Target Allocator relabel filter incorrectly drops targets based on seeded labels

[swiatekm]

Component(s)

No response

What happened?

Description

When keeping or dropping labels based on seeded labels, target allocator may do the wrong thing. For example:

scrape_configs:
  # keep on `job`: Prometheus keeps (job is seeded), allocator drops -> silent loss.
  - job_name: gap-keep-on-job
    static_configs:
      - targets: ['10.20.0.1:9100']
    relabel_configs:
      - {source_labels: [job], regex: 'gap-keep-on-job', action: keep}

Same is true for other seeded labels like __scheme__.

Steps to Reproduce

See: #5244.

Expected Result

Target Allocator's keep/drop behavior should be consistent with Prometheus.

Actual Result

The target mentioned above is dropped by target allocator but kept by prometheus.

Kubernetes Version

all supported

Operator version

main

Collector version

v0.153.0

Environment information

Log output

Additional context

No response

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