Remove ErrorBusy metric since it duplicates SpansDropped (#1091)

Signed-off-by: Callum Styan <callumstyan@gmail.com>

cmd/collector/app/metrics.go

@@ -40,8 +40,6 @@ type SpanProcessorMetrics struct {
 	BatchSize metrics.Gauge // size of span batch
 	// QueueLength measures the size of the internal span queue
 	QueueLength metrics.Gauge
-	// ErrorBusy counts number of return ErrServerBusy
-	ErrorBusy metrics.Counter
 	// SavedOkBySvc contains span and trace counts by service
 	SavedOkBySvc  metricsBySvc  // spans actually saved
 	SavedErrBySvc metricsBySvc  // spans failed to save
@@ -87,7 +85,6 @@ func NewSpanProcessorMetrics(serviceMetrics metrics.Factory, hostMetrics metrics
 		SpansDropped:   hostMetrics.Counter(metrics.Options{Name: "spans.dropped", Tags: nil}),
 		BatchSize:      hostMetrics.Gauge(metrics.Options{Name: "batch-size", Tags: nil}),
 		QueueLength:    hostMetrics.Gauge(metrics.Options{Name: "queue-length", Tags: nil}),
-		ErrorBusy:      hostMetrics.Counter(metrics.Options{Name: "error.busy", Tags: nil}),
 		SavedOkBySvc:   newMetricsBySvc(serviceMetrics.Namespace(metrics.NSOptions{Name: "", Tags: map[string]string{"result": "ok"}}), "saved-by-svc"),
 		SavedErrBySvc:  newMetricsBySvc(serviceMetrics.Namespace(metrics.NSOptions{Name: "", Tags: map[string]string{"result": "err"}}), "saved-by-svc"),
 		spanCounts:     spanCounts,

cmd/collector/app/span_processor.go

@@ -140,9 +140,5 @@ func (sp *spanProcessor) enqueueSpan(span *model.Span, originalFormat string) bo
 		queuedTime: time.Now(),
 		span:       span,
 	}
-	addedToQueue := sp.queue.Produce(item)
-	if !addedToQueue {
-		sp.metrics.ErrorBusy.Inc(1)
-	}
-	return addedToQueue
+	return sp.queue.Produce(item)
 }

cmd/collector/app/span_processor_test.go

@@ -136,8 +136,6 @@ func TestBySvcMetrics(t *testing.T) {
 			// we defined the queue capacity as 0, all submitted items are dropped.
 			// The debug spans are always accepted.
 			expected = append(expected, metricstest.ExpectedMetric{
-				Name: "host.error.busy", Value: 2,
-			}, metricstest.ExpectedMetric{
 				Name: "host.spans.dropped", Value: 2,
 			})
 		} else {