Add support for a dashboard-level datasource setting

[tpoon]

This adds an optional "Datasource" setting at the Dashboard level that overrides the individual graph-level settings. We have found this to be very helpful for re-using the same dashboard across multiple data sources.

Usage

1. Enable in dashboard settings.

2. Select the Datasource at the top of the page. This updates the datasource settings on all the graphs in the dashboard.

3. This works together with the filters. For example, the possible values for a filter are updated whenever you switch the data source.

[torkelo]

Nice, this looks really useful. Will try to merge with the next couple of days.

[torkelo]

Please sign the contributor license agreement http://grafana.org/docs/contributing/cla.html

[tpoon]

Sure, I just submitted it.

[edasque]

I'd love for this to be merged since Filters only work on the default datasource. As a result, we can't use it on any dashboard that isn't based on the default DS.

[torkelo]

@edasque it is waiting for an overhaul of the filter system planed for v1.8.

[ruiqiding]

Can we specify row level or dashboard level data source from scripted dashboard please?

e.g.

return {
title: title,
height: height,
panels: panels,
datasource: 'DC_EU' //For example
};

[edasque]

👍 especially if it includes support for templating at the dashboard level (you could also make it at the row or even graph level I guess by adding datasource variable to the datasource graph dropdown).

[torkelo]

would like to have something like this, maybe via #1055