Allow OTLP export with TLS enabled

[hertzsprung]

I'm running a Grafana agent that receives traffic over GRPC+TLS, but it seems krakend switches off TLS with no config option to reenable it.

krakend then fails with KRAKEND ERROR: [SERVICE: OpenTelemetry] failed to upload metrics: context deadline exceeded: rpc error: code = Unavailable desc = connection error: desc = "error reading server preface: http2: frame too large".

Could a config option be added to enable TLS with GRPC?

[Kavindu-Jayasinghe]

Hi! I faced a similar issue with sending metrics to Grafana. Instead of using gRPC with TLS directly, I set up Prometheus to export metrics from KrakenD, and it's working well for me.

Here’s the configuration I used in KrakenD for Prometheus:

"prometheus": [
  {
    "name": "metrics_export",
    "port": 9090, 
    "process_metrics": true,
    "go_metrics": true
  }
]

Prometheus scrapes the metrics from KrakenD, and then Grafana pulls them from Prometheus. This setup is working without any issues for me.