Grafana: select host for a dashboard

InfluxDB is running on a Raspberry Pi in my home network (with separate attached disk), and I installed a Grafana on top of it, to visualize crucial data.

In Grafana it is possible to define a variable for a dashboard and this variable can query the data source and use the returned list of values. Let’s say the variable is $host, then the data query can use:

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WHERE host =~ /^$host$/

and limit the current dashboard to the selected host. Also the variable will provide a select field at the top of the dashboard, which allows selecting the system one wants to see:

Now usually - according to the documentation - a SHOW TAG VALUES in the data source should be sufficient However as it is, this did not work for me, and the query came back empty:

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> show tag values from system with key = host

Looks like I’m not the only one with this problem.

Luckily there is a way around with another query:

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select distinct("host") from (select "host","load1" from system)

The result:

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> select distinct("host") from (select "host","load1" from system)
name: system
time distinct
---- --------
0    host1
0    host2
0    host3
0    host4
0    host5
0    host6

Grafana ignores the time column and uses the second column for the host list. Voila.