add label from one metrics to matching label to other metrics

[sunils...@gmail.com]

Hi 

I have to label from one metrics to remaining other metrics .  Can we do it using relabel_config in pometheus.yml.

Example : 

Below metrics holds topic and source label :

source_topic_metrics(topic=topic1, source=source1)

source_topic_metrics(topic=topic2, source=source2)

Other metrics holds details like : 

fluentd_input_rate(topic=topic1, host=host1)

fluentd_input_rate(topic=topic2, host=host1)

kafka_log_size(topic=topic1)

kafka_log_size(topic=topic2)

I want to add labels from above query and want output as :

fluentd_input_rate(topic=topic1, host=host1, source=source1)

fluentd_input_rate(topic=topic2, host=host1, source=source2)

kafka_log_size(topic=topic1, source=source1)

kafka_log_size(topic=topic2 source=source2)

So here , common match is topic, based on this label match I want to add source label in each metrics . 

Thanks

Sunil Sagar

[Brian Candler]

You can only use relabel_config if you know prior to each scrape the extra labels you want to add.

If you want to combine labels from two different metrics, then create a PromQL query that does the join, and when you have that working, put it into a recording rule.  You can find examples of the join here:

https://www.robustperception.io/how-to-have-labels-for-machine-roles

https://www.robustperception.io/exposing-the-software-version-to-prometheus

https://www.robustperception.io/left-joins-in-promql

https://prometheus.io/docs/prometheus/latest/querying/operators/#many-to-one-and-one-to-many-vector-matches