firstExecutor是配置的具体执行器名称；
3.配置加载任务
添加注解类，用来指定具体的业务Job：
@Target({ ElementType.TYPE })@Retention(RetentionPolicy.RUNTIME)@Componentpublic @interface ExecutorTask { String name(); } 例如具体的业务Task如下所示：
@ExecutorTask(name = "firstTask")public class FirstTask implements IJobHandler { private static final Logger LOGGER = LoggerFactory.getLogger(FirstTask.class); @Override public Result execute(String param) throws Exception { LOGGER.info("execute firstTask"); return SUCCESS; } } 在启动执行器服务时，加载有ExecutorTask注解的任务类，此处定义的name要和调度端的名称相互匹配；
4.执行具体业务
Netty中指定了ExecutorServerHandler用来处理接受的调度器信息，通过反射的方式来调用具体的业务Job，部分代码如下：
private Object handle(Request request) throws Exception { // 获取服务对象 String serviceName = request.getInterfaceName(); Object serviceBean = handlerMap.get(serviceName); if (serviceBean == null) { throw new RuntimeException(String.format("can not find service bean by key: %s", serviceName)); } // 获取反射调用所需的参数 Class serviceClass = serviceBean.getClass(); String methodName = request.getMethodName(); Class [] parameterTypes = request.getParameterTypes(); Object[] parameters = request.getParameters(); // 使用 CGLib 执行反射调用 FastClass serviceFastClass = FastClass.create(serviceClass); FastMethod serviceFastMethod = serviceFastClass.getMethod(methodName, parameterTypes); return serviceFastMethod.invoke(serviceBean, parameters); } serviceName对应的就是定义的”firstTask”，然后通过serviceName找到对应的Bean，然后反射调用，最终返回结果；
调度器
调度器还是依赖Quartz的原生调度方式，只不过调度器不在执行相关业务Task，所以相关配置也是类似，同样依赖数据库；
1.定义调度任务
同样在调度端定义了名称问firstTask的任务，可以发现此类是RemoteQuartzJobBean，并不是具体的业务Task；同时也指定了jobDataMap，用来指定执行器名称和发现的Zookeeper地址；
2.RemoteQuartzJobBean
public class RemoteQuartzJobBean extends QuartzJobBean { private static final Logger LOGGER = LoggerFactory.getLogger(RemoteQuartzJobBean.class); private ExecutorBean executorBean; @Override protected void executeInternal(JobExecutionContext context) throws JobExecutionException { JobKey jobKey = context.getTrigger().getJobKey(); LOGGER.info("jobName:" + jobKey.getName() + ",group:" + jobKey.getGroup()); IJobHandler executor = JobProxy.create(IJobHandler.class, jobKey, this.executorBean); Result result; try { result = executor.execute(""); LOGGER.info("result:" + result); } catch (Exception e) { LOGGER.error("", e); } } public ExecutorBean getExecutorBean() { return executorBean; } public void setExecutorBean(ExecutorBean executorBean) { this.executorBean = executorBean; } } 此类同样继承于QuartzJobBean，这样Quartz才能调度Bean，在此Bean中通过jobKey和executorBean创建了IJobHandler的代理类，具体代码如下：
public staticT create(final Class interfaceClass, final JobKey jobKey, final ExecutorBean executor) { // 创建动态代理对象 return (T) Proxy.newProxyInstance(interfaceClass.getClassLoader(), new Class [] { interfaceClass }, new InvocationHandler() { @Override public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { // 创建 RPC 请求对象并设置请求属性 Request request = new Request(); request.setRequestId(UUID.randomUUID().toString()); request.setInterfaceName(jobKey.getName()); request.setMethodName(method.getName()); request.setParameterTypes(method.getParameterTypes()); request.setParameters(args); String serviceAddress = null; ServiceDiscovery serviceDiscovery = ServiceDiscoveryFactory .getServiceDiscovery(executor.getDiscoveryAddress()); // 获取 RPC 服务地址 if (serviceDiscovery != null) { serviceAddress = serviceDiscovery.discover(executor.getExecutorName()); LOGGER.debug("discover service: {} => {}", executor.getExecutorName(), serviceAddress); } if (StringUtil.isEmpty(serviceAddress)) { throw new RuntimeException("server address is empty"); } // 从 RPC 服务地址中解析主机名与端口号 String[] array = StringUtil.split(serviceAddress, ":"); String host = array[0]; int port = Integer.parseInt(array[1]); // 创建 RPC 客户端对象并发送 RPC 请求 ExecutorClient client = new ExecutorClient(host, port); long time = System.currentTimeMillis(); Response response = client.send(request); LOGGER.debug("time: {}ms", System.currentTimeMillis() - time); if (response == null) { throw new RuntimeException("response is null"); } // 返回 RPC 响应结果 if (response.hasException()) { throw response.getException(); } else { return response.getResult(); } } }); }
在Request中指定了InterfaceName为jobKey.getName()，也就是这里的firstTask；通过Zookeeper发现服务时指定了executor.getExecutorName()，这样可以在Zookeeper中找到具体的执行器地址，当然这里的地址可能是一个列表，可以通过负载均衡算法(随机，轮询，一致性hash等等)进行分配，获取到地址后通过Netty远程连接执行器，发送执行job等待返回结果；
简单测试
分别执行调度器和执行器，相关日志如下：
1.执行器日志
2018-09-03 11:17:02 [main] 13::: DEBUG com.zh.job.sample.executor.ExecutorBootstrap - start server2018-09-03 11:17:03 [main] 31::: DEBUG com.zh.job.registry.impl.ZookeeperServiceRegistry - connect zookeeper2018-09-03 11:17:03 [main] 49::: DEBUG com.zh.job.registry.impl.ZookeeperServiceRegistry - create address node: /job_registry/firstExecutor/address-00000000092018-09-03 11:17:03 [main] 107::: INFO com.zh.job.executor.ExecutorServer - register service: firstExecutor => 127.0.0.1:80002018-09-03 11:17:03 [main] 109::: INFO com.zh.job.executor.ExecutorServer - server started on port 80002018-09-03 11:17:15 [nioEventLoopGroup-3-1] 17::: INFO com.zh.job.sample.executor.task.FirstTask - execute firstTask
2.调度器日志
2018-09-03 11:17:14 [myScheduler_Worker-1] 28::: INFO com.zh.job.scheduler.RemoteQuartzJobBean - jobName:firstTask,group:DEFAULT2018-09-03 11:17:15 [myScheduler_Worker-2] 28::: INFO com.zh.job.scheduler.RemoteQuartzJobBean - jobName:firstTask,group:DEFAULT2018-09-03 11:17:15 [myScheduler_Worker-1] 33::: DEBUG com.zh.job.registry.impl.ZookeeperServiceDiscovery - connect zookeeper2018-09-03 11:17:15 [myScheduler_Worker-2] 54::: DEBUG com.zh.job.registry.impl.ZookeeperServiceDiscovery - get only address node: address-00000000092018-09-03 11:17:15 [myScheduler_Worker-1] 54::: DEBUG com.zh.job.registry.impl.ZookeeperServiceDiscovery - get only address node: address-00000000092018-09-03 11:17:15 [myScheduler_Worker-2] 42::: DEBUG com.zh.job.scheduler.JobProxy$1 - discover service: firstExecutor => 127.0.0.1:80002018-09-03 11:17:15 [myScheduler_Worker-1] 42::: DEBUG com.zh.job.scheduler.JobProxy$1 - discover service: firstExecutor => 127.0.0.1:80002018-09-03 11:17:15 [myScheduler_Worker-1] 55::: DEBUG com.zh.job.scheduler.JobProxy$1 - time: 369ms2018-09-03 11:17:15 [myScheduler_Worker-1] 33::: INFO com.zh.job.scheduler.RemoteQuartzJobBean - result:com.zh.job.common.bean.Result@33b61489
总结
本文通过一个实例来分析如何解决原生Quartz调度存在不足的问题，主要体现在调度器与执行器的隔离上，各司其责发挥各自的优势；