Tomcat AJP broken in combination with Apache 2.4

[Thomas]

After upgrading Tomcat 8 to 8.5.30-1ubuntu1, the AJP connector in combination with Apache 2.4 (2.4.29-1ubuntu4) doesn't work any more on Bionic. I guess this is a quite common combination. Of course this could also be caused by Apache, but before the Tomcat upgrade (probably on 8.5.29-1) everything was fine.

My config on Apache side:
    ProxyPass / ajp://localhost:8009/myapp/
    ProxyPassReverse / ajp://localhost:8009/myapp/

My config on Tomcat side (no other connectors active):
    <Connector port="8009" protocol="AJP/1.3" redirectPort="8443" address="127.0.0.1" />

Symptoms:

- On first AJP connection, Tomcat goes to 100% CPU.
- The browser runs into timeout.
- If Tomcat access logging is enabled, localhost_access_log is flooded with '- - [01/Jan/1970:00:59:59 +0100] "-" 400 -' very fast until disk space is used up.

Of course I can give you more information if needed.

[Thomas (lostexception)]

This seems to be related to https://bugs.launchpad.net/ubuntu/+source/tomcat8/+bug/1766882 (sorry if this is the wrong way to link another bug). My problem probably was that I was using OpenJDK 8. If the explanation is correct, dependencies and the init script in the tomcat8 package should be changed.

Workaround:

- Install openjdk-11-jre-headless

- Change init script /etc/init.d/tomcat8:
61c61
< for java_version in 9 8
---
> for java_version in 11 9