什么可能导致 RMI 方法调用间歇性失败？

Question

长话短说，我有一个 RMI 服务器和客户端。服务器和客户端能够相互进行 RMI 调用。 Client 连接到 Server 后，Server 可能会在 Client 上连续快速调用数百个方法。

问题是这样的 - 在大量服务器到客户端方法调用结束时，有些会失败，因为 RMI 声称它无法建立从服务器到客户端的连接，即使之前的数百次调用也会成功。我不能发布任何真正的代码，因为这个项目相当大（大约 50k 行），但这里是抛出异常的完整堆栈跟踪：

java.rmi.ServerException: RemoteException occurred in server thread; nested exception is:
java.rmi.ConnectIOException: error during JRMP connection establishment; nested exception is:
java.net.SocketException: Connection reset
at sun.rmi.server.UnicastServerRef.dispatch(Unknown Source)
at sun.rmi.transport.Transport$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at sun.rmi.transport.Transport.serviceCall(Unknown Source)
at sun.rmi.transport.tcp.TCPTransport.handleMessages(Unknown Source)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(Unknown Source)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
at sun.rmi.transport.StreamRemoteCall.exceptionReceivedFromServer(Unknown Source)
at sun.rmi.transport.StreamRemoteCall.executeCall(Unknown Source)
at sun.rmi.server.UnicastRef.invoke(Unknown Source)
at java.rmi.server.RemoteObjectInvocationHandler.invokeRemoteMethod(Unknown Source)
at java.rmi.server.RemoteObjectInvocationHandler.invoke(Unknown Source)
at $Proxy0.findClassDefinition(Unknown Source)
at com.fabric.network.NetworkClassLoader.findClass(NetworkClassLoader.java:111)
at java.lang.ClassLoader.loadClass(Unknown Source)
at com.fabric.network.NetworkClassLoader.loadClass(NetworkClassLoader.java:131)
at java.lang.ClassLoader.loadClass(Unknown Source)
at com.fabric.network.MessageSocket$CustomObjectInputStream.resolveClass(MessageSocket.java:171)
at java.io.ObjectInputStream.readNonProxyDesc(Unknown Source)
at java.io.ObjectInputStream.readClassDesc(Unknown Source)
at java.io.ObjectInputStream.readOrdinaryObject(Unknown Source)
at java.io.ObjectInputStream.readObject0(Unknown Source)
at java.io.ObjectInputStream.defaultReadFields(Unknown Source)
at java.io.ObjectInputStream.readSerialData(Unknown Source)
at java.io.ObjectInputStream.readOrdinaryObject(Unknown Source)
at java.io.ObjectInputStream.readObject0(Unknown Source)
at java.io.ObjectInputStream.defaultReadFields(Unknown Source)
at java.io.ObjectInputStream.readSerialData(Unknown Source)
at java.io.ObjectInputStream.readOrdinaryObject(Unknown Source)
at java.io.ObjectInputStream.readObject0(Unknown Source)
at java.io.ObjectInputStream.readObject(Unknown Source)
at com.fabric.network.MessageSocket.receive(MessageSocket.java:118)
at com.fabric.application.driver.NodeRemoteDriver$IncomingMessageThread.run(NodeRemoteDriver.java:205)
Caused by: java.rmi.ConnectIOException: error during JRMP connection establishment; nested exception is:
java.net.SocketException: Connection reset
at sun.rmi.transport.tcp.TCPChannel.createConnection(Unknown Source)
at sun.rmi.transport.tcp.TCPChannel.newConnection(Unknown Source)
at sun.rmi.server.UnicastRef.invoke(Unknown Source)
at java.rmi.server.RemoteObjectInvocationHandler.invokeRemoteMethod(Unknown Source)
at java.rmi.server.RemoteObjectInvocationHandler.invoke(Unknown Source)
at $Proxy2.findClassDefinition(Unknown Source)
at com.fabric.network.ClassDefinitionCache.findClassDefinition(ClassDefinitionCache.java:78)
at com.fabric.management.host.NodeManagementServices.findClassDefinition(NodeManagementServices.java:231)
at sun.reflect.GeneratedMethodAccessor16.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at sun.rmi.server.UnicastServerRef.dispatch(Unknown Source)
at sun.rmi.transport.Transport$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at sun.rmi.transport.Transport.serviceCall(Unknown Source)
at sun.rmi.transport.tcp.TCPTransport.handleMessages(Unknown Source)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(Unknown Source)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
Caused by: java.net.SocketException: Connection reset
at java.net.SocketInputStream.read(Unknown Source)
at java.io.BufferedInputStream.fill(Unknown Source)
at java.io.BufferedInputStream.read(Unknown Source)
at java.io.DataInputStream.readByte(Unknown Source)
... 21 more

再次抱歉，我无法提供太多代码方面的信息，但我不一定要求修复代码 - 我只是想弄清楚为什么会发生这种情况。

编辑

添加了完整的堆栈跟踪。

Answer 1

好的，所以在几乎把我所有的头发都拉出来之后，事实证明 RMI 试图打开太多的端口。我在后台使用自定义RMISocketFactory 实现。这个自定义实现是单例的，所以我认为没有必要实现hashCode()和equals()。确实是一个非常痛苦的错误……

事实证明，如果 RMI 确定它需要创建的套接字是由 RMISocketFactory 创建的，该 RMISocketFactory 不等同于创建它想要重用的套接字的工厂，那么 RMI 不会重用套接字。 RMI 依赖equals() 和hashCode() 来执行此检查。一旦我在自定义套接字工厂中正确实现了这两种方法，这些间歇性问题就消失了。

这个问题的描述可以在这里找到：

http://docs.oracle.com/javase/7/docs/technotes/guides/rmi/faq.html

无论如何，感谢大家观看本文，非常感谢您抽出宝贵时间！

其他信息

我之前没有注意到的第二个问题是我使用的ServerSocket 的传入连接请求的队列空间不足，这也导致连接被丢弃。使用构造函数new ServerSocket(port, newConnectionQueueSize, bindAddress) 和更大的newConnectionQueueSize 也有助于解决这个问题。