OpenJdk initial startup time very slow

Question

I'm running openjdk 11.0.3 on a server. Whenever the server has been rebooted (every night): For the first initial launch of my Application, the users have to wait for 35 Seconds before the Application is even started. (Before the first System.out.println is written from main Method.) (subsequent launches are very fast though) I have tried the following option to debug this:

-Xlog:class+load:file=classload.txt

Here are the most important finds:

... 
[2.284s][info][class,load] jdk.internal.loader.URLClassPath$FileLoader source: jrt:/java.base
[5.032s][info][class,load] sun.security.rsa.RSASignature$SHA1withRSA source: jrt:/java.base
…
[5.051s][info][class,load] java.util.LinkedList$Node source: jrt:/java.base 
[8.121s][info][class,load] pos.LFChangeable source: file:/C:/Users/rho/AppData/Roaming/edapp/pos.jar
…
[8.135s][info][class,load] java.io.FileNotFoundException source: jrt:/java.base
[10.584s][info][class,load] sun.reflect.misc.ReflectUtil source: jrt:/java.base
…
[11.744s][info][class,load] java.security.NoSuchAlgorithmException source: jrt:/java.base
[34.853s][info][class,load] jdk.internal.logger.DefaultLoggerFinder source: jrt:/java.base

Why is it hanging for 23 Seconds between loading java.security.NoSuchAlgorithmException and jdk.internal.logger.DefaultLoggerFinder? And what about the other seconds of slowdowns?

edit: Based on the comments, I will clarify some. This is a windows rdp server. Actually, it is more than one server, but the problem persists on all servers. The Application is a standalone Application. So every morning there are problems as users who log in to start the Application, will try to start it multiple times when "nothing happens". I have now tried restarting one of the servers quite a few times, and this is what I found:

Starting my Application with java11 after reboot takes on average 40 seconds before the first System.out.println. Then it is only 1-2 Seconds before my first JFrame shows. Starting my Application with java8 (sun) after reboots takes on average 16 Seconds before the first System.out.println. But I then get a 25 second delay before my first JFrame shows. Starting my Application with java11 after already started with java8 takes on average 4-6 seconds.

Answer 1

Your application might be suffering from the absence of a “class data-sharing (CDS) archive”. Such an archive allows much faster loading of standard classes and has been generated by default by some installers of previous versions, but OpenJDK 11 does not have an installer.

This is addressed by JEP 341:

Currently, a JDK image includes a default class list, generated at build time, in the lib directory. Users who want to take advantage of CDS, even with just the default class list provided in the JDK, must run java -Xshare:dump as an extra step. This option is documented, but many users are unaware of it.

So while this JEP is about JDK 12 doing the necessary steps automatically, it also mentions the fix for JDK 11: just run java -Xshare:dump on the command line once, to generate the archive.

Note that you can improve the startup time even further by including application classes in the CDS. See also the Class Data Sharing section of the JDK 11 documentation.