[ClusterLabs] Failed 'virsh' call when test RA run by crm_resource (con't)

[Madison Kelly]

On 2023-01-12 01:26, Reid Wahl wrote:
> On Wed, Jan 11, 2023 at 10:21 PM Madison Kelly <mkelly at alteeve.com> wrote:
>>
>> On 2023-01-12 01:12, Reid Wahl wrote:
>>> On Wed, Jan 11, 2023 at 8:11 PM Madison Kelly <mkelly at alteeve.com> wrote:
>>>>
>>>> Hi all,
>>>>
>>>>      There was a lot of sub-threads, so I figured it's helpful to start a
>>>> new thread with a summary so far. For context; I have a super simple
>>>> perl script that pretends to be an RA for the sake of debugging.
>>>>
>>>> https://pastebin.com/9z314TaB
>>>>
>>>>      I've had variations log environment variables and confirmed that all
>>>> the variables in the direct call that work are in the crm_resource
>>>> triggered call. There are no selinux issues logged in audit.log and
>>>> selinux is permissive. The script logs the real and effective UID and
>>>> GID and it's the same in both instances. Calling other shell programs
>>>> (tested with 'hostname') run fine, this is specifically crm_resource ->
>>>> test RA -> virsh call.
>>>>
>>>>      I ran strace on the virsh call from inside my test script (changing
>>>> 'virsh.good' to 'virsh.bad' between running directly and via
>>>> crm_resource. The strace runs made six files each time. Below are
>>>> pastebin links with the outputs of the six runs in one paste, but each
>>>> file's output is in it's own block (search for file: to see the
>>>> different file outputs)
>>>>
>>>> Good/direct run of the test RA:
>>>> - https://pastebin.com/xtqe9NSG
>>>>
>>>> Bad/crm_resource triggered run of the test RA:
>>>> - https://pastebin.com/vBiLVejW
>>>>
>>>> Still absolutely stumped.
>>>
>>> The strace outputs show that your bad runs are all getting stopped
>>> with SIGTTOU. If you've never heard of that, me either.
>>
>> The hell?! This is new to me also.
>>
>>> https://www.gnu.org/software/libc/manual/html_node/Job-Control-Signals.html
>>>
>>> Macro: int SIGTTOU
>>>
>>>       This is similar to SIGTTIN, but is generated when a process in a
>>> background job attempts to write to the terminal or set its modes.
>>> Again, the default action is to stop the process. SIGTTOU is only
>>> generated for an attempt to write to the terminal if the TOSTOP output
>>> mode is set; see Output Modes.
>>>
>>>
>>> Maybe this has something to do with the buffer settings in the perl
>>> script(?). It might be worth trying a version that doesn't fiddle with
>>> the outputs and buffer settings.
>>
>> I tried removing the $|, and then I changed the script to be entirely a
>> bash script, still hanging. I tried 'virsh --connect <method> list
>> --all' where method was qemu:///system, qemu:///session, and
>> ssh+qemu:///root@localhost/system, all hang. In bash or perl.
>>
>>> I don't know which difference between your environment and mine is
>>> relevant here, such that I can't reproduce the issue using your test
>>> script. It works perfectly fine for me.
>>>
>>> Can you run `stty -a | grep tostop`? If there's a minus sign
>>> ("-tostop"), it's disabled; if it's present without a minus sign
>>> ("tostop"), it's enabled, as best I can tell.
>>
>> -tostop is there
>>
>> ====
>> [root at mk-a07n02 ~]# stty -a | grep tostop
>> isig icanon iexten echo echoe echok -echonl -noflsh -xcase -tostop -echoprt
>> [root at mk-a07n02 ~]#
>> ====
>>
>>> I'm just spitballing here. It's disabled by default on my machine...
>>> but even when I enable it, crm_resource --validate works fine. It may
>>> be set differently when running under crm_resource.
>>
>> How do you enable it?
> 
> With `stty tostop`
> 
> It's 100% possible that this whole thing is a red herring by the way.
> I'm looking for anything that might explain the discrepancy. SIGTTOU
> may not be directly tied to the root cause.

Appreciate the stab, didn't stop the hang though :(

-- 
Madison Kelly
Alteeve's Niche!
Chief Technical Officer
c: +1-647-471-0951
https://alteeve.com/