Re: [mosquitto-dev] Can you use mosquitto /mqtt to track changes in data

[Marl Li <happydevdays@xxxxxxxxx>]

Thanks for the response.  I've read other articles where people have tried similar things using triggers.  But once the database triggers a message to the mqtt topic saying "hey everyone, there's a change", we still need a way to get the data out.  

So, the next question I have is how big can the mqtt message be? 

and are there limitations on what the message can contain? 

I don't plan on putting the actual changed data in the message... but nonetheless, I need to know how big the message can be to design the rest of the solution.

In my case, I'm hoping the end point will be an HTTP application on a server... so it will subscribe the mqtt topic and listen for changes.

Is that possible? 

Hi Marl

I've never tried this using MQTT, <but>, it should be possible to use MQTT paho lib as the communication medium between your mobile device(s) and the trigger-event system. One part will be to setup (pending on the database) triggers that "watch" for change(s) and inside the trigger you need to hook in your notification system sending a MQTT message....basic idea is - the database trigger and pub a message to say mosquitto - you have to thing carefully on how you going to use our topic's for this sort of "notifications" ....

I when work with topics I normally look at the end-point,...the system subscribing to topics...what will the application LISTEN for and what will it do with the payload...so in this instance, the mobile phone or desktop is the end point....

But I think it should be possible - you can even use the trigger on database side to drop the info in a Queue and get workers to pub MQTT message for people to get....it all depends on what is possible on the database trigger side ;)

My 2 sent worth of option/input

Hope it helps a bit....

On Tue, Jan 13, 2015 at 10:29 PM, Marl Li <happydevdays@xxxxxxxxx> wrote:

Hi. Has anyone tried using mqtt to track and share changes in a database? 

specifically, when data in a database changes i would like to notify some interested parties, and provide a way for them to get at the data. 

Is this possible using mqtt? 

Thanks.