Comment 11 for bug 1998311

> It looks like the main thing here is the config for the proxy balancer for the app?

Yes, and specifically enabling the AJP health check (hcmethod=CPING) instead of the usual HTTP/TCP health checks (hcmethod=GET and hcmethod=TCP rispectively)

> I'm also curious about the inclusion of apr from upstream svn (and libaprutil1-dev which is presumably a build dep). Does the issue still crop up even with apr omitted?

Building from upstream svn (both httpd and apr) was just a mean to show apache2 maintainers that the issue can be reproduced with the latest bits; the issue is still present with apr installed from binary packages.

[Test Case]
# apt update && apt dist-upgrade -y
# apt install -y apache2
# cat > /etc/apache2/sites-available/httpd-hcheck-ajp.conf << __EOF__
<VirtualHost *:80>
    ServerAdmin <email address hidden>
    DocumentRoot "/var/www/html"
    ServerName myapp.example.com
    ErrorLog "logs/myapp.example.com-error_log"
    CustomLog "logs/myapp.example.com-access_log" common

    <Proxy balancer://myapp>
        BalancerMember ajp://127.0.0.1:8009/myapp route=app-route timeout=300 ping=3 connectiontimeout=3 hcmethod=CPING
    </Proxy>

    ProxyPass /myapp balancer://myapp stickysession=JSESSIONID

</VirtualHost>
__EOF__
# a2enmod proxy
# a2enmod proxy_ajp
# a2enmod proxy_hcheck
# a2ensite httpd-hcheck-ajp
# apachectl -t

Example failed output:

root@ubuntu:~# apachectl -t
AH00526: Syntax error on line 10 of /etc/apache2/sites-enabled/httpd-hcheck-ajp.conf:
BalancerMember Health check method CPING not (yet) implemented
Action '-t' failed.
The Apache error log may have more information.

Example of successful (expected) output:

root@ubuntu:~# apachectl -t
Syntax OK