[Helidon 4 SE] Metrics format not compatible with Prometheus: data does not end with # EOF

[dili91]

Environment Details

• Helidon Version: 4
• Helidon SE
• JDK version: 21
• OS: macOs Ventura 13.6.1
• Docker version: 20.10.17
• Prometheus version (Docker): prom/prometheus:v2.4.72

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Problem Description

I'm not able to configure Prometheus to ingest the metrics exposed at the /observe/metrics endpoint as described in this guide.
The error I'm getting on Prometheus when trying to scrape the endpoint is data does not end with # EOF, which seems similar to what is described on issue #4884 for Helidon 2.x and 3.x.

Steps to reproduce

• Follow this guide and register the default metrics.
• Spin up a Prometheus docker container and add the /observe/metrics endpoint as target.
• Check the target status on ${prometheusHost:Port}/targets