Feat/telemetry http exporter (#314)

* feat(telemetry): add OTLP HTTP exporter and print TraceID

- Add HTTP/protobuf exporter support alongside existing gRPC exporter
- Route based on OTEL_EXPORTER_OTLP_PROTOCOL config (http/protobuf vs grpc)
- Print TraceID to stderr when telemetry is enabled for easier correlation
- Add corresponding unit tests

* feat(telemetry): add span coverage for LLM calls, tool execution, plan/filter phases

- Add StartLLMSpan / RecordLLMResult helpers (span.go), symmetric with
  existing StartToolSpan / RecordToolResult
- Wrap LLM completion calls in llmloop.RunPerFile with llm.request spans
- Wrap all three tool execution paths in executeToolCall with
  tool.execute.* spans (dynamic tools, code_comment sync/async, other tools)
- Add plan.execute span around executePlanPhase
- Add main.loop span around RunPerFile call in executeSubtask
- Add review_filter.execute span around executeReviewFilter, with
  comments.before / comments.filtered attributes
- Record llm.error attribute on LLM failures for diagnosability
- Record review.repo / review.from / review.to / review.model on the
  top-level review.run span
- Metrics (RecordLLMRequest / RecordToolCall) are preserved alongside
  the new spans — they serve different purposes (aggregate dashboards
  vs per-run diagnosis)

Verified end-to-end against Sunfire (OTLP HTTP gateway): full span tree
observed for review.run -> subtask.execute -> plan.execute/main.loop/
review_filter.execute -> llm.request/tool.execute.*

* fix(telemetry): address CR findings — span error handling, async span lifecycle, protocol robustness

- Add span.RecordError(err) to RecordLLMResult and RecordToolResult for
  consistency with EndSpan
- Use OTel standard pattern (span.SetStatus + span.RecordError) in error
  paths of review.run, plan.execute, main.loop, review_filter.execute
- Move async code_comment span end into pool.Submit callback so span
  duration reflects actual execution time
- Unify time.Since(startTime) in code_comment error path to a single dur
- Remove http/json from supported OTLP protocols (not actually implemented)
- Add stderr warning when unknown OTLP protocol falls back to gRPC

* feat(telemetry): include trace_id in JSON output, restrict stderr to text format

- Add trace_id as top-level field in jsonOutput struct (omitempty)
- JSON format: trace_id in structured response for programmatic extraction
- Text format: TraceID printed to stderr for human debugging
- Telemetry disabled: trace_id field omitted entirely

* fix: address PR review findings

- loop.go: wrap async span lifecycle in defer to prevent leak on panic
- exporter.go: update parseOTLPEndpoint comment to reflect gRPC+HTTP usage
- scan_cmd.go: align traceID extraction and OTel error handling with review_cmd
- output.go/shared.go: propagate traceID to outputJSONNoFiles for consistency
- agent.go: move comments.filtered attribute before early return so 0 is
  distinguishable from not-executed

* feat(telemetry): address PR review — http/json routing, LLM span coverage, trace_id tests

- Route http/json to HTTP exporter (Go OTel SDK HTTP transport only
  supports protobuf serialization; users need HTTP transport, not JSON encoding)
- Add llm.request spans to executePlanPhase, executeReviewFilter, and
  ReLocateComment with Usage nil-safety consistent with loop.go
- Add trace_id assertions to output helper tests and emitRunResult
  end-to-end tests using real TracerProvider

* docs: add OTLP protocol selection and endpoint format to telemetry section

Sync across all 5 README language versions (en, zh-CN, ja-JP, ko-KR, ru-RU).

