[pkg-uWSGI-devel] Bug#839666: Fails to disable uwsgi module upon purge

Mon Oct 3 16:23:39 UTC 2016

Package: libapache2-mod-uwsgi
Version: 2.0.12-7
Severity: critical
File: /etc/apache2/mods-available/uwsgi.load
Justification: breaks unrelated software

libapache2-mod-uwsgi provides /etc/apache2/mods-available/proxy_uwsgi.load
and /usr/lib/apache2/modules/mod_proxy_uwsgi.so and enables the module in
the postinst:
apache2_invoke enmod @@module_name@@  || exit 1
https://sources.debian.net/src/uwsgi/2.0.12-7/debian/libapache2-mod-__MODULE__.postinst.in/

However, https://sources.debian.net/src/uwsgi/2.0.12-7/debian/libapache2-mod-__MODULE__.prerm.in/ seems to fail to dismod on purge:

Original log is from jessie:

$ sudo apt --purge remove  libapache2-mod-uwsgi libapache2-mod-wsgi
Removing libapache2-mod-uwsgi (2.0.7-1) ...
Purging configuration files for libapache2-mod-uwsgi (2.0.7-1) ...
Removing libapache2-mod-wsgi (4.3.0-1) ...
ERROR: Can't open /etc/apache2/mods-enabled/uwsgi.load: No such file or directoryModule wsgi disabled.
apache2_invoke prerm: Disable module wsgi
apache2_reload: Your configuration is broken. Not restarting Apache 2
apache2_reload: apache2: Syntax error on line 140 of /etc/apache2/apache2.conf: Could not open configuration file /etc/apache2/mods-enabled/uwsgi.load: No such file or directory
Purging configuration files for libapache2-mod-wsgi (4.3.0-1) ...
apache2_invoke postrm: Purging state for wsgi

Not restarting Apache on a server which is providing multiple hosts is
very bad, especially as apt|dpkg exits cleanly. Unless the admin is
watching the purge output directly, the reason for the server going
offline would not be obvious.

Once the problem is spotted:
$ sudo a2dismod uwsgi
$ sudo apache2ctl restart

... does allow apache to restart successfully.

Reproduced in a sid VM:
$ sudo apt install libapache2-mod-uwsgi libapache2-mod-wsgi
....
$ sudo apache2ctl -M|grep wsgi
AH00558: apache2: Could not reliably determine the server's fully qualified domain name, using 127.0.1.1. Set the 'ServerName' directive globally to suppress this message
 uwsgi_module (shared)
 wsgi_module (shared)
neil at debian-sid:~$ sudo apt --purge remove libapache2-mod-uwsgi libapache2-mod-wsgi
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages were automatically installed and are no longer required:
  libjansson4 libmatheval1 libpython2.7 libsodium18 libyaml-0-2 libzmq5
  uwsgi-core
Use 'sudo apt autoremove' to remove them.
The following packages will be REMOVED:
  libapache2-mod-uwsgi* libapache2-mod-wsgi*
0 upgraded, 0 newly installed, 2 to remove and 0 not upgraded.
After this operation, 342 kB disk space will be freed.
Do you want to continue? [Y/n]
(Reading database ... 46879 files and directories currently installed.)
Removing libapache2-mod-uwsgi (2.0.12-7) ...
Removing libapache2-mod-wsgi (4.5.7-1) ...
Module wsgi disabled.
apache2_invoke prerm: Disable module wsgi
apache2_reload: Your configuration is broken. Not restarting Apache 2
apache2_reload: apache2: Syntax error on line 140 of /etc/apache2/apache2.conf: Syntax error on line 1 of /etc/apache2/mods-enabled/uwsgi.load: Cannot load /usr/lib/apache2/modules/mod_uwsgi.so into server: /usr/lib/apache2/modules/mod_uwsgi.so: cannot open shared object file: No such file or directory
(Reading database ... 46865 files and directories currently installed.)
Removing libapache2-mod-wsgi (4.5.7-1) ...
Purging configuration files for libapache2-mod-wsgi (4.5.7-1) ...
apache2_invoke postrm: Purging state for wsgi
Removing libapache2-mod-uwsgi (2.0.12-7) ...
Purging configuration files for libapache2-mod-uwsgi (2.0.12-7) ...

$ sudo service apache2 restart
Job for apache2.service failed because the control process exited with error code.
See "systemctl status apache2.service" and "journalctl -xe" for details.
$ sudo service apache2 status
● apache2.service - The Apache HTTP Server
   Loaded: loaded (/lib/systemd/system/apache2.service; enabled; vendor preset: enabled)
   Active: failed (Result: exit-code) since Mon 2016-10-03 17:22:08 BST; 3s ago
  Process: 27997 ExecStop=/usr/sbin/apachectl stop (code=exited, status=1/FAILURE)
  Process: 28004 ExecStart=/usr/sbin/apachectl start (code=exited, status=1/FAILURE)
 Main PID: 27843 (code=exited, status=0/SUCCESS)

Oct 03 17:22:08 debian-sid systemd[1]: apache2.service: Failed with result 'exit-code'.
Oct 03 17:22:08 debian-sid systemd[1]: Starting The Apache HTTP Server...
Oct 03 17:22:08 debian-sid apachectl[28004]: apache2: Syntax error on line 140 of /etc/apache2/apache2.conf: Could not open configuration file
Oct 03 17:22:08 debian-sid apachectl[28004]: Action 'start' failed.
Oct 03 17:22:08 debian-sid apachectl[28004]: The Apache error log may have more information.
Oct 03 17:22:08 debian-sid systemd[1]: apache2.service: Control process exited, code=exited status=1
Oct 03 17:22:08 debian-sid systemd[1]: Failed to start The Apache HTTP Server.
Oct 03 17:22:08 debian-sid systemd[1]: apache2.service: Unit entered failed state.
Oct 03 17:22:08 debian-sid systemd[1]: apache2.service: Failed with result 'exit-code'.

Again, sudo a2dismod uwsgi fixes the problem.

- System Information:
Debian Release: stretch/sid
  APT prefers unstable
  APT policy: (500, 'unstable'), (500, 'testing'), (500, 'stable'), (1, 'experimental')
Architecture: amd64 (x86_64)
Foreign Architectures: i386, armhf, arm64

Kernel: Linux 4.7.0-1-amd64 (SMP w/4 CPU cores)
Locale: LANG=en_GB.utf8, LC_CTYPE=en_GB.utf8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages libapache2-mod-uwsgi depends on:
ii  apache2-bin [apache2-api-20120211]  2.4.23-5
ii  libapr1                             1.5.2-4
ii  libaprutil1                         1.5.4-2
ii  libc6                               2.24-3

Versions of packages libapache2-mod-uwsgi recommends:
pn  uwsgi-core  <none>

Versions of packages libapache2-mod-uwsgi suggests:
pn  uwsgi  <none>

-- no debconf information