gracefully handle failing traces

Closes #1

Author: enisdenjo

__snapshots__/tracer_test.snap

@@ -527,3 +527,11 @@
  "size": 1
 }
 ---
+
+[TestSendReportError - 1]
+[]string{"failed to send report for operation \"id\": test fail send report"}
+---
+
+[TestSendReportServerError - 1]
+[]string{"failed to send report for operation \"a0\": report sending failed with 400 Bad Request: test server error", "failed to send report for operation \"a1\": report sending failed with 500 Internal Server Error (no body)"}
+---

logger.go

@@ -0,0 +1,13 @@
+package gqlhive
+
+import "log"
+
+type Logger interface {
+	Printf(format string, v ...any)
+}
+
+// NewLogger creates a new Logger instance that writes to the standard log output
+// with the prefix "[gqlhive] " and includes the standard logging attribute such as timestamp.
+func NewLogger() Logger {
+	return log.New(log.Writer(), "[gqlhive] ", log.LstdFlags|log.Lmsgprefix)
+}

tracer.go

@@ -23,6 +23,7 @@ type Tracer struct {
 	generateID        GenerateID
 	sendReportTimeout time.Duration
 	sendReport        SendReport
+	log               Logger
 }
 
 var _ interface {
@@ -44,6 +45,7 @@ func NewTracer(target, token string, opts ...TracerOption) *Tracer {
 		generateID:        defaultGenerateID,
 		sendReportTimeout: defaultSendReportTimeout,
 		sendReport:        defaultSendReport,
+		log:               defaultLogger,
 	}
 	for _, opt := range opts {
 		opt.set(tracer)
@@ -124,8 +126,8 @@ func (tracer Tracer) InterceptResponse(ctx context.Context, next graphql.Respons
 
 		err := queueOperation(operation)
 		if err != nil {
-			// TODO: report gracefully
-			panic(err)
+			tracer.log.Printf("failed to queue operation %q: %v", operation.ID, err)
+			return
 		}
 
 		// TODO: implement send retry
@@ -148,8 +150,7 @@ func (tracer Tracer) InterceptResponse(ctx context.Context, next graphql.Respons
 		if tracer.sendReportTimeout == 0 {
 			err := doSend(ctx)
 			if err != nil {
-				// TODO: report gracefully
-				panic(err)
+				tracer.log.Printf("failed to send report for operation %q: %v", operation.ID, err)
 			}
 			return
 		}
@@ -165,8 +166,7 @@ func (tracer Tracer) InterceptResponse(ctx context.Context, next graphql.Respons
 					context.TODO(),
 				)
 				if err != nil {
-					// TODO: report gracefully
-					panic(err)
+					tracer.log.Printf("failed to send queued report for operation %q: %v", operation.ID, err)
 				}
 			}()
 		}

tracer_test.go

@@ -298,3 +298,80 @@ func TestSendingReportsOverHTTP(t *testing.T) {
 	res := map[string]any{}
 	client.New(srv).MustPost("{ todos { id } }", &res)
 }
+
+//
+
+type testLogger struct {
+	logs []string
+}
+
+func newTestLogger() *testLogger {
+	return &testLogger{}
+}
+
+func (l *testLogger) Printf(format string, v ...any) {
+	l.logs = append(l.logs, fmt.Sprintf(format, v...))
+}
+
+func TestSendReportError(t *testing.T) {
+	srv := handler.New(graph.NewExecutableSchema(graph.Config{Resolvers: &graph.Resolver{}}))
+	srv.AddTransport(transport.POST{})
+
+	testLogger := newTestLogger()
+
+	srv.Use(NewTracer(
+		uu.IDv4().String(),
+		"<token>",
+		WithGenerateID(func(operation string, operationName nullable.TrimmedString) string {
+			return "id"
+		}),
+		WithSendReportTimeout(0),
+		WithSendReport(func(ctx context.Context, endpoint, target, token string, report *Report) error {
+			return fmt.Errorf("test fail send report")
+		}),
+		WithLogger(testLogger),
+	))
+
+	res := map[string]any{}
+	client.New(srv).MustPost("{ todos { id } }", &res)
+
+	snaps.MatchSnapshot(t, testLogger.logs)
+}
+
+func TestSendReportServerError(t *testing.T) {
+	var attempt = 0
+	tserver := httptest.NewServer(http.HandlerFunc(func(res http.ResponseWriter, req *http.Request) {
+		if attempt == 0 {
+			// with body
+			res.WriteHeader(http.StatusBadRequest)
+			res.Write([]byte("test server error"))
+			attempt++
+		} else {
+			// without body
+			res.WriteHeader(http.StatusInternalServerError)
+		}
+	}))
+	defer tserver.Close()
+
+	srv := handler.New(graph.NewExecutableSchema(graph.Config{Resolvers: &graph.Resolver{}}))
+	srv.AddTransport(transport.POST{})
+
+	testLogger := newTestLogger()
+
+	srv.Use(NewTracer(
+		uu.IDv4().String(),
+		"<token>",
+		WithEndpoint(tserver.URL),
+		WithGenerateID(func(operation string, operationName nullable.TrimmedString) string {
+			return fmt.Sprintf("a%d", attempt)
+		}),
+		WithSendReportTimeout(0),
+		WithLogger(testLogger),
+	))
+
+	res := map[string]any{}
+	client.New(srv).MustPost("query a1 { todos { id } }", &res)
+	client.New(srv).MustPost("query a2 { todos { id } }", &res)
+
+	snaps.MatchSnapshot(t, testLogger.logs)
+}

traceroptions.go

@@ -5,6 +5,7 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
+	"io"
 	"net/http"
 	"time"
 
@@ -68,7 +69,14 @@ func defaultSendReport(ctx context.Context, endpoint, target, token string, repo
 	}
 
 	if res.StatusCode != http.StatusOK {
-		return fmt.Errorf("report sending failed with %d %s", res.StatusCode, res.Status)
+		defer res.Body.Close()
+		body, _ := io.ReadAll(res.Body)
+		bodyStr := string(body)
+		if bodyStr == "" {
+			return fmt.Errorf("report sending failed with %s (no body)", res.Status)
+		} else {
+			return fmt.Errorf("report sending failed with %s: %s", res.Status, bodyStr)
+		}
 	}
 
 	return nil
@@ -84,6 +92,17 @@ func WithSendReport(fn SendReport) TracerOption {
 	})
 }
 
+// WithLogger sets the logger to be used by the tracer.
+// The logger is used for reporting errors during tracing. If set to nil, logging is disabled.
+// You can use the standard Go logger or provide a custom implementation (e.g., logrus, zap).
+func WithLogger(logger Logger) TracerOption {
+	return tracerOptionFn(func(tracer *Tracer) {
+		tracer.log = logger
+	})
+}
+
+var defaultLogger = NewLogger()
+
 type TracerOption interface {
 	set(*Tracer)
 }