This weekend, I installed NetBeans 8.0.2 and was dismayed that it consistently) took 1' 23" to start. Here’s how I found out what went wrong. Spoiler: it’s a DNS problem.

This post was first published on Medium, but I moved it over here.

I tweeted about my predicament:

The splash screen is shown and sits there, no notification that anything is wrong, no error message.

I immediately got a few reactions, a.o. from @GeertjanW (Oracle product manager on the NetBeans team) who was kind enough to offer his help figuring out what was going on.

He made a few suggestions, a.o. printing out a thread dump during startup. This revealed some interesting results:

[...]
"AWT-EventQueue-0" #20 prio=6 os_prio=0 tid=0x00007f3728102800 nid=0x19f3 waiting for monitor entry [0x00007f377fbf9000]
   java.lang.Thread.State: BLOCKED (on object monitor)
       at java.net.InetAddress.getLocalHost(InetAddress.java:1465)
       - waiting to lock <0x00000000c080a788> (a java.lang.Object)
       at sun.font.FcFontConfiguration.getFcInfoFile(FcFontConfiguration.java:352)
       at sun.font.FcFontConfiguration.readFcInfo(FcFontConfiguration.java:425)
       at sun.font.FcFontConfiguration.init(FcFontConfiguration.java:94)
[...]
"main" #15 prio=5 os_prio=0 tid=0x00007f37a4612000 nid=0x19ee waiting for monitor entry [0x00007f3784dce000]
   java.lang.Thread.State: BLOCKED (on object monitor)
       at java.net.InetAddress.getLocalHost(InetAddress.java:1465)
       - waiting to lock <0x00000000c080a788> (a java.lang.Object)
       at org.eclipse.osgi.framework.internal.core.UniversalUniqueIdentifier.getIPAddress(UniversalUniqueIdentifier.java:146)
       at org.eclipse.osgi.framework.internal.core.UniversalUniqueIdentifier.computeNodeAddress(UniversalUniqueIdentifier.java:113)
       at org.eclipse.osgi.framework.internal.core.UniversalUniqueIdentifier.<clinit>(UniversalUniqueIdentifier.java:35)
[...]

Basically, it appears the method getLocalHost() was slowing everything down. I fired up Wireshark to see if some network traffic was generated. Indeed, I saw eight DNS lookups on my laptop’s host name (four A and four AAAA lookups).

Of course, this does not resolve. On my home network, my router is the DNS server and only replies after about fifteen seconds if a host name is not found. The getLocalHost() method, when it doesn’t receive a response within five seconds, will repeat the request a few times. In total, the method, tested with the following Java program, takes twenty seconds when DNS requests time out…

TestLocalHost.javaTestLocalHost.java 
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public class TestLocalHost {
  public static void main(String[] args) throws Exception {
    System.out.println(java.net.InetAddress.getLocalHost());
  }
}

At work, the DNS server immediately replies when a hostname does not resolve, so the startup time of NetBeans is considerably faster (about three seconds).

So, apparently, getLocalHost() is called a few (four?) times during startup, resulting in 1' 23" total…

The solution/workaround is to add an entry for my hostname to /etc/hosts.

And @KrisBuytaert is right once again…