[ShryukGrandhi]

Why make this change?

Fixes #3759

runtime.telemetry.open-telemetry.exporter-protocol can be set to grpc or httpprotobuf in the config schema and through the CLI (--otel-protocol). The service ignored it: every OTLP exporter (logging in Program.cs, and logging, metrics and tracing in Startup.cs) hard-coded OtlpExportProtocol.Grpc. That means httpprotobuf never worked, and collectors that only accept OTLP/HTTP got nothing.

What is this change?

• Each OTLP exporter now uses the configured ExporterProtocol. If it isn't set, it still falls back to Grpc, so existing configs behave the same as before.

How was this tested?

• Integration Tests
• Unit Tests

Added TestOpenTelemetryExporterUsesHttpProtobufProtocol to OpenTelemetryTests. The test starts a local HttpListener as the OTLP endpoint, sets exporter-protocol to httpprotobuf and boots the service. It then emits a span on the DAB activity source and flushes the tracer provider, and asserts that the collector gets a request with Content-Type: application/x-protobuf. Without this change the test fails because no HTTP export arrives (the exporter speaks gRPC). With the change it passes. The existing OpenTelemetry tests still pass.

dotnet test src/Service.Tests/Azure.DataApiBuilder.Service.Tests.csproj --filter "FullyQualifiedName~OpenTelemetryTests"

Sample Request(s)

dab add-telemetry --otel-enabled true --otel-endpoint <collector-url> --otel-protocol httpprotobuf

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[Copilot]

🟡 Changes recommended

HTTP exports still need signal-specific endpoint handling, and the regression test can pass without verifying the intended trace.

2 open issues

• Verify TestActivity trace export before completing the test · New
• Resolve signal-specific OTLP/HTTP endpoint paths · New

What changed in this PR

This PR addresses #3759 by making DAB’s OpenTelemetry exporters honor the configured protocol instead of always using gRPC.

Changes:

• Apply ExporterProtocol to logging, metrics, and tracing exporters, retaining gRPC as the default.
• Add a local HTTP listener test intended to verify HTTP/protobuf trace export.

File	Description
src/​Service/​Startup.cs	Uses the configured protocol for logging, metrics, and tracing.
src/​Service/​Program.cs	Uses the configured protocol in the logging factory.
src/​Service.Tests/​Configuration/​Telemetry/​OpenTelemetryTests.cs	Adds an HTTP/protobuf export regression test.

_{Review effort: Balanced}