[snmp.service] Make swss.service a requisite for snmp.service

[stepanblyschak]

Trying to address #2750 by removing snmp.service required dependency on swss.service and adding it as requisite

Signed-off-by: Stepan Blyschak stepanb@mellanox.com

- What I did

- How I did it

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- Description for the changelog

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[stepanblyschak]

When swss.service failed, snmp.service fails and restart of swss.service does not start snmp.service when using Requisite.
However Requires has the same behaviour if swss and snmp failed to start.

[jleveque]

@stepanblyschak: Can you clarify your last comment? Are you stating a problem here? A restart of swss.service should also restart snmp.service. This is the behavior we want, and it I believe this should happen with both Requires and Requisite. The behavior we don't want is for a call to start snmp.service to also attempt restarting swss.service if it is stopped -- Requires causes this to happen, whereas Requisite should not.

[stepanblyschak]

@jleveque
"A restart of swss.service should also restart snmp.service" - this works as expected
"don't want is for a call to start snmp.service to also attempt restarting swss.service if it is stopped" - this works as expected

If swss.service is stopped/inactive and snmp.service is stopped/inactive restart of swss.service does not start snmp.service. Is this desired?

[stepanblyschak]

@jleveque Similar behaviour as described for dhcp_relay here: #2752

[jleveque]

I see. OK. Then this behavior should be fine. Once I add in the changes I describe in the issue you linked, the latter behavior should also work.