Best data structure for IOT application -> dynamic collections

help
1

Hello,

I am writing a simple HomeIOT application that my local ESP8266 devices with DHT22 sensors will send their data to every few minutes. It will have a dashboard (currently in materializecss) that allows uses to add devices with a name, passcode and the fields for the data being sent. I have easily made the devices and dashboard however I’m currently a little stuck and needing assistance for the layout.

I was planning on utilising mongodb to store the data using a simple rest API. This would allow each device to post to a url which would then verify the name, the code and then push the fields into a new document that would be rendered in the charts.

However, I am unsure how to dynamically add a collection when a device is made, such that each device has its own collection for the data being sent.

Should i dynamically make a collection that can have data added to it… i.e.:

Device name: ‘Inside_DHT22’ … then i was considering making a collection something similar to: ‘data_Inside_DHT22’ which i would then call in the rest API.

I was hoping to make similar collections for every device made, as to avoid mixing data for multiple devices in a single collection.

Is there any advice you can give me on the best way to structure this? or would one collection suffice with each document containing a name field to identify the device it is from?

If you were to suggest making a collection for each device ( assuming they push new data every 5 minutes, and runs 24/7), and if so, how would is the best way to do that when the number of devices being added is unknown?

Regards,
Jeremy

2

I’m curious as to why you think data should not be mixed, given that it can be reliably identified?

It’s generally good practise to keep like data together - and it (hugely) simplifies the design and workflow.

The most important thing (however you do it) is to ensure you set up indexes appropriately.

3

Im unsure to be honest, I’m new to Meteor and mongo and just preferred having it separated, but having posted this i have combined the data :slight_smile: How would you set up the indexes? any particular advice for a new person to Meteor?

4

You should determine the indexes from your query requirements (MongoDB is not really any different from SQL in this regard). So, MongoDB gives you an index “for free” on _id, but it sounds like you will at least need an index on device as well - but you will likely have more. For example, if you want to return documents in the order they were written, you may need to add a createdAt field (you could look at aldeed:simple-schema with aldeed:collection2 or matb33:collection-hooks for this). It may then make sense to use a composite index ({device:1, createdAt:1}) rather than multiple, separate indexes. Again, only you understand your requirements, so you will need to do this analysis yourself.

To add indexes to a collection in Meteor, the normal practise is to put the code in the server’s Meteor.startup(), for example:

Meteor.startup(function() {
  MyCollection._ensureIndex({device:1, createdAt:1});
});
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