* fix: unify time.Since in async code_comment defer to single dur variable

cmd/opencodereview/emit_run_result_test.go

@@ -7,6 +7,9 @@ import (
 	"testing"
 	"time"
 
+	"go.opentelemetry.io/otel"
+	sdktrace "go.opentelemetry.io/otel/sdk/trace"
+
 	"github.com/open-code-review/open-code-review/internal/agent"
 	"github.com/open-code-review/open-code-review/internal/model"
 )
@@ -175,3 +178,61 @@ func TestEmitRunResult_NilQuietHandle(t *testing.T) {
 	})
 	_ = got
 }
+
+func TestEmitRunResult_JSONTraceIDFromContext(t *testing.T) {
+	tp := sdktrace.NewTracerProvider()
+	defer tp.Shutdown(context.Background())
+	otel.SetTracerProvider(tp)
+
+	ctx, span := tp.Tracer("test").Start(context.Background(), "test-root")
+	wantTraceID := span.SpanContext().TraceID().String()
+	defer span.End()
+
+	ag := &mockResultProvider{
+		filesReviewed: 2,
+		inputTokens:   10,
+		outputTokens:  5,
+		totalTokens:   15,
+	}
+	got := captureStdout(t, func() {
+		err := emitRunResult(ctx, ag, nil, time.Now(), "json", "developer", nil)
+		if err != nil {
+			t.Fatalf("unexpected error: %v", err)
+		}
+	})
+	var out jsonOutput
+	if err := json.Unmarshal([]byte(got), &out); err != nil {
+		t.Fatalf("unmarshal: %v", err)
+	}
+	if out.TraceID != wantTraceID {
+		t.Errorf("trace_id = %q, want %q", out.TraceID, wantTraceID)
+	}
+}
+
+func TestEmitRunResult_JSONNoFilesTraceID(t *testing.T) {
+	tp := sdktrace.NewTracerProvider()
+	defer tp.Shutdown(context.Background())
+	otel.SetTracerProvider(tp)
+
+	ctx, span := tp.Tracer("test").Start(context.Background(), "test-root")
+	wantTraceID := span.SpanContext().TraceID().String()
+	defer span.End()
+
+	ag := &mockResultProvider{filesReviewed: 0}
+	got := captureStdout(t, func() {
+		err := emitRunResult(ctx, ag, nil, time.Now(), "json", "developer", nil)
+		if err != nil {
+			t.Fatalf("unexpected error: %v", err)
+		}
+	})
+	var out jsonOutput
+	if err := json.Unmarshal([]byte(got), &out); err != nil {
+		t.Fatalf("unmarshal: %v", err)
+	}
+	if out.Status != "skipped" {
+		t.Errorf("status = %q, want skipped", out.Status)
+	}
+	if out.TraceID != wantTraceID {
+		t.Errorf("trace_id = %q, want %q", out.TraceID, wantTraceID)
+	}
+}

cmd/opencodereview/output.go

@@ -240,6 +240,7 @@ type jsonToolCalls struct {
 
 type jsonOutput struct {
 	Status         string               `json:"status"`
+	TraceID        string               `json:"trace_id,omitempty"`
 	Message        string               `json:"message,omitempty"`
 	Summary        *jsonSummary         `json:"summary,omitempty"`
 	ToolCalls      *jsonToolCalls       `json:"tool_calls"`
@@ -263,9 +264,10 @@ func outputJSON(comments []model.LlmComment) error {
 
 func outputJSONWithWarnings(comments []model.LlmComment, warnings []agent.AgentWarning,
 	filesReviewed, inputTokens, outputTokens, totalTokens, cacheReadTokens, cacheWriteTokens int64,
-	duration time.Duration, projectSummary string, toolCalls map[string]int64) error {
+	duration time.Duration, projectSummary string, toolCalls map[string]int64, traceID string) error {
 	out := jsonOutput{
 		Status:   "success",
+		TraceID:  traceID,
 		Comments: comments,
 		Summary: &jsonSummary{
 			FilesReviewed:    filesReviewed,
@@ -311,9 +313,10 @@ func outputJSONWithWarnings(comments []model.LlmComment, warnings []agent.AgentW
 	return enc.Encode(out)
 }
 
