fix(prisma): use real trace context in getTraceParent for DBM correlation.

packages/datadog-instrumentations/src/prisma.js

@@ -4,6 +4,7 @@ const {
   channel,
   addHook
 } = require('./helpers/instrument')
+const { storage } = require('../../datadog-core')
 
 const prismaEngineStart = channel('apm:prisma:engine:start')
 const tracingChannel = require('dc-polyfill').tracingChannel
@@ -23,7 +24,29 @@ class TracingHelper {
 
   // needs a sampled tracecontext to generate engine spans
   getTraceParent (context) {
-    return '00-aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa-bbbbbbbbbbbbbbbb-01' // valid sampled traceparent
+    // try to get span from current async storage context
+    const store = storage('legacy').getStore()
+    const span = store && store.span
+
+    if (span && typeof span.context === 'function') {
+      const spanContext = span.context()
+      if (spanContext && typeof spanContext.toTraceparent === 'function') {
+        let traceparent = spanContext.toTraceparent()
+
+        // force the sampled flag to '01' for Prisma's engine span generation
+        // prisma only generates engine spans when the traceparent indicates the trace is sampled
+        // this ensures engine spans are created and dispatched to dd-trace, which will then
+        // apply its own sampling decision when recording/sending spans
+        // the trace IDs and span IDs remain correct for DBM correlation
+        traceparent = traceparent.replace(/-0[01]$/, '-01')
+
+        return traceparent
+      }
+    }
+
+    // fallback to a valid sampled traceparent if no active span.
+    // this ensures Prisma can generate engine spans even when there's no active dd-trace context
+    return '00-aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa-bbbbbbbbbbbbbbbb-01'
   }
 
   dispatchEngineSpans (spans) {

packages/datadog-plugin-prisma/test/index.spec.js

@@ -204,6 +204,51 @@ describe('Plugin', () => {
             tracingPromise
           ])
         })
+
+        it('should return real traceparent from active span context', async () => {
+          let capturedTraceparent
+          const tracingPromise = agent.assertSomeTraces(traces => {
+            // Get the trace ID and span ID from the created span
+            const clientSpan = traces[0].find(span => span.meta['prisma.type'] === 'client')
+            assert.ok(clientSpan != null)
+
+            // Verify the traceparent is not the hardcoded fallback
+            assert.notEqual(capturedTraceparent, '00-aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa-bbbbbbbbbbbbbbbb-01')
+
+            // Verify it matches W3C traceparent format
+            const traceparentRegex = /^00-[a-f0-9]{32}-[a-f0-9]{16}-[0-9]{2}$/
+            assert.ok(traceparentRegex.test(capturedTraceparent),
+              `Invalid traceparent format: ${capturedTraceparent}`)
+
+            // Extract trace ID from traceparent (format: version-traceid-spanid-flags)
+            const [, traceparentTraceId] = capturedTraceparent.split('-')
+
+            // Convert the span's trace_id to hex for comparison
+            const spanTraceIdHex = clientSpan.trace_id.toString(16).padStart(32, '0')
+
+            // The last 16 characters of the traceparent trace ID should match
+            // the span's trace ID (dd-trace uses 64-bit trace IDs by default)
+            assert.ok(traceparentTraceId.endsWith(spanTraceIdHex.slice(-16)),
+              `Traceparent trace ID ${traceparentTraceId} should contain span trace ID ${spanTraceIdHex}`)
+          })
+
+          // Capture the traceparent during the query
+          await prismaClient.$queryRaw`SELECT 1`.then(() => {
+            // Get traceparent while span is still active
+            capturedTraceparent = tracingHelper.getTraceParent()
+          })
+
+          await tracingPromise
+        })
+
+        it('should return fallback traceparent when no active span', () => {
+          // Get traceparent outside of a traced operation
+          // This should return the fallback value since there's no active span
+          const result = tracingHelper.getTraceParent()
+
+          // Should be the valid sampled fallback traceparent
+          assert.strictEqual(result, '00-aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa-bbbbbbbbbbbbbbbb-01')
+        })
       })
 
       describe('with configuration', () => {