service-config-manager performance issue

[Jiaqing Zhao]

Just had a discussion with the original author of that function, the 15s wait here is used to accommodate multiple config changes in single restart. If remove this wait, each service change will trigger systemd reload, which causes race condition and loss of data.

So for services controlled by service-config-manager, both get and set operations should call the manager's DBus. An example is intel-ipmi-oem (https://github.com/openbmc/intel-ipmi-oem/blob/master/src/bmccontrolservices.cpp). But in bmcweb, the get is implemented by calling systemd DBus directly,
so the properies in Redfish will not reflect the changes immediately. I will submit a patch to fix it. 

On 2022-02-22 04:00, Joseph Reynolds wrote:
> On 2/21/22 6:41 AM, Jiaqing Zhao wrote:
>> Hi, all
>>
>> When updating service status with service-config-manager, it always takes ~15s for the new status to be applied, which is much longer than it should be.
>>
>> By inspecting the code, I found there is a 15s wait before updating service status in ServiceConfig::startServiceRestartTimer(). (https://github.com/openbmc/service-config-manager/blob/f2744893b77b9dd8903bb13113f4c3ef62c18f04/src/srvcfg_manager.cpp#L382)
>>
>> The 15s-wait is added at first in commit 0084047 (https://github.com/openbmc/service-config-manager/commit/0084047d008fd0ac36f09a232f67ff2fc5314b53).
> 
> Here at IBM we are seeing the same thing.  It looks like that code (https://github.com/openbmc/service-config-manager/blob/master/src/srvcfg_manager.cpp - ServiceConfig::startServiceRestartTimer) was part of the initial commit.  I wonder if the problem is caused by a bug in that code.  (But I am not familiar with the code, and I don't have time to look at it now.)  Is the intention to reload the systemd units but give up after 15 seconds?
> 
> Joseph
> 
>> I've tested service-config-manager works as expected with the wait removed, and it only takes ~1s for the settings being applied, shall we remove it? And I'd like to ask what is the purpose of this wait to double confirm if removing it will bring any side effect.
>>
>> Thanks,
>> Jiaqing
>