[GitHub] [dubbo] robberphex commented on issue #10768: Dubbo support project loom

[GitBox <gi...@apache.org>]

robberphex commented on issue #10768:
URL: https://github.com/apache/dubbo/issues/10768#issuecomment-1345461741

   随着JDK 19和 [JEP 425](https://openjdk.org/jeps/425)的发布，是时候调研下dubbo如何支持project loom了。
   
   loom对于上层的要求和建议，主要有几点（难度由低到高）：
   1. 不应该缓存虚拟线程，即不应该像原来使用线程池那样池化。当然，这儿为了兼容性，可以使用`ThreadPerTaskExecutor`
   2. 目前synchronized和native method，会导致虚拟线程无法卸载（即完全占用了一个物理线程）。
       * 预计在将来的版本中，synchronized的限制可以取消，但是native method这一块，需要loom提供新的接口，然后现有的native代码做适配。
       * 我看了目前DubboServerHandler的调用栈，目前是没有上述两种情况的。
   3. loom最终的目标是"Code like sync, works like async"，而dubbo内核依赖了netty这样的，基于回调的编程范式。不论是基于老版本dubbo兼容性考虑，还是基于老版本java兼容性考虑，都没法做大的修改。
   
   **所以，这一块，我们至少可以分2步走**：
   第一步，在现有的基础上，逐步通过VirtualThread替换掉原有的Thread（DubboServerHandler、NettyServerWorker），并观察性能、异步编程难易度。在这一步，我们期望Dubbo的性能会有略微提升，用户的编程难度下降（尤其是流式、异步模式）。
   第二步，根据第一步结果，如果大家都接受"Code like sync, works like async"，那么我们可以逐步改造dubo内核，实现更加容易的异步、高性能编程。
   
   ---
   
   目前进展，在本地跑了简单Demo，需要做出如下改造，即可体验VirtualThread：
   1. 添加`VirtualThreadPool`,
   ```java
   import org.apache.dubbo.common.URL;
   import org.apache.dubbo.common.threadpool.ThreadPool;
   import java.util.concurrent.Executor;
   import java.util.concurrent.Executors;
   import java.util.concurrent.ThreadFactory;
   import static org.apache.dubbo.common.constants.CommonConstants.DEFAULT_THREAD_NAME;
   import static org.apache.dubbo.common.constants.CommonConstants.THREAD_NAME_KEY;
   
   public class VirtualThreadPool implements ThreadPool {
     @Override
     public Executor getExecutor(URL url) {
       String name = url.getParameter(THREAD_NAME_KEY, 
         (String) url.getAttribute(THREAD_NAME_KEY, DEFAULT_THREAD_NAME)
       );
       ThreadFactory factory = Thread.ofVirtual().name(name).factory();
       return Executors.newThreadPerTaskExecutor(factory);
     }
   }
   ```
   2. 添加SPI `src/main/resources/META-INF/dubbo/internal/org.apache.dubbo.common.threadpool.ThreadPool`
   ```
   virtual-thread=VirtualThreadPool
   ```
   3. 使用SPI，添加配置：`dubbo.provider.parameters.threadpool=virtual-thread`
   
