1. 技术文章
  2. Commons Net FTPClient hangs indefinitely with Mule

Commons Net FTPClient hangs indefinitely with Mule

由 末鹿安然 提交于 2019-12-06 06:23:53

In an ideal world the timeout should not be necessary, but it looks like in your case it is.

Your description is very comprehensive, have you considered to raise a bug?

To workaround I would suggest first to use "Response Timeout" in the advanced tab. If that doesnt work I would use a service override, from there you should be able to override the receiver.

I reproduced the error in both my previous cases using MockFtpServer, and I was able to use a FtpConnectionFactory which seems to solve the issue.

public class SafeFtpConnectionFactory extends FtpConnectionFactory{

    //define a default timeout
    public static int defaultTimeout = 60000;
    public static synchronized int getDefaultTimeout() {
        return defaultTimeout;
    }
    public static synchronized void setDefaultTimeout(int defaultTimeout) {
        SafeFtpConnectionFactory.defaultTimeout = defaultTimeout;
    }

    public SafeFtpConnectionFactory(EndpointURI uri) {
        super(uri);
    }

    @Override
    protected FTPClient createFtpClient() {
        FTPClient client = super.createFtpClient();

        //Define the default timeout here, which will be used by the socket by default,
        //instead of the 0 timeout hanging indefinitely
        client.setDefaultTimeout(getDefaultTimeout());

        return client;
    }
}

And then attaching it to my connector:

<ftp:connector name="archivingFtpConnector" doc:name="FTP"
        pollingFrequency="${frequency}"
        validateConnections="true"
        connectionFactoryClass="my.comp.SafeFtpConnectionFactory">
    <reconnect frequency="${reconnection.frequency}" count="${reconnection.attempt}"/>
</ftp:connector>

Using this configuration, a java.net.SocketTimeoutException will be thrown after the specified timeout, such as:

java.net.SocketTimeoutException: Read timed out
    at java.net.SocketInputStream.socketRead0(Native Method)
    at java.net.SocketInputStream.read(SocketInputStream.java:152)
    at java.net.SocketInputStream.read(SocketInputStream.java:122)
    at sun.nio.cs.StreamDecoder.readBytes(StreamDecoder.java:283)
    at sun.nio.cs.StreamDecoder.implRead(StreamDecoder.java:325)
    at sun.nio.cs.StreamDecoder.read(StreamDecoder.java:177)
    at java.io.InputStreamReader.read(InputStreamReader.java:184)
    at java.io.BufferedReader.fill(BufferedReader.java:154)
    at java.io.BufferedReader.readLine(BufferedReader.java:317)
    at java.io.BufferedReader.readLine(BufferedReader.java:382)
    at org.apache.commons.net.ftp.FTP.__getReply(FTP.java:294)
    at org.apache.commons.net.ftp.FTP._connectAction_(FTP.java:364)
    at org.apache.commons.net.ftp.FTPClient._connectAction_(FTPClient.java:540)
    at org.apache.commons.net.SocketClient.connect(SocketClient.java:178)
    at org.mule.transport.ftp.FtpConnectionFactory.makeObject(FtpConnectionFactory.java:33)
    at org.apache.commons.pool.impl.GenericObjectPool.borrowObject(GenericObjectPool.java:1188)
    at org.mule.transport.ftp.FtpConnector.getFtp(FtpConnector.java:172)
    at org.mule.transport.ftp.FtpConnector.createFtpClient(FtpConnector.java:637)
    ...

Otherwise, an attempt at connect() or pasv() would hang indefinitely without server response. I reproduced this exact behavior using mock FTP.

Note: I used setDefaultTimeout() as it seems to be the variable used with connect() and connectAction() (from SocketClient source):

public abstract class SocketClient
{
    ...
    protected void _connectAction_() throws IOException
    {
        ...
        _socket_.setSoTimeout(_timeout_);
        ...
    }
    ...
    public void  setDefaultTimeout(int timeout)
    {
        _timeout_ = timeout;
    }
    ...
}

EDIT: For those who are interested, here is the test code for mock FTP used to reproduce the never answering server. The infinite loop is far from good practice though. It should be replaced with something like sleep with an enclosing Test class expecting a SocketTimeout exception and ensuring failure after a given timeout.

    private static final int CONTROL_PORT = 2121;

    public void startStubFtpServer(){
        FakeFtpServer fakeFtpServer = new FakeFtpServer();

        //define the command which should never be answered
        fakeFtpServer.setCommandHandler(CommandNames.PASV, new EverlastingCommandHandler());
        //fakeFtpServer.setCommandHandler(CommandNames.CONNECT, new EverlastingConnectCommandHandler());
        //or any other command...

        //server config
        ...

        //start server
        fakeFtpServer.setServerControlPort(CONTROL_PORT);
        fakeFtpServer.start();

        ...

    }

    //will cause any command received to never have an answer
    public class EverlastingConnectCommandHandler extends org.mockftpserver.core.command.AbstractStaticReplyCommandHandler{
        @Override
        protected void handleCommand(Command cmd, Session session, InvocationRecord rec) throws Exception {
            while(true){
                try {
                    Thread.sleep(60000);
                } catch (InterruptedException e) {
                    //TODO
                }
            }
        }

    }
    public class EverlastingCommandHandler extends AbstractFakeCommandHandler {
        @Override
        protected void handle(Command cmd, Session session) {
            while(true){
                try {
                    Thread.sleep(60000);
                } catch (InterruptedException e) {
                    //TODO
                }
            }
        }
    };
标签
java
sockets
ftp
mule
hang
易学教程内所有资源均来自网络或用户发布的内容，如有违反法律规定的内容欢迎反馈！
该文章没有解决你所遇到的问题?点击提问,说说你的问题,让更多的人一起探讨吧!