Java URLConnection provides no fail-safe timeout on reads

While it does sport a setReadTimeout() call, it does not work if the server returns some data and then gets stuck. There are servers like this in the real world, for example try this:

curl http://www.geo-mobile.com/nuke/index.php

You have to use a separate timer thread to timeout any reads.

                try {
                    URLConnection con = urlObj.openConnection();
                    con.setConnectTimeout(5000);
                    con.setReadTimeout(5000);
                    new Thread(new InterruptThread(Thread.currentThread(), con)).start();
                    retVal = new Source(con);
                } catch (IOException e) {
                    System.err.println("aborted parsing due to I/O: " + e.getMessage());
                    throw new IndexingException("aborted parsing due to timeout - " + aUrl);
                }

In this example, the Source constructor, using the Jericho parser retrieves a web page and it can get stuck on a socket read call. The timeouts don't have any effect. And it is not possible to interrupt a thread waiting on I/O using Thread.interrupt().

The solution is the hand-crafted InterruptThread class:

public class InterruptThread implements Runnable {
    Thread parent;
    URLConnection con;
    public InterruptThread(Thread parent, URLConnection con) {
        this.parent = parent;
        this.con = con;
    }

    public void run() {
        try {
            Thread.sleep(5000);
        } catch (InterruptedException e) {

        }
        System.out.println("Timer thread forcing parent to quit connection");
        ((HttpURLConnection)con).disconnect();
        System.out.println("Timer thread closed connection held by parent, exiting");
    }
}

Here, the InterruptThread forcibly closes the URLConnection held by the parent thread, forcing the Source constructor of the parent thread to throw an IOException, which is handled by its catch block, thus avoiding the hang.