Creating Label with filename value out of filename (Path)

Grafana Alloy
1

Hey everyone,

my Problem this time is that i want to have a repeating variable in Grafana that repeats for every different Log name. So Label Log and value server.log, app.log, error.log. I do not want to aggregate them. I want this per app and there can be multiple on one machine.

Server1

Prod
C:\Program\app\logs*.log
C:\Program\app\webserver\logs*.log

Test
C:\Program\apptest\logs*.log
C:\Program\apptest\webserver\logs*.log

Server 2
…

“filename” Label that is created automatically looks like this then

C:\Program\app\webserver\logs\server.log

This gives me an error if i want to repeat over filename cause of escaping as the \ is not doubled in that path.

My idea to solve this was to use just the filename so “log” = “server.log”,“app.log” etc. to then search this as filename =~ “.*$log” in Grafana.

I tried filtering the filename like this:

stage.regex {
source = “filename”
expression = “(?[^\\]+)$”
}

stage.static_labels {
values = {
Log = “log”,
}
}
And i guess this should work but i couldn’t confirm because i only get log like this.

So my question is how do i get this label “Log” to have the different values of filenames?
Or does anyone have another simpler solution for the problem that can be done without matching everything individually?

2

Couple of issues:

  1. Your regex group capture is incomplete (no group name).
  2. If you use double quote in stage.regex you need to double escape special character. I recommend using ` character instead.
  3. static_labels is for setting hard coded labels. You want stage.labels instead.

I would also recommend using a label name that makes more sense, perhaps filename_basename? But this is up to you.

Something like this (not tested):

  stage.regex {
    expression = `(?<basename_parsed>[^\\]+)$`
    source = "filename"
  }

  stage.labels {
    values = { filename_basename = "basename_parsed" }
  }
3

Thanks @tonyswumac ,

This works like a charm. I had the capture group in before but tried some stuff out. Also thanks for the tipps.

Also do you happen to Know where you can read up on this?

stage.labels {
values = { filename_basename = “basename_parsed” }
}

I didn’t find anything that really explains ho to do this in the Documentation.

4

If you are referring to the stage.labels block, you can find it here loki.process | Grafana Alloy documentation

If you are referring to the filename label being provided by the source.file block, it’s here: loki.source.file | Grafana Alloy documentation

5

those i found it was more about the creating a Label our of a Capture group. Now that i did it i rembember seeing it once in an example somewhere but i didn’t connect it to my problem.