prometheus receiver: more info about scrape error

[morigs]

Is your feature request related to a problem? Please describe.
Currently, prometheusreceiver in case of error reports the following in the logs:

warn    internal/metricsbuilder.go:124  Failed to scrape Prometheus endpoint    {"kind": "receiver", "name": "prometheus", "scrape_timestamp": 1639773267689, "target_labels": "map[__name__:up]"}

It would be awesome to have more information about what really went wrong for debugging purposes.

Describe the solution you'd like
Perhaps it's possible to log http request errors. For example, socket hang up, timeout exceeded or response code 503.

[jpkrohling]

cc @Aneurysm9 @dashpole

[dashpole]

See open-telemetry/opentelemetry-collector#2364 (comment). Scraping happens in the prometheus server code, and is a debug log line. You can enable debug logging with --log-level=DEBUG

[morigs]

@dashpole Thank you!
It's kinda strange that error is on the debug level

[jinxin-fu]

See open-telemetry/opentelemetry-collector#2364 (comment). Scraping happens in the prometheus server code, and is a debug log line. You can enable debug logging with --log-level=DEBUG

Hi. I am a green hand in this project . I want to ask where to add the debug logging flag --log-level=DEBUG for image "otel/opentelemetry-collector-contrib". Looking forward to your reply Thanks.

[morigs]

@jinxin-fu usually, you specify arguments after image name, if you use docker. For exanple,

$ docker run -p 4317:4317 -it --rm -v $(pwd)/otel:/otel --name otel \
  otel/opentelemetry-collector-contrib:0.42.0 --config /otel/config.yaml --log-level=DEBUG

However, it looks like --log-level flag has been deprecated and removed in v0.38.0

From now on you should use config file instead. Use service.telemetry.logs.level

receivers:
  otlp:
    protocols:
      grpc:
      http:

processors:
  batch:

exporters:
  jaeger:
    endpoint: "host.docker.internal:14250"
    tls:
      insecure: true

service:
  telemetry:
    logs:
      level: DEBUG
  extensions: []
  pipelines:
    traces:
      receivers: [otlp]
      processors: [batch]
      exporters: [jaeger]

[jinxin-fu]

Thanks, I have change the otel-collector-conf with and works normally:

service:
  telemetry:
    logs:
      level: "debug"