-func outputJSONNoFiles() error {
+func outputJSONNoFiles(traceID string) error {
 	out := jsonOutput{
 		Status:   "skipped",
+		TraceID:  traceID,
 		Message:  "No supported files changed.",
 		Comments: []model.LlmComment{},
 		ToolCalls: &jsonToolCalls{

cmd/opencodereview/output_helpers_test.go

@@ -168,8 +168,7 @@ func TestOutputJSONWithWarnings_NoCommentsSubtaskError(t *testing.T) {
 	os.Stdout = w
 
 	warnings := []agent.AgentWarning{{Type: "subtask_error", File: "x.go", Message: "fail"}}
-	err := outputJSONWithWarnings(nil, warnings, 1, 10, 5, 15, 0, 0, time.Second, "", nil)
-
+	err := outputJSONWithWarnings(nil, warnings, 1, 10, 5, 15, 0, 0, time.Second, "", nil, "abc123trace")
 	w.Close()
 	os.Stdout = old
 
@@ -188,6 +187,9 @@ func TestOutputJSONWithWarnings_NoCommentsSubtaskError(t *testing.T) {
 	if !strings.Contains(out.Message, "errors") {
 		t.Errorf("message = %q, expected to mention errors", out.Message)
 	}
+	if out.TraceID != "abc123trace" {
+		t.Errorf("trace_id = %q, want abc123trace", out.TraceID)
+	}
 }
 
 func TestStatusBadge(t *testing.T) {
@@ -275,8 +277,7 @@ func TestOutputJSONWithWarnings(t *testing.T) {
 
 	comments := []model.LlmComment{{Path: "b.go", Content: "test"}}
 	warnings := []agent.AgentWarning{{Type: "subtask_error", File: "c.go", Message: "failed"}}
-	err := outputJSONWithWarnings(comments, warnings, 5, 100, 50, 150, 10, 5, 3*time.Second, "summary", map[string]int64{"file_read": 3})
-
+	err := outputJSONWithWarnings(comments, warnings, 5, 100, 50, 150, 10, 5, 3*time.Second, "summary", map[string]int64{"file_read": 3}, "trace-xyz-789")
 	w.Close()
 	os.Stdout = old
 
@@ -301,6 +302,9 @@ func TestOutputJSONWithWarnings(t *testing.T) {
 	if out.ToolCalls == nil || out.ToolCalls.Total != 3 {
 		t.Errorf("ToolCalls.Total = %v", out.ToolCalls)
 	}
+	if out.TraceID != "trace-xyz-789" {
+		t.Errorf("trace_id = %q, want trace-xyz-789", out.TraceID)
+	}
 }
 
 func TestOutputJSONWithWarnings_NoCommentsNoErrors(t *testing.T) {
@@ -309,8 +313,7 @@ func TestOutputJSONWithWarnings_NoCommentsNoErrors(t *testing.T) {
 	os.Stdout = w
 
 	warnings := []agent.AgentWarning{{Type: "warning", Message: "something"}}
-	err := outputJSONWithWarnings(nil, warnings, 2, 50, 20, 70, 0, 0, time.Second, "", nil)
-
+	err := outputJSONWithWarnings(nil, warnings, 2, 50, 20, 70, 0, 0, time.Second, "", nil, "")
 	w.Close()
 	os.Stdout = old
 
@@ -336,7 +339,7 @@ func TestOutputJSONNoFiles(t *testing.T) {
 	r, w, _ := os.Pipe()
 	os.Stdout = w
 
-	err := outputJSONNoFiles()
+	err := outputJSONNoFiles("test-trace-id-456")
 
 	w.Close()
 	os.Stdout = old
@@ -353,6 +356,9 @@ func TestOutputJSONNoFiles(t *testing.T) {
 	if out.Status != "skipped" {
 		t.Errorf("status = %q, want skipped", out.Status)
 	}
+	if out.TraceID != "test-trace-id-456" {
+		t.Errorf("trace_id = %q, want test-trace-id-456", out.TraceID)
+	}
 }
 
