chore: Added supportability metrics Supportability/Nodejs/SpanEvent/<Links|Events>/Dropped when limit of 100 is exceeded (newrelic#3688)

bizob2828 · web-flow · commit a247d31fc9c2 · 2026-01-26T12:38:33.000-05:00
diff --git a/lib/metrics/names.js b/lib/metrics/names.js
@@ -325,7 +325,9 @@ const SPAN_EVENTS = {
   SEEN: SUPPORTABILITY.PREFIX + SPAN_EVENT_PREFIX + 'TotalEventsSeen',
   SENT: SUPPORTABILITY.PREFIX + SPAN_EVENT_PREFIX + 'TotalEventsSent',
   DROPPED: SUPPORTABILITY.PREFIX + SPAN_EVENT_PREFIX + 'Discarded',
-  LIMIT: SUPPORTABILITY.PREFIX + SPAN_EVENT_PREFIX + 'Limit'
+  LIMIT: SUPPORTABILITY.PREFIX + SPAN_EVENT_PREFIX + 'Limit',
+  LINKS_DROPPED: SUPPORTABILITY.NODEJS + '/' + SPAN_EVENT_PREFIX + 'Links/Dropped',
+  EVENTS_DROPPED: SUPPORTABILITY.NODEJS + '/' + SPAN_EVENT_PREFIX + 'Events/Dropped'
 }
 
 const INFINITE_TRACING = {
diff --git a/lib/otel/traces/span-processor.js b/lib/otel/traces/span-processor.js
@@ -23,6 +23,7 @@ const {
   transformTemplate
 } = require('./utils.js')
 const defaultLogger = require('#agentlib/logger.js').child({ component: 'span-processor' })
+const { SPAN_EVENTS } = require('#agentlib/metrics/names.js')
 
 const {
   SPAN_STATUS_CODE
@@ -155,7 +156,10 @@ module.exports = class NrSpanProcessor {
         event: span.events[i],
         spanContext
       })
-      segment.addTimedEvent(event)
+      const added = segment.addTimedEvent(event)
+      if (!added) {
+        this.agent.metrics.getOrCreateMetric(SPAN_EVENTS.EVENTS_DROPPED).incrementCallCount()
+      }
     }
   }
 
@@ -181,7 +185,10 @@ module.exports = class NrSpanProcessor {
         spanContext,
         timestamp
       })
-      segment.addSpanLink(link)
+      const added = segment.addSpanLink(link)
+      if (!added) {
+        this.agent.metrics.getOrCreateMetric(SPAN_EVENTS.LINKS_DROPPED).incrementCallCount()
+      }
     }
   }
 
diff --git a/lib/transaction/trace/segment.js b/lib/transaction/trace/segment.js
@@ -296,20 +296,34 @@ TraceSegment.prototype.captureExternalAttributes = function captureExternalAttri
   this.addAttribute('procedure', method)
 }
 
+/**
+ * Adds SpanLink event to TraceSegment unless the size limit has been reached
+ *
+ * @param {SpanLink} spanLink to add to TraceSegment
+ * @returns {boolean} if span link was added or not
+ */
 TraceSegment.prototype.addSpanLink = function addSpanLink(spanLink) {
   if (this.spanLinks.length === 100) {
     this.logger.trace({ spanLink }, 'Span links limit reached. Not adding new link.')
-    return
+    return false
   }
   this.spanLinks.push(spanLink)
+  return true
 }
 
+/**
+ * Adds TimedEvent event to TraceSegment unless the size limit has been reached
+ *
+ * @param {TimedEvent} timedEvent to add to TraceSegment
+ * @returns {boolean} if timed event was added or not
+ */
 TraceSegment.prototype.addTimedEvent = function addTimedEvent(timedEvent) {
   if (this.timedEvents.length === 100) {
     this.logger.trace({ timedEvent }, 'Timed event limit reached. Not adding new event.')
-    return
+    return false
   }
   this.timedEvents.push(timedEvent)
+  return true
 }
 
 module.exports = TraceSegment
diff --git a/test/unit/lib/otel/traces/span-procesor.test.js b/test/unit/lib/otel/traces/span-procesor.test.js
@@ -271,7 +271,7 @@ test('reconcileEvents skips work if no events', (t) => {
 })
 
 test('reconcileEvents adds remapped events to the segment', (t) => {
-  t.plan(2)
+  t.plan(3)
   const { agent, processor, tracer } = t.nr
 
   helper.runInTransaction(agent, (tx) => {
@@ -296,7 +296,32 @@ test('reconcileEvents adds remapped events to the segment', (t) => {
       return spanContext.call(span)
     }
     processor.reconcileEvents({ segment, span })
+    t.assert.ok(!agent.metrics._metrics.unscoped['Supportability/Nodejs/SpanEvent/Events/Dropped'])
+
+    tx.end()
+  })
+})
+
+test('reconcileEvents logs `Supportability/Nodejs/SpanEvent/Links/Dropped` when events exceed 100', (t) => {
+  t.plan(2)
+  const { agent, processor, tracer } = t.nr
 
