Add an OTLP (gRPC) logger to Envoy

[itamarkam]

Adding the OTLP logger will allow integration with more 3rd party monitoring frameworks, especially when using OT collector to convert them to whichever format needed.

Although OpenTelemetry logging isn't going to be part of the GA and the C++ SDK isn't ready yet, we don't actually need them in order to export OTLP logs - as long as the OTLP logs proto is stable.
The logs format is actually already available in the Amazon managed OT collector as an exporter, and Microsoft are also working on something similar, so it shouldn't change much - either way we'll get the OT community guarantee for backwards compatibility.

The general idea is to take the existing gRPC logger and just output a different format.

FYI @htuch @yanavlasov

[dio]

Seems like we need to also implement the client-side of collector service: https://github.com/open-telemetry/opentelemetry-proto/tree/master/opentelemetry/proto/collector/logs/v1 (gRPC and HTTP).

[htuch]

What is meant by "take the existing gRPC logger and just output a different format"? I think OTLP has a totally different gRPC service definition/endpoint as well as data model. I'd suggest making this a dedicated access logger built for OTLP that may borrow concepts (and potentially refactor) with gRPC access logger.

[itamarkam]

Some clarifications:

Seems like we need to also implement the client-side of collector service: https://github.com/open-telemetry/opentelemetry-proto/tree/master/opentelemetry/proto/collector/logs/v1 (gRPC and HTTP).

Yes, that's exactly what we need to do.

What is meant by "take the existing gRPC logger and just output a different format"? I think OTLP has a totally different gRPC service definition/endpoint as well as data model. I'd suggest making this a dedicated access logger built for OTLP that may borrow concepts (and potentially refactor) with gRPC access logger.

Yes, the idea is to create a dedicated access logger built for OTLP (i.e implements the client side of the collector service).
I was referring to the implementation details, which I understand how it can be unclear.

As for the implementation, we can re-use functionalities from existing loggers:

1. gRPC - the existing gRPC HTTP/TCP logger already takes care of streaming, batching etc. Basically I want to use all of this functionality, just with the OT service/protos. I'll start with the gRPC OT service, and if needed we can also implement the HTTP one.
2. Formatting - the existing File logger has a format config a string/JSON with placeholders to be filled with request/response data. As the OTLP logs are free form, we need the user to configure the output format. I think it's fairly straightforward to extend the string/JSON formatters to support protos as well. That is, the format configuration will be an OTLP log proto with placeholders.

These 2 orthogonal changes can be used to create the gRPC OTLP formattable logger.

The OTLP logger config would look something like this:
{
"common_config": "{...}" // CommonGrpcAccessLogConfig
"otlp_format": "{...}" // OTLP log proto with placeholders, similar to the File logger format config
}

[github-actions]

This issue has been automatically marked as stale because it has not had activity in the last 30 days. It will be closed in the next 7 days unless it is tagged "help wanted" or "no stalebot" or other activity occurs. Thank you for your contributions.

[itamarkam]

@yanavlasov @htuch Can we tag it with one of the above so it's not closed?

[itamarkam]

@envoyproxy/security-team @envoyproxy/dependency-shepherds

As part of this issue, I want to add dependencies on some protos from the OT repository

1. OpenTelemetry collector RPC service
2. OT logs proto
3. OT common proto

I'm following the dependency policy doc to get the required approvals.
OpenTelemetry is part of CNCF project, so it should comply with the policy.

Also, I'm not sure what goes into the api/.. dependencies and what goes to the regular one.

[htuch]

I think it's fine depending on a pure proto repository. The dependency policy largely applies to code that is linked into the data or observability planes, but API proto repos don't need to do things like have a security policy.

This belongs in api/bazel, since the API protos will be depending on it.