Hello @SinimaWath

Thanks for PR! When introducing Opentelemetry I wanted to avoid using additional opentelemetry configuration options in Centrifugo until really requred.

There is a OpenTelemetry Protocol Exporter spec which describes a way to specify exporter protocol: https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/protocol/exporter.md#specify-protocol

It describes OTEL_EXPORTER_OTLP_PROTOCOL env var and says that possible values are:

grpc for protobuf-encoded data using gRPC wire format over HTTP/2 connection
http/protobuf for protobuf-encoded data over HTTP connection
http/json for JSON-encoded data over HTTP connection

Looks like we now by default using http/protobuf which is fine. So I propose change this PR a bit to look for OTEL_EXPORTER_OTLP_PROTOCOL in Centrifugo to decide which exporter to use. If specified allow only http/protobuf and grpc values. I suppose there is no real reason to support http/json.

What do you think?

@FZambia Thanks, for the answer,

I think, using specification based ENV Variable is good idea, will implement that.

@FZambia Done, could you check please?

Amazing, many thanks @SinimaWath