stacklok / toolhive / 18947711942

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github

Committed by web-flow

Commit Message

vMCP: Implement capability merging and routing integration (#2376)

* Implement Virtual MCP Server with capability merging and routing

This completes issue #154 by implementing the final stage of the
capability aggregation pipeline: exposing aggregated capabilities
via MCP protocol and routing requests to backends.

Components added:
- Router (pkg/vmcp/router/default_router.go): Thread-safe routing
  using RWMutex for capability name → backend target mapping.
  Supports dynamic routing table updates for future backend discovery.

- Virtual MCP Server (pkg/vmcp/server/server.go): Aggregates multiple
  backend MCP servers into unified interface. Uses mark3labs/mcp-go
  to expose tools/list, resources/list, prompts/list automatically.
  Routes incoming requests (tools/call, resources/read, prompts/get)
  to appropriate backends via Router.

Features:
- Automatic MCP protocol endpoint exposure
- Tool/resource/prompt routing with conflict-resolved names
- Request forwarding to backends via BackendClient
- Streamable HTTP transport support
- Graceful startup/shutdown

Testing:
- Router: 100% test coverage including concurrency tests
- Server: Unit tests for configuration, registration, error handling
- Integration tests: Full pipeline (Aggregator→Router→Server)
- All tests passing, linting clean

Architecture:
Client → Virtual MCP Server → Router → BackendClient → Backend MCPs
         (MCP protocol)        (routing) (HTTP)        (MCP servers)

Resolves: #154
Signed-off-by: Juan Antonio Osorio <ozz@stacklok.com>

* Address review feedback: timeouts and MIME type handling

Fix points 4 and 5 from review:

4. Extract magic number timeouts to constants:
   - Add defaultReadHeaderTimeout (10s) for HTTP server security
   - Add defaultShutdownTimeout (10s) for graceful shutdown
   - Replace hardcoded values with named constants

5. Fix hardcoded MIME type in resource handler:
   - Remove hardcoded "text/plain" MIME type
   - Look up actual MIME type from aggre... (continued)

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14 existing lines in 1 file now uncovered.

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