[jira] Updated: (XMLRPC-166) Misbehaving clients can hang ServletWebServer

["Alan Burlison (JIRA)" <xm...@ws.apache.org>]

     [ https://issues.apache.org/jira/browse/XMLRPC-166?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Alan Burlison updated XMLRPC-166:
---------------------------------

    Attachment: hang.patch

Here's what I've done: In the existing code the HttpServletRequestImpl constructor reads the HTTP headers, and if the client doesn't send any headers, the constructor hangs, and that hangs the thread that accepts incoming connections.  I've factored out the header reading code into a new method (readHttpHeaders) which is called from the ServletConnection.run method of the thread that processes the request:

    public void run() throws Throwable {
        try {
            request.readHttpHeaders();
            servlet.service(request, response);
        } catch (Throwable t) {
            if (!shuttingDown) {
                throw t;
            }
        }
    }

>> I also note that Connection class does this:
>>
>>        // set read timeout to 30 seconds
>>        socket.setSoTimeout (30000);
>>
>> That *should* mean that the maximum time a client can hang the server for is
>> 30 seconds, but by observation that's clearly not happening and needs
>> further investigation.
>
> Patches in that area should be welcome as well.

Also fixed.  The problem was that although the Connection class set a 30 second timeout, the ServletConnection didn't - the constructor was missing the call to setSoTimeout.  The Connection class is used by the WebServer class, ServletConnection is used by ServletWebServer.

In combination, these changes mean that a client that doesn't send any headers can't hang the accept() thread, and that after 30 seconds, any such misbehaving client will have its connection terminated.

> Misbehaving clients can hang ServletWebServer
> ---------------------------------------------
>
>                 Key: XMLRPC-166
>                 URL: https://issues.apache.org/jira/browse/XMLRPC-166
>             Project: XML-RPC
>          Issue Type: Bug
>    Affects Versions: 3.1.1
>            Reporter: Alan Burlison
>         Attachments: hang.patch
>
>
> We are using the ServletWebServer class, and we are getting occasional hangs, where the listener thread gets stuck as follows:
> "XML-RPC Weblistener" prio=3 tid=0x089bd000 nid=0x15 runnable [0xe22ce000..0xe22ceb60]
>    java.lang.Thread.State: RUNNABLE
>     at java.net.SocketInputStream.socketRead0(Native Method)
>     at java.net.SocketInputStream.read(SocketInputStream.java:129)
>     at com.sun.net.ssl.internal.ssl.InputRecord.readFully(InputRecord.java:293)
>     at com.sun.net.ssl.internal.ssl.InputRecord.read(InputRecord.java:331)
>     at com.sun.net.ssl.internal.ssl.SSLSocketImpl.readRecord(SSLSocketImpl.java:789)
>     - locked <0xeb722510> (a java.lang.Object)
>     at com.sun.net.ssl.internal.ssl.SSLSocketImpl.readDataRecord(SSLSocketImpl.java:746)
>     at com.sun.net.ssl.internal.ssl.AppInputStream.read(AppInputStream.java:75)
>     - locked <0xeb722838> (a com.sun.net.ssl.internal.ssl.AppInputStream)
>     at java.io.BufferedInputStream.fill(BufferedInputStream.java:218)
>     at java.io.BufferedInputStream.read(BufferedInputStream.java:237)
>     - locked <0xeb72ae70> (a org.apache.xmlrpc.webserver.HttpServletRequestImpl$1)
>     at org.apache.xmlrpc.webserver.HttpServletRequestImpl$2.read(HttpServletRequestImpl.java:94)
>     at javax.servlet.ServletInputStream.readLine(ServletInputStream.java:94)
>     at org.apache.xmlrpc.webserver.HttpServletRequestImpl.readLine(HttpServletRequestImpl.java:170)
>     at org.apache.xmlrpc.webserver.HttpServletRequestImpl. (HttpServletRequestImpl.java:106)
>     at org.apache.xmlrpc.webserver.ServletConnection. (ServletConnection.java:50)
>     at org.apache.xmlrpc.webserver.ServletWebServer.newTask(ServletWebServer.java:145)
>     at org.apache.xmlrpc.webserver.WebServer.run(WebServer.java:335)
>     at java.lang.Thread.run(Thread.java:619)
> The problem is this: when an incoming connection comes in, a new HttpServletRequestImpl object is created.  The constructor of that class reads in the HTTP headers.  The problem with *that* is that the HttpServletRequestImpl constructor runs in the same thread that accepts incoming connections, so if it blocks for any reason (e.g. the client hangs) it blocks the accept thread, which means that any new connections also hang.
> I'm therefore proposing that the reading of the HTTP headers be factored out of the HttpServletRequestImpl constructor and into a new method that is called from the 'run' method of the thread that handles the request.  That way, a client that hangs will only hang the thread that is servicing it and not the entire XML-RPC server.
> Can anyone think of any reasons why this might cause problems?  If not I'll do the changes and submit a patch.
> I also note that Connection class does this:
>         // set read timeout to 30 seconds
>         socket.setSoTimeout (30000);
> That *should* mean that the maximum time a client can hang the server for is 30 seconds, but by observation that's clearly not happening and needs further investigation.

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