+  helper.runInTransaction(agent, (tx) => {
+    const span = createHttpClientSpan({ tracer })
+    processor.onStart(span)
+
+    for (let i = 0; i < 105; i++) {
+      span.events.push({
+        name: `test-event-${i}`,
+        attributes: { test: 'attr' },
+        time: [1, 0]
+      })
+    }
+
+    const { segment } = span[otelSynthesis]
+    processor.reconcileEvents({ segment, span })
+    t.assert.equal(agent.metrics._metrics.unscoped['Supportability/Nodejs/SpanEvent/Events/Dropped'].callCount, 5)
+    t.assert.equal(segment.timedEvents.length, 100)
     tx.end()
   })
 })
@@ -320,7 +345,7 @@ test('reconcileLinks skips work if no links', (t) => {
 })
 
 test('reconcileLinks adds remapped links to the segment', (t) => {
-  t.plan(2)
+  t.plan(3)
   const { agent, processor, tracer } = t.nr
 
   helper.runInTransaction(agent, (tx) => {
@@ -347,7 +372,34 @@ test('reconcileLinks adds remapped links to the segment', (t) => {
       return spanContext.call(span)
     }
     processor.reconcileLinks({ segment, otelSpan: span })
+    t.assert.ok(!agent.metrics._metrics.unscoped['Supportability/Nodejs/SpanEvent/Links/Dropped'])
+
+    tx.end()
+  })
+})
 
+test('reconcileLinks logs `Supportability/Nodejs/SpanEvent/Links/Dropped` when links exceed 100', (t) => {
+  t.plan(2)
+  const { agent, processor, tracer } = t.nr
+
+  helper.runInTransaction(agent, (tx) => {
+    const span = createHttpClientSpan({ tracer })
+    processor.onStart(span)
+
+    for (let i = 0; i < 105; i++) {
+      span.links.push({
+        attributes: { test: `attr-${i}` },
+        context: {
+          spanId: 'linked-span',
+          traceId: 'linked-trace'
+        }
+      })
+    }
+
+    const { segment } = span[otelSynthesis]
+    processor.reconcileLinks({ segment, otelSpan: span })
+    t.assert.equal(agent.metrics._metrics.unscoped['Supportability/Nodejs/SpanEvent/Links/Dropped'].callCount, 5)
+    t.assert.equal(segment.spanLinks.length, 100)
     tx.end()
   })
 })
diff --git a/test/unit/transaction/trace/segment.test.js b/test/unit/transaction/trace/segment.test.js
@@ -705,7 +705,8 @@ test('addSpanLink', async (t) => {
   await test('adds link to the internal array', (t) => {
     const { segment } = t.nr
     assert.equal(segment.spanLinks.length, 0)
-    segment.addSpanLink({ fake: 'link' })
+    const added = segment.addSpanLink({ fake: 'link' })
+    assert.equal(added, true)
     assert.equal(segment.spanLinks.length, 1)
     assert.deepStrictEqual(segment.spanLinks[0], { fake: 'link' })
   })
@@ -718,7 +719,8 @@ test('addSpanLink', async (t) => {
     }
     assert.equal(segment.spanLinks.length, 100)
 
-    segment.addSpanLink({ to: 'drop' })
+    const added = segment.addSpanLink({ to: 'drop' })
+    assert.equal(added, false)
     assert.equal(segment.spanLinks.length, 100)
     for (const link of segment.spanLinks) {
       assert.deepStrictEqual(link, { fake: 'link' })
@@ -770,7 +772,8 @@ test('addTimedEvent', async (t) => {
   await test('adds event to the internal array', (t) => {
     const { segment } = t.nr
     assert.equal(segment.timedEvents.length, 0)
-    segment.addTimedEvent({ fake: 'event' })
+    const added = segment.addTimedEvent({ fake: 'event' })
+    assert.equal(added, true)
     assert.equal(segment.timedEvents.length, 1)
     assert.deepStrictEqual(segment.timedEvents[0], { fake: 'event' })
   })
@@ -783,7 +786,8 @@ test('addTimedEvent', async (t) => {
     }
     assert.equal(segment.timedEvents.length, 100)
 
-    segment.addTimedEvent({ to: 'drop' })
+    const added = segment.addTimedEvent({ to: 'drop' })
+    assert.equal(added, false)
     assert.equal(segment.timedEvents.length, 100)
     for (const event of segment.timedEvents) {
       assert.deepStrictEqual(event, { fake: 'event' })
