Warning when creating an Alert: "Expression warning - 1 items dropped from union(s): ["${B} > 1.000000": (1.000000: {})]"

I’m getting this warning when I try to add an alert. I simply want to create an alert when there’s a new log that contains the word “login.” Quite simple but it doesn’t work, even if there are “login” word inside the logs in the last few minutes, Loki finds “No data” and the warning:

What I’m doing wrong?


A query doesn’t return any data:

so then B has no data and then C has no data.

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Okay thank you, now I got this. I tried with a word already in the logs and it works.

But if I want to get an alert when there’s a new word/phrase (e.g. “This plugin slows down Homebridge”), it’s normal that this phrase usually isn’t in the log, so I get a “no data” message. I want an alert right when that word appears :blush:
So the only way to configure the alert is to set it up as I have done, even if Grafana reports “no data” and then configure the “No data and error handling” option like this:

Now, I should get this notification when Loki/Grafana finds the word. But is this the correct way?


It looks good to me. Set Pending period: 0 and test it = generate that log line and observe if it works as expected.
IMHO you can use also previous alert setup - it was only a warning, not real error.


Yes it’s working thanks!