DomInfoUpdateTask polling period DOM_INFO_UPDATE_PERIOD_SECS improperly delays polling

[aditya-nexthop]

DOM_INFO_UPDATE_PERIOD_SECS should be the time delay between polling information from a specified interface, say Ethernet0

So the expectation is:

Polled Ethernet0 @ t=0
Polled Ethernet4 @ t = ...
...
Polled Ethernet200 @ t = X

Polled Ethernet0 @ t=DOM_INFO_UPDATE_PERIOD_SECS

Instead what we see is:

Polled Ethernet0 @ t=0
Polled Ethernet4 @ t = ...
...
Polled Ethernet200 @ t = X

Polled Ethernet0 @ t=X+DOM_INFO_UPDATE_PERIOD_SECS

This means no information is polled from any transceiver for DOM_INFO_UPDATE_PERIOD_SECS after the polling loop completes, even though more time than DOM_INFO_UPDATE_PERIOD_SECS may have elapsed since Ethernet0 was polled.

This is due to the following code:

class DomInfoUpdateBase(threading.Thread):
...
    def task_worker(self):
...
        # Start loop to update dom info in DB periodically and handle port change events
        while not self.task_stopping_event.is_set():
            # Check if periodic db update is needed
            if next_periodic_db_update_time <= datetime.datetime.now():
                is_periodic_db_update_needed = True
...
            for physical_port, logical_ports in self.port_mapping.physical_to_logical.items():
...
            if is_periodic_db_update_needed:
                next_periodic_db_update_time = datetime.datetime.now() + \          <<===============
                                               datetime.timedelta(seconds=dom_info_update_periodic_secs)
                is_periodic_db_update_needed = False

In order to enforce proper timing delay, now should be set at the start of the loop and used at the highlighted place to set next_periodic_db_update_time