Comment 17 for bug 1750356

Bionic verification. Starting with the packages that show the bug:

ubuntu@bionic-apache-1750356:~$ apt-cache policy apache2
apache2:
  Installed: 2.4.29-1ubuntu4.2
  Candidate: 2.4.29-1ubuntu4.2
  Version table:
 *** 2.4.29-1ubuntu4.2 500
        500 http://br.archive.ubuntu.com/ubuntu bionic-updates/main amd64 Packages
        100 /var/lib/dpkg/status

status shows the expected error:
(...)
Aug 28 17:20:37 bionic-apache-1750356 systemd[1]: Starting The Apache HTTP Server...
Aug 28 17:20:37 bionic-apache-1750356 apachectl[2040]: AH00526: Syntax error on line 24 of /etc/apache2/sites-enabled/000-default.conf:
Aug 28 17:20:37 bionic-apache-1750356 apachectl[2040]: BalancerMember worker hostname (xxxxxx-xx-xxxxxxxx-xxxxx-xxxxx.xx-xxxx-x.xxxxx-xxx.xxx.xxxxx.xxxx) too long
Aug 28 17:20:37 bionic-apache-1750356 apachectl[2040]: Action 'start' failed.

Upgrading to the packages in proposed:
ubuntu@bionic-apache-1750356:~$ apt-cache policy apache2
apache2:
  Installed: 2.4.29-1ubuntu4.3
  Candidate: 2.4.29-1ubuntu4.3
  Version table:
 *** 2.4.29-1ubuntu4.3 500
        500 http://br.archive.ubuntu.com/ubuntu bionic-proposed/main amd64 Packages
        100 /var/lib/dpkg/status
     2.4.29-1ubuntu4.2 500
        500 http://br.archive.ubuntu.com/ubuntu bionic-updates/main amd64 Packages

Service is running right after the upgrade:
ubuntu@bionic-apache-1750356:~$ sudo systemctl status apache2
● apache2.service - The Apache HTTP Server
   Loaded: loaded (/lib/systemd/system/apache2.service; enabled; vendor preset: enabled)
  Drop-In: /lib/systemd/system/apache2.service.d
           └─apache2-systemd.conf
   Active: active (running) since Tue 2018-08-28 17:22:31 UTC; 25s ago
 Main PID: 2847 (apache2)
    Tasks: 54 (limit: 4915)
   CGroup: /system.slice/apache2.service
           ├─2847 /usr/sbin/apache2 -k start
           ├─2849 /usr/sbin/apache2 -k start
           └─2850 /usr/sbin/apache2 -k start

Aug 28 17:22:31 bionic-apache-1750356 systemd[1]: Starting The Apache HTTP Server...
Aug 28 17:22:31 bionic-apache-1750356 systemd[1]: Started The Apache HTTP Server.

Accessing the balancer url triggers the expected error:
ubuntu@bionic-apache-1750356:~$ wget http://localhost/foo
--2018-08-28 17:23:34-- http://localhost/foo
Resolving localhost (localhost)... 127.0.0.1
Connecting to localhost (localhost)|127.0.0.1|:80... connected.
HTTP request sent, awaiting response... 502 Proxy Error
2018-08-28 17:23:35 ERROR 502: Proxy Error.

And the logs confirm that the server tried to reach the balancer member:
ubuntu@bionic-apache-1750356:~$ tail /var/log/apache2/error.log -n 1
[Tue Aug 28 17:23:35.277191 2018] [proxy:error] [pid 2850:tid 139871414892288] [client 127.0.0.1:49520] AH00898: DNS lookup failure for: xxxxxx-xx-xxxxxxxx-xxxxx-xxxxx.xx-xxxx-x.xxxxx-xxx.xxx.xxxxx.xxxx returned by /foo

Verification complete and successfull for bionic.