receiver/prometheus: Metric adjuster sets start time incorrectly when honor_labels==true

[ridwanmsharif]

Component(s)

receiver/prometheus

What happened?

Description

When honor_labels is set to true - the metrics could override the job and instance labels. But the metrics adjuster assumes that all the metrics from a single scrape share the same job and instance which isn't true.

https://github.com/open-telemetry/opentelemetry-collector-contrib/blob/15ddc2998deabb640f904d6ed812bf89f43ab957/receiver/prometheusreceiver/internal/metrics_adjuster.go#L260-L265

Acceptance Criteria: validate and test against this assumption. Or add assertion that all metrics must come from the same resource if that is intended.

Collector version

all versions of contrib

Environment information

Environment

OS: (e.g., "Ubuntu 20.04") Compiler(if manually compiled): (e.g., "go 14.2")

OpenTelemetry Collector configuration

No response

Log output

No response

Additional context

No response

[github-actions[bot]]

Pinging code owners:

• receiver/prometheus: @Aneurysm9 @dashpole

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