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feat(contrib/mcp-go): Record MCP Session ID as tag #4106

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11 changes: 11 additions & 0 deletions contrib/mark3labs/mcp-go/mcpgo.go
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Original file line number Diff line number Diff line change
Expand Up @@ -53,6 +53,8 @@ func NewToolHandlerMiddleware() server.ToolHandlerMiddleware {
outputText = string(resultJSON)
}

tagWithSessionID(ctx, toolSpan)

toolSpan.AnnotateTextIO(string(inputJSON), outputText)

if err != nil {
Expand All @@ -75,6 +77,7 @@ func newHooks() *hooks {
func (h *hooks) onBeforeInitialize(ctx context.Context, id any, request *mcp.InitializeRequest) {
taskSpan, _ := llmobs.StartTaskSpan(ctx, "mcp.initialize", llmobs.WithIntegration("mark3labs/mcp-go"))
h.spanCache.Store(id, taskSpan)
tagWithSessionID(ctx, taskSpan)
}

func (h *hooks) onAfterInitialize(ctx context.Context, id any, request *mcp.InitializeRequest, result *mcp.InitializeResult) {
Expand All @@ -100,6 +103,14 @@ func (h *hooks) onError(ctx context.Context, id any, method mcp.MCPMethod, messa
span.Finish(llmobs.WithError(err))
}

func tagWithSessionID(ctx context.Context, span llmobs.Span) {
session := server.ClientSessionFromContext(ctx)
if session != nil {
sessionID := session.SessionID()
span.Annotate(llmobs.WithAnnotatedTags(map[string]string{"mcp_session_id": sessionID}))
}
}

func finishSpanWithIO[Req any, Res any](h *hooks, id any, request Req, result Res) {
value, ok := h.spanCache.LoadAndDelete(id)
if !ok {
Expand Down
40 changes: 36 additions & 4 deletions contrib/mark3labs/mcp-go/mcpgo_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -54,6 +54,11 @@ func TestIntegrationSessionInitialize(t *testing.T) {
server.WithHooks(hooks))

ctx := context.Background()
sessionID := "test-session-init"
session := &mockSession{id: sessionID}
session.Initialize()
ctx = srv.WithContext(ctx, session)

initRequest := `{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"protocolVersion":"2024-11-05","capabilities":{},"clientInfo":{"name":"test-client","version":"1.0.0"}}}`

response := srv.HandleMessage(ctx, []byte(initRequest))
Expand All @@ -76,6 +81,8 @@ func TestIntegrationSessionInitialize(t *testing.T) {
assert.Equal(t, "mcp.initialize", taskSpan.Name)
assert.Equal(t, "task", taskSpan.Meta["span.kind"])

assert.Contains(t, taskSpan.Tags, "mcp_session_id:test-session-init")

assert.Contains(t, taskSpan.Meta, "input")
assert.Contains(t, taskSpan.Meta, "output")

Expand All @@ -99,7 +106,11 @@ func TestIntegrationToolCallSuccess(t *testing.T) {
tt := testTracer(t)
defer tt.Stop()

hooks := &server.Hooks{}
AddServerHooks(hooks)

srv := server.NewMCPServer("test-server", "1.0.0",
server.WithHooks(hooks),
server.WithToolHandlerMiddleware(NewToolHandlerMiddleware()))

calcTool := mcp.NewTool("calculator",
Expand Down Expand Up @@ -131,9 +142,13 @@ func TestIntegrationToolCallSuccess(t *testing.T) {
session.Initialize()
ctx = srv.WithContext(ctx, session)

initRequest := `{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"protocolVersion":"2024-11-05","capabilities":{},"clientInfo":{"name":"test-client","version":"1.0.0"}}}`
response := srv.HandleMessage(ctx, []byte(initRequest))
assert.NotNil(t, response)

toolCallRequest := `{"jsonrpc":"2.0","id":2,"method":"tools/call","params":{"name":"calculator","arguments":{"operation":"add","x":5,"y":3}}}`

response := srv.HandleMessage(ctx, []byte(toolCallRequest))
response = srv.HandleMessage(ctx, []byte(toolCallRequest))
assert.NotNil(t, response)

responseBytes, err := json.Marshal(response)
Expand All @@ -145,10 +160,25 @@ func TestIntegrationToolCallSuccess(t *testing.T) {
assert.Equal(t, "2.0", resp["jsonrpc"])
assert.NotNil(t, resp["result"])

spans := tt.WaitForLLMObsSpans(t, 1)
require.Len(t, spans, 1)
spans := tt.WaitForLLMObsSpans(t, 2)
require.Len(t, spans, 2)

var initSpan, toolSpan *testtracer.LLMObsSpan
for i := range spans {
if spans[i].Name == "mcp.initialize" {
initSpan = &spans[i]
} else if spans[i].Name == "calculator" {
toolSpan = &spans[i]
}
}

require.NotNil(t, initSpan, "initialize span not found")
require.NotNil(t, toolSpan, "tool span not found")

expectedTag := "mcp_session_id:test-session-123"
assert.Contains(t, initSpan.Tags, expectedTag)
assert.Contains(t, toolSpan.Tags, expectedTag)

toolSpan := spans[0]
assert.Equal(t, "calculator", toolSpan.Name)
assert.Equal(t, "tool", toolSpan.Meta["span.kind"])

Expand Down Expand Up @@ -215,6 +245,8 @@ func TestIntegrationToolCallError(t *testing.T) {
assert.Equal(t, "error_tool", toolSpan.Name)
assert.Equal(t, "tool", toolSpan.Meta["span.kind"])

assert.Contains(t, toolSpan.Tags, "mcp_session_id:test-session-456")

assert.Contains(t, toolSpan.Meta, "error.message")
assert.Contains(t, toolSpan.Meta["error.message"], "intentional test error")
assert.Contains(t, toolSpan.Meta, "error.type")
Expand Down
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