Google Cloud App Engine（python）：从device1接收帖子并将帖子发送到设备2

Question

I have a Google Cloud project with consists in a SQL database and App Engine in python 2.7.

Up to know what I have done is from a RaspberryPi send a post to App Engine and save data in the Cloud. At the same time this RasPi was able to receive data from the Cloud or App Engine thanks to the code: self.response.write(jsondata). This works fine.

Now I introduced a new device in the system, which I will call Raspi2. Raspi 1, sends a command to App Engine, and I want App Egine to send this command to Raspi2, without Raspi2 needs to ask peridically the cloud, to avoid delay. Is there a way of telling AppEngine to send a message to another device, how? Or if not App Engine, that when an specific field in the SQL table has changed, triggers a message to be sent to Raspi3, without Polling. I don't know if it possible to do it, I have read about Google cloud Messaging, but I don't know if it applies to this case.

Thanks

Answer 1

This is called a server push to a client. App engine used to have a channel api that allowed you to do this but it has now been deprecated and might not be available at all.

Firebase realtime database is the recommended replacement.