I didn't mix the two options. Because the scenario with thr ruby runner did not work, I've tried to use LSAPI directly. I changed my application accordiing to the documentation. Then I added a external app with my application.rb as command and defined a lsapi context using the ext app. No script handler anymore. But it still doesn't work. The following error messages are shown:
2007-07-15 21:03:24.241 [NOTICE] [127.0.0.1:50619-0#application] Premature end of response header.
2007-07-15 21:03:25.280 [NOTICE] [127.0.0.1:50621-0#application] Premature end of response header.
So what does that mean?