 func captureStdout(t *testing.T, fn func()) string {

cmd/opencodereview/review_cmd.go

@@ -13,6 +13,8 @@ import (
 	"github.com/open-code-review/open-code-review/internal/mcp"
 	"github.com/open-code-review/open-code-review/internal/telemetry"
 	"github.com/open-code-review/open-code-review/internal/tool"
+
+	"go.opentelemetry.io/otel/codes"
 )
 
 func runReview(args []string) error {
@@ -104,11 +106,23 @@ func runReview(args []string) error {
 
 	ctx, span := telemetry.StartSpan(context.Background(), "review.run")
 	defer span.End()
+	telemetry.SetAttr(span, "review.repo", cc.RepoDir)
+	telemetry.SetAttr(span, "review.from", opts.from)
+	telemetry.SetAttr(span, "review.to", opts.to)
+	telemetry.SetAttr(span, "review.model", rt.Model)
+	var traceID string
+	if telemetry.IsEnabled() {
+		traceID = telemetry.TraceIDFromContext(ctx)
+		if opts.outputFormat != "json" {
+			fmt.Fprintf(os.Stderr, "[ocr] TraceID: %s\n", traceID)
+		}
+	}
 	startTime := time.Now()
 
 	comments, err := ag.Run(ctx)
 	if err != nil {
-		telemetry.SetAttr(span, "error", err.Error())
+		span.SetStatus(codes.Error, err.Error())
+		span.RecordError(err)
 		return fmt.Errorf("review failed: %w", err)
 	}
 

cmd/opencodereview/scan_cmd.go

@@ -3,6 +3,7 @@ package main
 import (
 	"context"
 	"fmt"
+	"os"
 	"strings"
 	"time"
 
@@ -11,6 +12,8 @@ import (
 	"github.com/open-code-review/open-code-review/internal/scan"
 	"github.com/open-code-review/open-code-review/internal/telemetry"
 	"github.com/open-code-review/open-code-review/internal/tool"
+
+	"go.opentelemetry.io/otel/codes"
 )
 
 // scanOptions mirrors reviewOptions for the full-scan subcommand. The two
@@ -207,11 +210,19 @@ func runScan(args []string) error {
 
 	ctx, span := telemetry.StartSpan(context.Background(), "scan.run")
 	defer span.End()
+	var traceID string
+	if telemetry.IsEnabled() {
+		traceID = telemetry.TraceIDFromContext(ctx)
+		if opts.outputFormat != "json" {
+			fmt.Fprintf(os.Stderr, "[ocr] TraceID: %s\n", traceID)
+		}
+	}
 	startTime := time.Now()
 
 	comments, err := ag.Run(ctx)
 	if err != nil {
-		telemetry.SetAttr(span, "error", err.Error())
+		span.SetStatus(codes.Error, err.Error())
+		span.RecordError(err)
 		return fmt.Errorf("scan failed: %w", err)
 	}
 

cmd/opencodereview/shared.go

@@ -276,8 +276,10 @@ func emitRunResult(
 		telemetry.RecordCommentsGenerated(ctx, int64(len(comments)))
 	}
 
+	traceID := telemetry.TraceIDFromContext(ctx)
+
 	if outputFormat == "json" && len(comments) == 0 && ag.FilesReviewed() == 0 {
-		return outputJSONNoFiles()
+		return outputJSONNoFiles(traceID)
 	}
 
 	// Agent-text audiences need stdout back before PrintTraceSummary so the
@@ -296,7 +298,7 @@ func emitRunResult(
 		return outputJSONWithWarnings(comments, ag.Warnings(), ag.FilesReviewed(),
 			ag.TotalInputTokens(), ag.TotalOutputTokens(), ag.TotalTokensUsed(),
 			ag.TotalCacheReadTokens(), ag.TotalCacheWriteTokens(), duration,
-			ag.ProjectSummary(), ag.ToolCalls())
+			ag.ProjectSummary(), ag.ToolCalls(), traceID)
 	}
 	outputTextWithWarnings(comments, ag.Warnings())
 	if summary := ag.ProjectSummary(); summary != "" {