Add support for OTLP/JSON

[JamesNK]

Description

PR adds support for receiving OTLP/JSON data. This data follows the spec at https://protobuf.dev/programming-guides/json/ and https://opentelemetry.io/docs/specs/otlp/#json-protobuf-encoding

The implementation adds new C# types, deserializes to them, then creates types generated from Protobuf. All logic from that point on only works with the Protobuf types.

It doesn't use gRPC JSON transcoding for a couple of reasons:

• There are some differences between gRPC JSON transcoding and what OTLP uses (notably, traceId and spanId fields are hex instead of base64)
• The JSON types here will eventually be reused for more features:
  • Export telemetry button in the dashboard to download telemetry as JSON
  • API to get telemetry from the dashboard
  • Getting telemetry from the dashboard using the CLI (don't want to force the CLI to have a dependency on Goolge.Protobuf)

Fixes #6947

Checklist

• Is this feature complete?
  • Yes. Ready to ship.
  • No. Follow-up changes expected.
• Are you including unit tests for the changes and scenario tests if relevant?
  • Yes
  • No
• Did you add public API?
  • Yes
    • If yes, did you have an API Review for it?
      • Yes
      • No
    • Did you add <remarks /> and <code /> elements on your triple slash comments?
      • Yes
      • No
  • No
• Does the change make any security assumptions or guarantees?
  • Yes
    • If yes, have you done a threat model and had a security review?
      • Yes
      • No
  • No
• Does the change require an update in our Aspire docs?
  • Yes
    • Link to aspire-docs issue (consider using one of the following templates):
      • New (or update) doc-idea template
      • New breaking-change template
      • New diagnostic template
  • No

[github-actions]

🚀 Dogfood this PR with:

⚠️ WARNING: Do not do this without first carefully reviewing the code of this PR to satisfy yourself it is safe.

curl -fsSL https://raw.githubusercontent.com/dotnet/aspire/main/eng/scripts/get-aspire-cli-pr.sh | bash -s -- 13557

Or

• Run remotely in PowerShell:

iex "& { $(irm https://raw.githubusercontent.com/dotnet/aspire/main/eng/scripts/get-aspire-cli-pr.ps1) } 13557"

[Copilot]

Pull request overview

This PR adds support for receiving OTLP telemetry data in JSON format (application/json) in addition to the existing Protobuf format (application/x-protobuf). The implementation deserializes JSON to custom C# types, then converts them to Protobuf types for processing through the existing pipeline.

Key changes:

• Created JSON representation types for OTLP traces, logs, metrics, and common structures
• Implemented bidirectional converters between JSON and Protobuf formats
• Updated HTTP endpoints to accept and respond with JSON based on content-type negotiation
• Added comprehensive integration tests covering all telemetry signal types

Reviewed changes

Copilot reviewed 18 out of 18 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
tests/Aspire.Dashboard.Tests/Integration/OtlpHttpServiceTests.cs	Updated unsupported content type tests from application/json to application/xml now that JSON is supported
tests/Aspire.Dashboard.Tests/Integration/OtlpHttpJsonTests.cs	New comprehensive test suite with 9 tests validating JSON format for traces, logs, events, metrics, auth, and error handling
src/Aspire.Dashboard/Otlp/opentelemetry/proto/trace/v1/trace.proto	Updated to OTLP spec v1.9.0 - added flags field, SpanFlags enum, enhanced documentation
src/Aspire.Dashboard/Otlp/opentelemetry/proto/resource/v1/resource.proto	Added entity_refs field and improved documentation per spec updates
src/Aspire.Dashboard/Otlp/opentelemetry/proto/metrics/v1/metrics.proto	Added metadata field, enhanced documentation, corrected URLs from OpenObservability to prometheus organization
src/Aspire.Dashboard/Otlp/opentelemetry/proto/logs/v1/logs.proto	Added event_name field for event logs, enhanced documentation per spec updates
src/Aspire.Dashboard/Otlp/opentelemetry/proto/common/v1/common.proto	Added EntityRef message type, improved documentation for all common types
src/Aspire.Dashboard/Otlp/opentelemetry/proto/collector//*_service.proto	Removed outdated RPC lifecycle comments from service definitions
src/Aspire.Dashboard/Otlp/Model/Serialization/OtlpTraceJson.cs	New file defining JSON types for trace data with proper serialization attributes
src/Aspire.Dashboard/Otlp/Model/Serialization/OtlpResourceJson.cs	New file defining JSON types for resource data
src/Aspire.Dashboard/Otlp/Model/Serialization/OtlpMetricsJson.cs	New file defining JSON types for metrics data (631 lines)
src/Aspire.Dashboard/Otlp/Model/Serialization/OtlpLogsJson.cs	New file defining JSON types for logs/events data
src/Aspire.Dashboard/Otlp/Model/Serialization/OtlpCommonJson.cs	New file defining shared JSON types (AnyValue, KeyValue, InstrumentationScope, EntityRef)
src/Aspire.Dashboard/Otlp/Model/Serialization/OtlpJsonSerializerContext.cs	Source-generated JSON serializer context for AOT compatibility
src/Aspire.Dashboard/Otlp/Model/Serialization/OtlpJsonProtobufConverter.cs	Bidirectional conversion logic between JSON and Protobuf formats (929 lines)
src/Aspire.Dashboard/Otlp/Http/OtlpHttpEndpointsBuilder.cs	Enhanced to handle JSON content-type, deserialize JSON requests, serialize JSON responses

[davidfowl]

Where's the playground sample that uses this?

[JamesNK]

BrowserTelemetry app now uses OTLP/JSON. Add it can be configured using WithOtlpExporter