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Posted to bugs@httpd.apache.org by bu...@apache.org on 2018/09/07 20:20:17 UTC

[Bug 62697] New: `ExtendedStatus Off` directive when using mod_systemd causes systemctl to hang

https://bz.apache.org/bugzilla/show_bug.cgi?id=62697

            Bug ID: 62697
           Summary: `ExtendedStatus Off` directive when using mod_systemd
                    causes systemctl to hang
           Product: Apache httpd-2
           Version: 2.5-HEAD
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: Other Modules
          Assignee: bugs@httpd.apache.org
          Reporter: doug.knight@karmix.org
  Target Milestone: ---

When using mod_systemd on a system with a systemd httpd service of type notify,
we have encountered a scenario where the command `systemctl reload httpd` never
returns.  In this case, systemd continues to report the service as reloading,
even though httpd respawned all of its server processes.

I have tracked the problem down to the way in which an `ExtendedStatus Off`
directive in the local configuration is interacting with the code introduced
here: http://svn.apache.org/viewvc?view=revision&revision=1802251 .  The
general sequence of events is:

1. User runs `systemctl reload httpd`.
2. systemd forks off an `httpd -k graceful` process, which exits successfully.
3. mod_systemd's systemd_pre_config hook sends a notification to systemd that
httpd is reloading, then sets ap_extended_status.
4. While reloading its configuration, httpd responds to an `ExtendedStatus Off`
directive by clearing ap_extended_status.
5. Subsequent calls to mod_systemd's systemd_monitor hook short-circuit when
they see that ap_extended_status is cleared so httpd stops sending status
updates to systemd.
6. systemd indefinitely reports httpd's state as reloading because it never
receives a READY=1 notification from mod_systemd's systemd_monitor hook.
7. The `systemctl reload httpd` command never exits.

I would expect httpd tell systemd when it finished reloading its configuration
regardless of the state of ap_extended_status.  I believe sending a
notification such as "READY=1\nSTATUS=ExtendedStatus is disabled." before
short-circuiting when ap_extended_status is cleared should resolve the issue,
but I haven't had an opportunity to setup a build environment to confirm.

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[Bug 62697] `ExtendedStatus Off` directive when using mod_systemd causes systemctl to hang

Posted by bu...@apache.org.
https://bz.apache.org/bugzilla/show_bug.cgi?id=62697

--- Comment #2 from Doug Knight <do...@karmix.org> ---
I have tested the previously attached patch by rebuilding the httpd package in
Amazon Linux 2 (httpd-2.4.34-1.amzn2.1.0 including vendor patches), and
confirmed that `systemctl reload httpd` returns properly after the patch is
applied in that environment.  I still do not have a pristine build environment.

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[Bug 62697] `ExtendedStatus Off` directive when using mod_systemd causes systemctl to hang

Posted by bu...@apache.org.
https://bz.apache.org/bugzilla/show_bug.cgi?id=62697

--- Comment #3 from Joe Orton <jo...@redhat.com> ---
Good catch, thanks for the report and patch.  I think it would be slightly
better to do the READY=1 in a post_config hook actually outside of the monitor
hook.  At this point the serer is listening TCP ports so should be acceptable
to say the service is "started".  (There is a slight trade-off here since we
can't guarantee some failure after saying READY=1 before entering the MPM, but
that could happen anyway.)

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[Bug 62697] `ExtendedStatus Off` directive when using mod_systemd causes systemctl to hang

Posted by bu...@apache.org.
https://bz.apache.org/bugzilla/show_bug.cgi?id=62697

Joe Orton <jo...@redhat.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED

--- Comment #4 from Joe Orton <jo...@redhat.com> ---
Committed in r1840554, please test it if you can!

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[Bug 62697] `ExtendedStatus Off` directive when using mod_systemd causes systemctl to hang

Posted by bu...@apache.org.
https://bz.apache.org/bugzilla/show_bug.cgi?id=62697

--- Comment #1 from Doug Knight <do...@karmix.org> ---
Created attachment 36140
  --> https://bz.apache.org/bugzilla/attachment.cgi?id=36140&action=edit
(UNTESTED) Proposed Resolution

I am attaching a patch illustrating what I believe would address this issue.

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