|Summary:||`ExtendedStatus Off` directive when using mod_systemd causes systemctl to hang|
|Product:||Apache httpd-2||Reporter:||Doug Knight <doug.knight>|
|Component:||Other Modules||Assignee:||Apache HTTPD Bugs Mailing List <bugs>|
|Attachments:||(UNTESTED) Proposed Resolution|
Description Doug Knight 2018-09-07 20:20:17 UTC
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.
Comment 1 Doug Knight 2018-09-07 20:41:03 UTC
Created attachment 36140 [details] (UNTESTED) Proposed Resolution I am attaching a patch illustrating what I believe would address this issue.
Comment 2 Doug Knight 2018-09-07 22:11:40 UTC
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.
Comment 3 Joe Orton 2018-09-11 12:45:33 UTC
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.)