Add new profile signal (open-telemetry#534)

This is a follow up to [OTEP 239: Introduces Profiling Data Model v2](open-telemetry/oteps#239)

The main motivation behind this PR is that this will allow us to start experimenting with the profiles proto in opentelemetry-collector. I marked the profiles part as `Experimental` to indicate that this is not a final version of the data model.

I copied the proto from the OTEP, and moved `pprofextended.proto` from `profiles/v1/alternatives/pprofextended.proto` to just `profiles/v1/pprofextended.proto`. I did this because I figured we no longer have alternative representations and this will reduce confusion for people outside of Profiling SIG. The rest of the proto stayed the same.

I tested this file with a collector fork and I it compiles properly.

README.md

@@ -51,6 +51,7 @@ components as indicated by the Maturity table below.
 | metrics/\*<br>collector/metrics/* | Stable | [Stable](docs/specification.md#json-protobuf-encoding) |
 | trace/\*<br>collector/trace/* | Stable | [Stable](docs/specification.md#json-protobuf-encoding) |
 | logs/\*<br>collector/logs/* | Stable | [Stable](docs/specification.md#json-protobuf-encoding) |
+| profiles/\*<br>collector/profiles/* | Experimental | [Experimental](docs/specification.md#json-protobuf-encoding) |
 
 (See [maturity-matrix.yaml](https://github.com/open-telemetry/community/blob/47813530864b9fe5a5146f466a58bd2bb94edc72/maturity-matrix.yaml#L57)
 for definition of maturity levels).

opentelemetry/proto/collector/profiles/v1experimental/profiles_service.proto

@@ -0,0 +1,78 @@
+// Copyright 2023, OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+syntax = "proto3";
+
+package opentelemetry.proto.collector.profiles.v1experimental;
+
+import "opentelemetry/proto/profiles/v1experimental/profiles.proto";
+
+option csharp_namespace = "OpenTelemetry.Proto.Collector.Profiles.V1Experimental";
+option java_multiple_files = true;
+option java_package = "io.opentelemetry.proto.collector.profiles.v1experimental";
+option java_outer_classname = "ProfilesServiceProto";
+option go_package = "go.opentelemetry.io/proto/otlp/collector/profiles/v1experimental";
+
+// Service that can be used to push profiles between one Application instrumented with
+// OpenTelemetry and a collector, or between a collector and a central collector.
+service ProfilesService {
+  // For performance reasons, it is recommended to keep this RPC
+  // alive for the entire life of the application.
+  rpc Export(ExportProfilesServiceRequest) returns (ExportProfilesServiceResponse) {}
+}
+
+message ExportProfilesServiceRequest {
+  // An array of ResourceProfiles.
+  // For data coming from a single resource this array will typically contain one
+  // element. Intermediary nodes (such as OpenTelemetry Collector) that receive
+  // data from multiple origins typically batch the data before forwarding further and
+  // in that case this array will contain multiple elements.
+  repeated opentelemetry.proto.profiles.v1experimental.ResourceProfiles resource_profiles = 1;
+}
+
+message ExportProfilesServiceResponse {
+  // The details of a partially successful export request.
+  //
+  // If the request is only partially accepted
+  // (i.e. when the server accepts only parts of the data and rejects the rest)
+  // the server MUST initialize the `partial_success` field and MUST
+  // set the `rejected_<signal>` with the number of items it rejected.
+  //
+  // Servers MAY also make use of the `partial_success` field to convey
+  // warnings/suggestions to senders even when the request was fully accepted.
+  // In such cases, the `rejected_<signal>` MUST have a value of `0` and
+  // the `error_message` MUST be non-empty.
+  //
+  // A `partial_success` message with an empty value (rejected_<signal> = 0 and
+  // `error_message` = "") is equivalent to it not being set/present. Senders
+  // SHOULD interpret it the same way as in the full success case.
+  ExportProfilesPartialSuccess partial_success = 1;
+}
+
+message ExportProfilesPartialSuccess {
+  // The number of rejected profiles.
+  //
+  // A `rejected_<signal>` field holding a `0` value indicates that the
+  // request was fully accepted.
+  int64 rejected_profiles = 1;
+
+  // A developer-facing human-readable message in English. It should be used
+  // either to explain why the server rejected parts of the data during a partial
+  // success or to convey warnings/suggestions during a full success. The message
+  // should offer guidance on how users can address such issues.
+  //
+  // error_message is an optional field. An error_message with an empty value
+  // is equivalent to it not being set.
+  string error_message = 2;
+}

opentelemetry/proto/collector/profiles/v1experimental/profiles_service_http.yaml

@@ -0,0 +1,9 @@
+# This is an API configuration to generate an HTTP/JSON -> gRPC gateway for the
+# OpenTelemetry service using github.com/grpc-ecosystem/grpc-gateway.
+type: google.api.Service
+config_version: 3
+http:
+ rules:
+ - selector: opentelemetry.proto.collector.profiles.v1.ProfilesService.Export
+   post: /v1experimental/profiles
+   body: "*"