How can i turn no data to zero in Loki

Grafana Loki
1

Hi all , Im looking for a way to turn the null/no data return to zero in logql. Im trying to get the percent of the request just like

sum(count_over_time({app="xxx"}|="{"|json|route="POST /api/a" , status=~`200|400|401|403|429|404` [1m])) / sum(count_over_time({app="xxx"}|="{"|json|route="POST /api/a" [1m]))

But when there is no 200|400|401|403|429|404 of /api/a the return of sum(count_over_time({app="xxx"}|="{"|json|route="POST /api/a" , status=~200|400|401|403|429|404 [1m])) is no data ,and i wanna turn it to zero. So the total result can be 0%

7 Likes
2

This is a good question, I’m not sure if this is currently possible but will ask the team for options here!

2 Likes
3

I am also interested in this. Any way to make a logql query return zero when theres no data ?

4

It’d be really helpful to get an answer on this. Now that we can alert based on Loki LogQL metric queries, sending alerts based on error logs seems like a common use case. But if your query returns no data when there are no error logs, it’s impossible to get your alert to work properly.

2 Likes
5

this is a useful feature, like the or on() vector(0) in prometheus query, which will help on alerting and also some calculation.

Any progress on it?

2 Likes
6

Came up with kinda ugly solution. Basic idea is that you should negate your regexp first, and than subtract this value from sum without conditions. Something like this:
sum(x) - sum ( x | code !~"^5…")

7

I agree that this is a useful feature.
For example if I display graph line of number of errors in logs - if there are none I want it to be displayed as 0 and that it won’t disappear from the graph.

8

I used a Grafana transformation which seems to work

Add field from calculation → Binary operation
Select the query and do + 0
I then hide the original query

It would be easier if we could do this in the original query though

9

Agreed! I opened a discussion on Github as well to follow this: How can i turn no data to zero in Loki · Discussion #39742 · grafana/grafana · GitHub

10

If we have an option to join with a vector of 0 and do a sum, would be good.

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I would like this too!

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[doc] logql: logql engine support exec vector(0) grama #7044