feat: Make maximum amount of spans configurable (#460)

Co-authored-by: Michi Hoffmann <cleptric@users.noreply.github.com>

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 - fix: Scope values should not override Event values (#446)
 - feat: Extend User inteface by adding Data, Name and Segment (#483)
+- feat: Make maximum amount of spans configurable (#460)
 
 ## 0.14.0
 

client.go

@@ -28,6 +28,11 @@ import (
 // stack trace is often the most useful information.
 const maxErrorDepth = 10
 
+// defaultMaxSpans limits the default number of recorded spans per transaction. The limit is
+// meant to bound memory usage and prevent too large transaction events that
+// would be rejected by Sentry.
+const defaultMaxSpans = 1000
+
 // hostname is the host name reported by the kernel. It is precomputed once to
 // avoid syscalls when capturing events.
 //
@@ -175,6 +180,11 @@ type ClientOptions struct {
 	// Maximum number of breadcrumbs
 	// when MaxBreadcrumbs is negative then ignore breadcrumbs.
 	MaxBreadcrumbs int
+	// Maximum number of spans.
+	//
+	// See https://develop.sentry.dev/sdk/envelopes/#size-limits for size limits
+	// applied during event ingestion. Events that exceed these limits might get dropped.
+	MaxSpans int
 	// An optional pointer to http.Client that will be used with a default
 	// HTTPTransport. Using your own client will make HTTPTransport, HTTPProxy,
 	// HTTPSProxy and CaCerts options ignored.
@@ -250,6 +260,10 @@ func NewClient(options ClientOptions) (*Client, error) {
 		options.MaxErrorDepth = maxErrorDepth
 	}
 
+	if options.MaxSpans == 0 {
+		options.MaxSpans = defaultMaxSpans
+	}
+
 	// SENTRYGODEBUG is a comma-separated list of key=value pairs (similar
 	// to GODEBUG). It is not a supported feature: recognized debug options
 	// may change any time.

client_test.go

@@ -520,3 +520,17 @@ func TestRecover(t *testing.T) {
 		})
 	}
 }
+
+func TestCustomMaxSpansProperty(t *testing.T) {
+	client, _, _ := setupClientTest()
+	assertEqual(t, client.Options().MaxSpans, defaultMaxSpans)
+
+	client.options.MaxSpans = 2000
+	assertEqual(t, client.Options().MaxSpans, 2000)
+
+	properClient, _ := NewClient(ClientOptions{
+		MaxSpans: 3000,
+	})
+
+	assertEqual(t, properClient.Options().MaxSpans, 3000)
+}

span_recorder.go

@@ -4,11 +4,6 @@ import (
 	"sync"
 )
 
-// maxSpans limits the number of recorded spans per transaction. The limit is
-// meant to bound memory usage and prevent too large transaction events that
-// would be rejected by Sentry.
-const maxSpans = 1000
-
 // A spanRecorder stores a span tree that makes up a transaction. Safe for
 // concurrent use. It is okay to add child spans from multiple goroutines.
 type spanRecorder struct {
@@ -20,6 +15,10 @@ type spanRecorder struct {
 // record stores a span. The first stored span is assumed to be the root of a
 // span tree.
 func (r *spanRecorder) record(s *Span) {
+	maxSpans := defaultMaxSpans
+	if client := CurrentHub().Client(); client != nil {
+		maxSpans = client.Options().MaxSpans
+	}
 	r.mu.Lock()
 	defer r.mu.Unlock()
 	if len(r.spans) >= maxSpans {

span_recorder_test.go

@@ -0,0 +1,63 @@
+package sentry
+
+import (
+	"bytes"
+	"context"
+	"fmt"
+	"io"
+	"testing"
+)
+
+func Test_spanRecorder_record(t *testing.T) {
+	testRootSpan := StartSpan(context.Background(), "test", TransactionName("test transaction"))
+
+	for _, tt := range []struct {
+		name           string
+		maxSpans       int
+		toRecordSpans  int
+		expectOverflow bool
+	}{
+		{
+			name:           "record span without problems",
+			maxSpans:       defaultMaxSpans,
+			toRecordSpans:  1,
+			expectOverflow: false,
+		},
+		{
+			name:           "record span with overflow",
+			maxSpans:       2,
+			toRecordSpans:  4,
+			expectOverflow: true,
+		},
+	} {
+		t.Run(tt.name, func(t *testing.T) {
+			logBuffer := bytes.Buffer{}
+			Logger.SetOutput(&logBuffer)
+			defer Logger.SetOutput(io.Discard)
+			spanRecorder := spanRecorder{}
+
+			currentHub.BindClient(&Client{
+				options: ClientOptions{
+					MaxSpans: tt.maxSpans,
+				},
+			})
+			// Unbind the client afterwards, to not affect other tests
+			defer currentHub.stackTop().SetClient(nil)
+
+			for i := 0; i < tt.toRecordSpans; i++ {
+				child := testRootSpan.StartChild(fmt.Sprintf("test %d", i))
+				spanRecorder.record(child)
+			}
+
+			if tt.expectOverflow {
+				assertNotEqual(t, len(spanRecorder.spans), tt.toRecordSpans, "expected overflow")
+			} else {
+				assertEqual(t, len(spanRecorder.spans), tt.toRecordSpans, "expected no overflow")
+			}
+			// check if Logger was called for overflow messages
+			if bytes.Contains(logBuffer.Bytes(), []byte("Too many spans")) && !tt.expectOverflow {
+				t.Error("unexpected overflow log")
+			}
+		})
+	}
+}