How to rename label within a metric in Prometheus - monitoring

Question

I have a query:
node_systemd_unit_state{instance="server-01",job="node-exporters",name="kubelet.service",state="active"} 1
I want the label name being renamed (or replaced) to unit_name ONLY within the node_systemd_unit_state metric. So, desired result is:
node_systemd_unit_state{instance="server-01",job="node-exporters",unit_name="kubelet.service",state="active"} 1
There are many other metrics with a label name name in the node-exporters job. That's why I can't use relabel config across the job.

Answer 1

you can use the label_replace function in promQL, but it also add the label, don't replace it
label_replace(
<vector_expr>, "<desired_label>", "$1", "<existing_label>", "(.+)"
)
label_replace(
node_systemd_unit_state{instance="server-01",job="node-exporters",name="kubelet.service",state="active"},
"unit_name","$1","name", "(.+)"
)
So, to avoid the repetition you can add:
sum(label_replace(
node_systemd_unit_state{instance="server-01",job="node-exporters",name="kubelet.service",state="active"},
"unit_name","$1","name", "(.+)"
)
)by(unit_name)

Answer 2

I got tired of all the fragmented documentation and I feel I provided a better answer in this post here:
https://medium.com/#texasdave2/replace-and-remove-a-label-in-a-prometheus-query-9500faa302f0
Replace is not a true REPLACE
Your goal is to simply replace the old label name “old_job_id” with a new label name “new_task_id”. Prometheus label_replace will really “add” the new label name. It will preserve the old label name as well… So, that could be a problem, it’s not a true “replace in place”.
So if you want to “add” your new label name and “remove” the old label name, you need to do this:
sum without (old_job_id) (label_replace(metric, "new_task_id", "$1", "old_job_id", "(.*)"))
Here’s how this reads:
sum without (old_job_id) will remove the old label name from the
query output
metric is your metric, like “node_filesystem_avail_bytes”
“new_task_id” is where you would put your new label name
“$1” is regex for using the string in new label name, don’t change
this
“old_job_id” is where you’ll put your old label, the one you want to
get rid of (.*……. that mess is regex that will replace the whole
label name

Answer 3

You can have more than one source label, so:
- source_labels: [__name__, name]
regex: "node_systemd_unit_state;(.+)"
target_label: unit_name
If the label name isn't matching up with other metrics/exporters, you should file a bug with them. Relabelling like this should only be a temporary solution while a proper fix is being pursued.

Answer 4

Prometheus allows renaming labels in the following places:
During metric scrape. In this case you need to add the following relabeling rules into metric_relabel_configs section at the corresponding scrape_config:
metric_relabel_configs:
- source_labels: [__name__, name]
regex: "node_systemd_unit_state;(.+)"
target_label: unit_name
- source_labels: [__name__, name]
regex: "node_systemd_unit_state;(.+)"
target_label: name
replacement: ""
The first rule copies name label value into unit_name label for metrics with node_systemd_unit_state name. The second rule sets name label value to an empty string (e.g. deletes the name label) for metrics with node_systemd_unit_state name.
During querying via label_join() function:
label_join(
label_join(node_systemd_unit_state, "unit_name", "", "name"),
"name", "", "non_existing_label"
)
The inner label_join() copies name label into unit_name label. The outer label_join() substitutes the original name label with an empty string (e.g. remove the name label).
As you can see, label_join() isn't the best function for label renaming. The label_replace() isn't the best function for label renaming too. While Prometheus doesn't provide better solutions for label renaming, such solution exist in Prometheus-like systems such as VictoriaMetrics (I'm the author of this system). It provides label_move() function:
label_move(node_systemd_unit_state, "name", "unit_name")
Additionally, VictoriaMetrics provides if option for conditional relabeling rules. For example, the following relabeling rules are equivalent to the rules above, but are easier to understand and maintain:
metric_relabel_configs:
- if: 'node_systemd_unit_state{name!=""}'
source_labels: [name]
target_label: unit_name
- if: 'node_systemd_unit_state{name!=""}'
target_label: name
replacement: ""

Answer 5

https://demo.promlens.com/?q=label_replace(up%2C%20%22hostname%22%2C%20%22%241%22%2C%20%22instance%22%2C%20%22(.%2B)%3A(%5C%5Cd%2B)%22)
Assume you have metric namely up
up{instance="cadvisor:8080", job="cadvisor"}
up{instance="demo-service-0:10000", job="demo"}
up{instance="demo-service-1:10001", job="demo"}
up{instance="demo-service-2:10002", job="demo"}
up{instance="docker-hub-exporter:9170", job="docker-hub-exporter"}
up{instance="node-exporter:9100", job="node"}
up{instance="prometheus:9090", job="prometheus"}
Now query
label_replace(up, "hostname", "$1", "instance", "(.+)-(.+)-(\\d+):(\\d+)")
will return with new label hostname with first match group ("$1").
up{instance="cadvisor:8080", job="cadvisor"}
up{hostname="demo", instance="demo-service-0:10000", job="demo"}
up{hostname="demo", instance="demo-service-1:10001", job="demo"}
up{hostname="demo", instance="demo-service-2:10002", job="demo"}
up{instance="docker-hub-exporter:9170", job="docker-hub-exporter"}
up{instance="node-exporter:9100", job="node"}
up{instance="prometheus:9090", job="prometheus"}
Query
label_replace(up, "hostname", "$2", "instance", "(.+)-(.+)-(\\d+):(\\d+)")
will return with new label hostname with second match group ("$2") of the regEx.
up{instance="cadvisor:8080", job="cadvisor"}
up{hostname="service", instance="demo-service-0:10000", job="demo"}
up{hostname="service", instance="demo-service-1:10001", job="demo"}
up{hostname="service", instance="demo-service-2:10002", job="demo"}
up{instance="docker-hub-exporter:9170", job="docker-hub-exporter"}
up{instance="node-exporter:9100", job="node"}
up{instance="prometheus:9090", job="prometheus"}