Modifying subscription problem

[Dawik98]

I have been testing Opc Data Logger from softwaretoolbox and had a problem where I could log variables at most once a second. After closer inspection with Wireshark, I found out that when the client tried to change sampling interval of the subscription with ModifySubscriptionRequest, the server ignored it and kept using initialized SamplingInterval. It happend to be 1 second, which explains the clients behavior.

I found function that is responsible for handling ModifySubscriptionRequest inside subscription_service.py I modified the function as shown below which fixed the issue. The function has however a comment: Requested params are ignored, result = params set during create_subscription. Is it any reason for why modifying a subscription has been ignored?

    def modify_subscription(self, params, callback):
        self.logger.info("modify subscription with callback: %s", callback)

        result = ua.ModifySubscriptionResult()
        try:
            sub = self.subscriptions[params.SubscriptionId]

            sub.data.RevisedPublishingInterval = params.RequestedPublishingInterval
            sub.data.RevisedLifetimeCount = params.RequestedLifetimeCount
            sub.data.RevisedMaxKeepAliveCount = params.RequestedMaxKeepAliveCount

            result.RevisedPublishingInterval = sub.data.RevisedPublishingInterval
            result.RevisedLifetimeCount = sub.data.RevisedLifetimeCount
            result.RevisedMaxKeepAliveCount = sub.data.RevisedMaxKeepAliveCount

            return result
        except KeyError:
            raise utils.ServiceError(ua.StatusCodes.BadSubscriptionIdInvalid)