Support data path in Global Variable query

[ggranberry]

Currently when trying to assign a result from a Graphql Datasource into a Global Variable, there is no option to specify a data path leading to an inability to assign any values

[ggranberry]

I can tackle this PR if you want to assign it to me.

[retzkek]

Thanks for opening this issue, to be honest I haven't looked into what it would take to support using the datasource for query variables. Historically this has been rather disconnected from the datasource, with a unique editor, query language, etc. I see there's now some documentation on supporting query variables, looks pretty straightforward.

[retzkek]

@ggranberry absolutely, let me know if you run into any issues. The main challenge I see is that we need to ensure that we get an array of simple values out, rather than objects.

[ggranberry]

@retzkek How would you recommend implementing metricFindQuery? I was thinking of just calling query and then parsing the output

[retzkek]

@ggranberry Good question... my first instinct is to use createQuery() and getDocs() directly, since there's a lot of extra stuff that query() handles (multiple targets, time fields, grouping, aliases) that shouldn't apply in this context.

[ggranberry]

Hey just getting back to this and I was wondering if you had any documentation on how to build/test this? I was just going to try to install it into a local grafana docker image to test it out. Do I need to do anything besides copy this dir to the plugins folder?

[retzkek]

Yep that's all there is to it, or you can set the Grafana plugins directory, e.g. if I have the repo at /Users/kretzke/fifemon/graphql-datasource:

/usr/local/bin/grafana-server --homepath /usr/local/share/grafana cfg:default.paths.plugins=/Users/kretzke/fifemon

Or with Docker:

docker run -it --rm -v /Users/kretzke/fifemon:/var/lib/grafana/plugins -p 3000:3000 grafana/grafana

Note that you need to restart Grafana anytime you've changed the plugin (after running yarn dev).

[ggranberry]

PR is up whenever you have time to review 👍