Question

I have a thread running under tomcat which creates a HttpUrlConnection and reads it through BufferedInputStream.

After fetching data for some urls, it stalls. I got the jstack of the process which says HttpUrlConnection is locked and BufferedInputStream is also locked.

"http-8080-1" daemon prio=10 tid=0x08683400 nid=0x79c9 runnable [0x8f618000]
   java.lang.Thread.State: RUNNABLE
        at java.net.SocketInputStream.socketRead0(Native Method)
        at java.net.SocketInputStream.read(SocketInputStream.java:129)
        at java.io.BufferedInputStream.fill(BufferedInputStream.java:218)
        at java.io.BufferedInputStream.read1(BufferedInputStream.java:258)
        at java.io.BufferedInputStream.read(BufferedInputStream.java:317)
        - locked <0x956ef8c0> (a java.io.BufferedInputStream)
        at sun.net.www.http.HttpClient.parseHTTPHeader(HttpClient.java:687)
        at sun.net.www.http.HttpClient.parseHTTP(HttpClient.java:632)
        at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1072)
        - locked <0x956ef910> (a sun.net.www.protocol.http.HttpURLConnection)

Could somebody help here.
Thanks

Answer 1

You probably have a problem on the other end. read() on an InputStream is a blocking operation – from the javadoc (http://java.sun.com/javase/6/docs/api/): “This method blocks until input data is available, the end of the stream is detected, or an exception is thrown.”

Is the server on the other end responding? Do you know if it’s sent anything?

edit: To make it clearer, the thread is in RUNNABLE state, so you’re not deadlocked – it sounds like that’s what you’re thinking that it is, but there’s no evidence here of any deadlock.