It's better to avoid honor_labels unless you really need it. It allows the
exporter to do bad things like overriding the "job" and "instance" labels.
Better to use metric_relabel_configs to relabel, at which point you have
the combined set of labels from service discovery and the scrape. A missing
label is the same as a label whose value is the empty string. So you can do
(untested):
metric_relabel_configs:
- source_labels: [ source, __address__ ]
regex: ";(.*)(:.*)?"
target_label: source
replacement: "${1}"
This works as long as the source label's value cannot start with a
semicolon - if it can, define a different "separator" character. If you
don't like that, another approach is to set a temporary label as a flag:
metric_relabel_configs:
- source_labels: [ source ]
regex: ""
target_label: __tmp_source_empty
replacement: Y
- source_labels: [ __tmp_source_empty, __address__ ]
regex: "Y;(.*)(:.*)?"
target_label: source
replacement: "${1}"
- target_label: __tmp_source_empty
replacement: ""
On Tuesday, 11 March 2025 at 17:39:58 UTC mohan garden wrote:
> Hi Everyone,
>
> I need to handle a scenario where I add a label to ingested metrics, but
> only if the label does not already exist in the collected data. If the
> label is present in a metric, it should remain unchanged.
>
> For example, given a set of metrics:
>
> custom_metrics_from_server{ source="server1.example.com",status="run" }
> 3213
> custom_metrics_from_server{ source="server1.example.com",status="pend" }
> 3215
>
> When additional metrics are collected from a node exporter, some will
> already have a "source=" label, while others will not:
>
> custom_metrics_from_server{ source="server1.example.com",status="run" }
> 3213
> custom_metrics_from_server{ source="server1.example.com",status="pend" }
> 3215
> node_cooling_device_max_state{name="7",type="Processor"} 0
>
> To ensure that all metrics contain the "source=" label without overriding
> existing ones, I figured the following approach using honor_labels and
> relabel_configs:
>
> honor_labels: true
> relabel_configs:
> - source_labels: [ _address_ ]
> regex: "(.*):(.*)"
> target_label: "source"
> replacement: '${1}'
>
> Is this the best way to handle this, or is there a more optimal approach?
> Please advice.
>
> Thanks!
>
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