[exp/prometheusremotewrite] Exporting "target" instead of "target_info"

[gouthamve]

Describe the bug

When pushing data through Prometheus Remote Write, we should expose the Resource Attributes using the target_info metric, but we are currently pushing a target metric.

Steps to reproduce
Run a simple collector deployment with the following config:

exporters:
  prometheusremotewrite:
    endpoint: "http://prometheus:9090/api/v1/write"

processors:
  batch: {}
receivers:
  prometheus:
    config:
      global:
        scrape_interval: 5s
        external_labels:
          scraped_by: otel-collector 

      scrape_configs:
        - job_name: collector
          static_configs:
            - targets: ['localhost:8888']

service:
  pipelines:
    metrics:
      receivers: [prometheus]
      processors: [batch]
      exporters: [prometheusremotewrite]

What did you expect to see?
target_info in Prometheus.

What did you see instead?
target

What version did you use?
Version: v0.54.0

[povilasv]

Based on OTEL spec https://opentelemetry.io/docs/reference/specification/metrics/datamodel/#resource-attributes-1

I believe the metric should named target

Other resource attributes SHOULD be converted to a “target” info metric family, or MUST be dropped. The “target” info metric family is an info-typed metric family whose labels MUST include the resource attributes, and MUST NOT include any other labels other than job and instance

Note: the quotes around the word target

[gouthamve]

Yes, but Info type metrics should have an _info appended to them according to OpenMetrics spec: https://github.com/OpenObservability/OpenMetrics/blob/main/specification/OpenMetrics.md#info-1

[povilasv]

Agree, I believe we need to fix the otel spec first before merging your change

[gouthamve]

I think the OTEL Spec is correct already imo. The metric family for target_info is target.

Just that when exporting a metric called target of the info type in OpenMetrics, we should append _info to the end.

[codeboten]

@Aneurysm9 please take a look at this issue

[dashpole]

@gouthamve is correct. For other metric types (e.g. histograms), suffixes are appended when translating from pdata to PRW. For example, here we add _sum to the histogram sum sample. But since this series is manufactured from the resource, rather than from a pdata data point, it needs to handle type suffixing itself. So the OpenMetrics metric family name is target (as described in the spec), but the type suffix is _info, and is currently missing.

[github-actions]

This issue has been inactive for 60 days. It will be closed in 60 days if there is no activity. To ping code owners by adding a component label, see Adding Labels via Comments, or if you are unsure of which component this issue relates to, please ping @open-telemetry/collector-contrib-triagers. If this issue is still relevant, please ping the code owners or leave a comment explaining why it is still relevant. Otherwise, please close it.

Pinging code owners:

• exporter/prometheusremotewrite: @Aneurysm9

See Adding Labels via Comments if you do not have permissions to add labels yourself.

[dashpole]

This was fixed in #12086