Merge pull request #640 from axw/max-spans-zero

ELASTIC_APM_TRANSACTION_MAX_SPANS=0 disables spans

CHANGELOG.md

@@ -7,6 +7,7 @@
  - module/apmgoredis: add Client.RedisClient (#613)
  - Introduce apm.TraceFormatter, for formatting trace IDs (#635)
  - Report error cause(s), add support for errors.Unwrap (#638)
+ - Setting `ELASTIC_APM_TRANSACTION_MAX_SPANS` to 0 now disables all spans (#640)
 
 ## [v1.5.0](https://github.com/elastic/apm-agent-go/releases/tag/v1.5.0)
 

span.go

@@ -101,7 +101,7 @@ func (tx *Transaction) StartSpanOptions(name, spanType string, opts SpanOptions)
 	defer tx.TransactionData.mu.Unlock()
 	if !span.traceContext.Options.Recorded() {
 		span.tracer = nil // span is dropped
-	} else if tx.maxSpans > 0 && tx.spansCreated >= tx.maxSpans {
+	} else if tx.maxSpans >= 0 && tx.spansCreated >= tx.maxSpans {
 		span.tracer = nil // span is dropped
 		tx.spansDropped++
 	} else {

tracer.go

@@ -581,8 +581,10 @@ func (t *Tracer) SetSampler(s Sampler) {
 }
 
 // SetMaxSpans sets the maximum number of spans that will be added
-// to a transaction before dropping spans. If set to a non-positive
-// value, the number of spans is unlimited.
+// to a transaction before dropping spans.
+//
+// Passing in zero will disable all spans, while negative values will
+// permit an unlimited number of spans.
 func (t *Tracer) SetMaxSpans(n int) {
 	t.maxSpansMu.Lock()
 	t.maxSpans = n

tracer_test.go

@@ -83,29 +83,34 @@ func TestTracerFlushEmpty(t *testing.T) {
 }
 
 func TestTracerMaxSpans(t *testing.T) {
-	tracer, r := transporttest.NewRecorderTracer()
-	defer tracer.Close()
-
-	tracer.SetMaxSpans(2)
-	tx := tracer.StartTransaction("name", "type")
-	// SetMaxSpans only affects transactions started
-	// after the call.
-	tracer.SetMaxSpans(99)
-
-	s0 := tx.StartSpan("name", "type", nil)
-	s1 := tx.StartSpan("name", "type", nil)
-	s2 := tx.StartSpan("name", "type", nil)
-	tx.End()
-
-	assert.False(t, s0.Dropped())
-	assert.False(t, s1.Dropped())
-	assert.True(t, s2.Dropped())
-	s0.End()
-	s1.End()
-	s2.End()
+	test := func(n int) {
+		t.Run(fmt.Sprint(n), func(t *testing.T) {
+			tracer, r := transporttest.NewRecorderTracer()
+			defer tracer.Close()
+
+			tracer.SetMaxSpans(n)
+			tx := tracer.StartTransaction("name", "type")
+			defer tx.End()
+
+			// SetMaxSpans only affects transactions started
+			// after the call.
+			tracer.SetMaxSpans(99)
+
+			for i := 0; i < n; i++ {
+				span := tx.StartSpan("name", "type", nil)
+				assert.False(t, span.Dropped())
+				span.End()
+			}
+			span := tx.StartSpan("name", "type", nil)
+			assert.True(t, span.Dropped())
+			span.End()
 
-	tracer.Flush(nil)
-	assert.Len(t, r.Payloads().Spans, 2)
+			tracer.Flush(nil)
+			assert.Len(t, r.Payloads().Spans, n)
+		})
+	}
+	test(0)
+	test(23)
 }
 
 func TestTracerErrors(t *testing.T) {