   最终的stack：
   ```
   at com.alibaba.edas.boot.EchoServiceImpl.echo(EchoServiceImpl.java:16)
   	at com.alibaba.edas.boot.EchoServiceImplDubboWrap0.invokeMethod(EchoServiceImplDubboWrap0.java)
   	at org.apache.dubbo.rpc.proxy.javassist.JavassistProxyFactory$1.doInvoke(JavassistProxyFactory.java:73)
   	at org.apache.dubbo.rpc.proxy.AbstractProxyInvoker.invoke(AbstractProxyInvoker.java:100)
   	at org.apache.dubbo.config.invoker.DelegateProviderMetaDataInvoker.invoke(DelegateProviderMetaDataInvoker.java:55)
   	at org.apache.dubbo.rpc.protocol.InvokerWrapper.invoke(InvokerWrapper.java:56)
   	at org.apache.dubbo.rpc.filter.ClassLoaderCallbackFilter.invoke(ClassLoaderCallbackFilter.java:38)
   	at org.apache.dubbo.rpc.cluster.filter.FilterChainBuilder$CopyOfFilterChainNode.invoke(FilterChainBuilder.java:327)
   	at org.apache.dubbo.rpc.protocol.dubbo.filter.TraceFilter.invoke(TraceFilter.java:79)
   	at org.apache.dubbo.rpc.cluster.filter.FilterChainBuilder$CopyOfFilterChainNode.invoke(FilterChainBuilder.java:327)
   	at org.apache.dubbo.rpc.filter.TimeoutFilter.invoke(TimeoutFilter.java:45)
   	at org.apache.dubbo.rpc.cluster.filter.FilterChainBuilder$CopyOfFilterChainNode.invoke(FilterChainBuilder.java:327)
   	at org.apache.dubbo.monitor.support.MonitorFilter.invoke(MonitorFilter.java:100)
   	at org.apache.dubbo.rpc.cluster.filter.FilterChainBuilder$CopyOfFilterChainNode.invoke(FilterChainBuilder.java:327)
   	at org.apache.dubbo.rpc.filter.ExceptionFilter.invoke(ExceptionFilter.java:54)
   	at org.apache.dubbo.rpc.cluster.filter.FilterChainBuilder$CopyOfFilterChainNode.invoke(FilterChainBuilder.java:327)
   	at org.apache.dubbo.rpc.filter.GenericFilter.invoke(GenericFilter.java:192)
   	at org.apache.dubbo.rpc.cluster.filter.FilterChainBuilder$CopyOfFilterChainNode.invoke(FilterChainBuilder.java:327)
   	at org.apache.dubbo.rpc.filter.ClassLoaderFilter.invoke(ClassLoaderFilter.java:54)
   	at org.apache.dubbo.rpc.cluster.filter.FilterChainBuilder$CopyOfFilterChainNode.invoke(FilterChainBuilder.java:327)
   	at org.apache.dubbo.rpc.filter.EchoFilter.invoke(EchoFilter.java:41)
   	at org.apache.dubbo.rpc.cluster.filter.FilterChainBuilder$CopyOfFilterChainNode.invoke(FilterChainBuilder.java:327)
   	at org.apache.dubbo.rpc.filter.ProfilerServerFilter.invoke(ProfilerServerFilter.java:57)
   	at org.apache.dubbo.rpc.cluster.filter.FilterChainBuilder$CopyOfFilterChainNode.invoke(FilterChainBuilder.java:327)
   	at org.apache.dubbo.rpc.filter.ContextFilter.invoke(ContextFilter.java:133)
   	at org.apache.dubbo.rpc.cluster.filter.FilterChainBuilder$CopyOfFilterChainNode.invoke(FilterChainBuilder.java:327)
   	at org.apache.dubbo.rpc.cluster.filter.FilterChainBuilder$CallbackRegistrationInvoker.invoke(FilterChainBuilder.java:194)
   	at org.apache.dubbo.rpc.protocol.dubbo.DubboProtocol$1.reply(DubboProtocol.java:156)
   	at org.apache.dubbo.remoting.exchange.support.header.HeaderExchangeHandler.handleRequest(HeaderExchangeHandler.java:102)
   	at org.apache.dubbo.remoting.exchange.support.header.HeaderExchangeHandler.received(HeaderExchangeHandler.java:177)
   	at org.apache.dubbo.remoting.transport.DecodeHandler.received(DecodeHandler.java:53)
   	at org.apache.dubbo.remoting.transport.dispatcher.ChannelEventRunnable.run(ChannelEventRunnable.java:61)
   	at java.base/java.util.concurrent.ThreadPerTaskExecutor$TaskRunner.run(ThreadPerTaskExecutor.java:314)
   	at java.base/java.lang.VirtualThread.run(VirtualThread.java:287)
   	at java.base/java.lang.VirtualThread$VThreadContinuation.lambda$new$0(VirtualThread.java:174)
   	at java.base/jdk.internal.vm.Continuation.enter0(Continuation.java:327)
   	at java.base/jdk.internal.vm.Continuation.enter(Continuation.java:320)
   ```


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