In my FluentBit config I have the following output:

 [Output]
    name loki
    match *
    host loki
    port 3100
    labels container_name=$container_name $log_type
    line_format json

And it works fine, I can see in Loki corresponding labels existing, but they have white space between container name and log type. I’d like to get rid of it, but no matter what I tried – I couldn’t concatenate two variables, I tried the following:

• ${container_name}_${log_type}
• “${container_name}_${log_type}”
• ${container_name}${log_type}

But in best case I see result label as if variables are empty (but they’re not).
In worst case fluentBit crashes due to config parsing error.

Is it possible to join two variables/keys in ‘labels’ field of Output section?