HttpURLConnection timeout seems to be ignored

Question

I'm trying to properly configure the timeouts for my connections using HttpURLConnection.

My problem is that after the getResponseCode() call It always timeouts after 60 seconds instead of the value I set. My code:

    URL url = new URL(uri.toString());
    HttpURLConnection connection = (HttpURLConnection)url.openConnection();
    connection.setConnectTimeout(15000);
    connection.setReadTimeout(15000);
    int responseCode = connection.getResponseCode();

What do I am missing?

Answer 1

I also encountered the same kind of problem a few days back, So did some research.

My problem is that after the getResponseCode() call It always timeouts after 60 seconds instead of the value I set.

this is because InetAddress.getByName(String) does a DNS lookup. That lookup is not part of the connection timeout.

The JDK doesn't let you specify a timeout here. It simply uses the timeouts of the underlying name resolution mechanism.

Anyway, I suspect the effect is not limited to Java. You should be able to observe the same timeouts using nslookup or the host command from a terminal. In a "normal" environment DNS lookup timeouts should be of the order of 1-3 seconds, but not 20 seconds. So I strongly suspect your network setup is broken.

Several things can lead to such insane timeouts:

• DNS server not reachable (UDP port 53), but ICMP is filtered, so the client cannot fail fast
• local firewall on DNS server dropping packets on closed TCP ports instead of sending RST
• intermediate firewalls blocking ICMP messages
• lookups performed over IPv6, but missing IPv6 connectivity
• AAAA record lookups before A record lookup
• your DNS server performs full recursion but no caching. Clients should always query a DNS cache, never a recursor only.

Workaround: You may perform the lookup before sending the request, so the result is already pre-cached.