Trying it out:
--------
package main
import (
"flag"
"log"
"net/http"
"github.com/prometheus/client_golang/prometheus"
"github.com/prometheus/client_golang/prometheus/promhttp"
)
var addr = flag.String("listen-address", ":8080", "The address to listen on
for HTTP requests.")
func main() {
metricName := "test_purposes"
help := "tests"
counter := prometheus.NewCounterVec(prometheus.CounterOpts{
Name: metricName,
Help: help,
}, []string{"status", "environment", "reason"})
prometheus.MustRegister(counter)
counter.WithLabelValues("success", "dev", "")
counter.WithLabelValues("error", "dev", "npe")
flag.Parse()
http.Handle("/metrics", promhttp.Handler())
log.Fatal(http.ListenAndServe(*addr, nil))
}
--------
Result:
# HELP test_purposes tests
# TYPE test_purposes counter
test_purposes{environment="dev",reason="",status="success"} 0
test_purposes{environment="dev",reason="npe",status="error"} 0
So, it does actually expose an empty value label - but prometheus should
treat that the same as the label not existing.
Personally, I'd much prefer that a given metric comes with a consistent set
of labels - and I think the API is trying to encourage that.
--------
counter.With(prometheus.Labels{"status": "success", "environment":
"dev"})
counter.With(prometheus.Labels{"status": "error", "environment":
"dev", "reason": "npe"})
--------
=> panic: inconsistent label cardinality: expected 3 label values but got 2
in prometheus.Labels{"environment":"dev", "status":"success"}
On Sunday, 26 June 2022 at 15:09:01 UTC+1 Brian Candler wrote:
> For any label you don't want, set the label value to empty string.
>
> On Sunday, 26 June 2022 at 14:47:20 UTC+1 [email protected] wrote:
>
>> Hi Brian,
>>
>> Thank you so much for your answer. I appreciate and agree with your
>> comments, for my use case using the second approach would be nice but using
>> the golang official lib https://github.com/prometheus/client_golang it's
>> not possible to create the same metric more than once even using different
>> labels.
>>
>> Thank you.
>>
>> Em sábado, 25 de junho de 2022 às 12:43:35 UTC-3, Brian Candler escreveu:
>>
>>> > But when the status is error I would like to add one more label:
>>> reason, to the same metric and it's not possible
>>>
>>> That's because it wouldn't be the same metric.
>>>
>>> In Prometheus, it's the metric name together with the complete set of
>>> labels which form the identity of a timeseries. If you add another label,
>>> then you've created a completely different timeseries.
>>>
>>> The normal way to handle this is to create separate counters (metrics)
>>> for each outcome:
>>>
>>> test_purposes{result="success",environment="dev"} 0
>>> test_purposes{result="npe",environment="dev"} 0
>>> test_purposes{result="oops",environment="dev"} 0
>>>
>>> Then you increment the appropriate one, depending on the result.
>>>
>>> You could also use your scheme:
>>>
>>> test_purposes{status="success",environment="dev"} 0
>>> test_purposes{status="error",reason="npe",environment="dev"} 0
>>> test_purposes{status="error",reason="oops",environment="dev"} 0
>>>
>>> Again you'd just create three counters as three separate metrics.
>>> Personally I find the first version easier to work with in queries, because
>>> it's easier to aggregate when the labels are consistent, but either way
>>> will work.
>>>
>>> On Saturday, 25 June 2022 at 15:41:04 UTC+1 [email protected] wrote:
>>>
>>>> Hi Guys,
>>>> I hope you are having a good weekend, I would like to have an
>>>> information about CounterVec, is there a way to dynamically add Labels
>>>> inside an already registered metric?
>>>>
>>>> For example:
>>>>
>>>> Creating a metric using two labels: status and environment
>>>> ```go
>>>> metricName := "test_purposes"
>>>> help := "tests"
>>>>
>>>> counter = promauto.NewCounterVec(prometheus.CounterOpts{
>>>> Name: metricName,
>>>> Help: help,
>>>> }, []string{"status", "environment"})
>>>>
>>>> counter.WithLabelValues("success", "dev")
>>>> ```
>>>>
>>>> But when the status is error I would like to add one more label:
>>>> reason, to the same metric and it's not possible
>>>>
>>>> ```go
>>>> counter = promauto.NewCounterVec(prometheus.CounterOpts{
>>>> Name: metricName,
>>>> Help: help,
>>>> }, []string{"status", "environment", "reason"})
>>>>
>>>> counter.WithLabelValues("success", "dev", "npe")
>>>> ```
>>>>
>>>> Just to explain why I need it, we're migrating an implementation of
>>>> datadog to prometheus and in the implementations based on datadog we have
>>>> a
>>>> lot of microservices sending metrics using different tags (labels) to the
>>>> same metric, if I could do the same using the prometheus lib it would be
>>>> great because we could only change the client without any modifications on
>>>> metric publishers.
>>>>
>>>
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