[extension/healthcheckv2] Add partial gRPC service implementation (#3…

…4028)

**Description:** <Describe what has changed.>
The PR is the fourth in a series to decompose #30673 into more
manageable pieces for review. This PR introduces the basic structure for
the gRPC health check service, which is an implementation of the
[grpc_health_v1
service](https://github.com/grpc/grpc-proto/blob/master/grpc/health/v1/health.proto).
This PR implements the unary `Check` RPC. In order minimize PR size, the
streaming `Watch` RPC will be introduced in a followup.

**Link to tracking Issue:** #26661

**Testing:** Units / manual

**Documentation:** Comments, etc.

.chloggen/healthcheckv2-grpc-check.yaml

@@ -0,0 +1,27 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: 'enhancement'
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: 'healthcheckv2extension'
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Add partial gRPC service implementation to healthcheckv2.
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [26661]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:
+
+# If your change doesn't affect end users or the exported elements of any package,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: []

extension/healthcheckv2extension/go.mod

@@ -16,6 +16,7 @@ require (
 	go.opentelemetry.io/otel/trace v1.28.0
 	go.uber.org/goleak v1.3.0
 	go.uber.org/zap v1.27.0
+	google.golang.org/grpc v1.65.0
 )
 
 require (
@@ -66,7 +67,6 @@ require (
 	golang.org/x/sys v0.21.0 // indirect
 	golang.org/x/text v0.16.0 // indirect
 	google.golang.org/genproto/googleapis/rpc v0.0.0-20240701130421-f6361c86f094 // indirect
-	google.golang.org/grpc v1.65.0 // indirect
 	google.golang.org/protobuf v1.34.2 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 )

extension/healthcheckv2extension/internal/grpc/grpc.go

@@ -0,0 +1,61 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package grpc // import "github.com/open-telemetry/opentelemetry-collector-contrib/extension/healthcheckv2extension/internal/grpc"
+
+import (
+	"context"
+	"time"
+
+	"go.opentelemetry.io/collector/component"
+	"google.golang.org/grpc/codes"
+	healthpb "google.golang.org/grpc/health/grpc_health_v1"
+	grpcstatus "google.golang.org/grpc/status"
+
+	"github.com/open-telemetry/opentelemetry-collector-contrib/extension/healthcheckv2extension/internal/status"
+)
+
+var (
+	errNotFound = grpcstatus.Error(codes.NotFound, "Service not found.")
+
+	statusToServingStatusMap = map[component.Status]healthpb.HealthCheckResponse_ServingStatus{
+		component.StatusNone:             healthpb.HealthCheckResponse_NOT_SERVING,
+		component.StatusStarting:         healthpb.HealthCheckResponse_NOT_SERVING,
+		component.StatusOK:               healthpb.HealthCheckResponse_SERVING,
+		component.StatusRecoverableError: healthpb.HealthCheckResponse_SERVING,
+		component.StatusPermanentError:   healthpb.HealthCheckResponse_SERVING,
+		component.StatusFatalError:       healthpb.HealthCheckResponse_NOT_SERVING,
+		component.StatusStopping:         healthpb.HealthCheckResponse_NOT_SERVING,
+		component.StatusStopped:          healthpb.HealthCheckResponse_NOT_SERVING,
+	}
+)
+
+func (s *Server) Check(
+	_ context.Context,
+	req *healthpb.HealthCheckRequest,
+) (*healthpb.HealthCheckResponse, error) {
+	st, ok := s.aggregator.AggregateStatus(status.Scope(req.Service), status.Concise)
+	if !ok {
+		return nil, errNotFound
+	}
+
+	return &healthpb.HealthCheckResponse{
+		Status: s.toServingStatus(st.Event),
+	}, nil
+}
+
+func (s *Server) toServingStatus(
+	ev status.Event,
+) healthpb.HealthCheckResponse_ServingStatus {
+	if s.componentHealthConfig.IncludeRecoverable &&
+		ev.Status() == component.StatusRecoverableError &&
+		time.Now().After(ev.Timestamp().Add(s.componentHealthConfig.RecoveryDuration)) {
+		return healthpb.HealthCheckResponse_NOT_SERVING
+	}
+
+	if s.componentHealthConfig.IncludePermanent && ev.Status() == component.StatusPermanentError {
+		return healthpb.HealthCheckResponse_NOT_SERVING
+	}
+
+	return statusToServingStatusMap[ev.Status()]
+}