test_reload_config.py test failure due to interface-config.service dependency

[anamehra]

Description
test_reload_config test case has a dependency on interfaces-config.service. In a test to validate config reload failure when swss is not up, the test checks for interfaces-config.service state (https://github.com/sonic-net/sonic-mgmt/blob/master/tests/platform_tests/test_reload_config.py#L129) to be up to test config reload, expecting swss is not up at that time. This change was introduced by #7289
This code assumes that the swss service has a dependency on interface-config.service and starts after the interface-config, which was the case earlier. This dependency was removed a year ago via sonic-net/sonic-buildimage#13084

There is no direct dependency between interfaces-config and swss, so systemd won't guarantee swss service starts only after interfaces-config.

Steps to reproduce the issue:
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Describe the results you received:

Describe the results you expected:

Additional information you deem important:

**Output of `show version`:**

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**Attach debug file `sudo generate_dump`:**

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[anamehra]

Hi @abdosi , @JibinBao , @stepanblyschak , for your viz. Thanks

[stepanblyschak]

Hi @anamehra, I am looking at the test code, not sure I understand why test expects swss.service to depend on interfaces-config.service, also, why "config reload" should throw an error?

[anamehra]

Hi @stepanblyschak , the test code validates a negative scenario where config reload should fail when swss is not up yet. It relies on the timing to run the command right at the moment when redis is accessible but swss has not started yet and I think interfaces-config check was introduced just to achieve ive that. Given that swss has no dependency on interfaces-config now, the test case needs to change. I think instead of validating this negative scenario during boot, it should just explicitly stop swss and validate that config reload fails.

[stepanblyschak]

@anamehra Thanks, so as I understand "config reload" should fail when swss is down, any reason why? "config reload" cold restarts all services, so not sure such check in "config reload" is needed or are there any issues restarting services when swss is down?

[JibinBao]

@dgsudharsan, Can you help check the above issue? If there is no direct dependency between interfaces-config and swss, shoud we revert the fix #7289? And then how to stabilize the test_reload_configuration_checks?

[dgsudharsan]

@anamehra This check was introduced to overcome a race condition where config reload gets executed while interface-services.config is running and the loopback ip is not accessible giving traceback for the command the resulting in the test failure. Below is example

Jan  4 06:29:19.434440 r-bulldog-02 INFO systemd[1]: Starting Update interfaces configuration...
Jan  4 06:29:21.659292 r-bulldog-02 INFO python[11575]: ansible-command Invoked with executable=/bin/bash _uses_shell=True _raw_params=sudo config reload -y warn=True stdin_add_newline=True strip_empty_ends=True argv=None chdir=None creates=None removes=None stdin=None
Jan  4 06:29:25.786037 r-bulldog-02 INFO systemd[1]: Finished Update interfaces configuration.

You will get

File "/usr/local/...: Unable to connect to redis: Cannot assign requested address

However this issue was fixed by @saiarcot895 sonic-net/sonic-buildimage#15080. Given we have this fix the change in sonic-mgmt can be reverted.

@JibinBao please revert the change to check interface-services.config.

[JibinBao]

Fixed:
#11674
#11675