feat: option for propagationHeaders which are used in fetch patch

packages/otel/src/bootstrap/main.ts

@@ -1,6 +1,7 @@
-import { type SpanProcessor } from '@opentelemetry/sdk-trace-node'
+import { BatchSpanProcessor, ConsoleSpanExporter, type SpanProcessor } from '@opentelemetry/sdk-trace-node'
 import type { Instrumentation } from '@opentelemetry/instrumentation'
-import { GET_TRACER, SHUTDOWN_TRACERS } from '../constants.js'
+import { GET_TRACE_CONTEXT_FORWARDER, GET_TRACER, SHUTDOWN_TRACERS } from '../constants.js'
+import { Context, context, W3CTraceContextPropagator } from '../opentelemetry.ts'
 
 export interface TracerProviderOptions {
   serviceName: string
@@ -11,6 +12,7 @@
   siteName: string
   instrumentations?: (Instrumentation | Promise<Instrumentation>)[]
   spanProcessors?: (SpanProcessor | Promise<SpanProcessor>)[]
+  propagationHeaders?: Headers
 }
 
 export const createTracerProvider = async (options: TracerProviderOptions) => {
@@ -43,16 +45,38 @@
   })
 
   nodeTracerProvider.register({
-    propagator: new W3CTraceContextPropagator(),
+    propagator: new W3CTraceContextPropagator()
+
   })
 
+  let traceContextForwarder: (propagator: W3CTraceContextPropagator, requestHeaders: Headers) => void
+
+  if (options.propagationHeaders) {
+    traceContextForwarder = (propagator: W3CTraceContextPropagator, requestHeaders: Headers): Context => {
+      const getter = {
+        keys: (carrier: Headers) => [...carrier.keys()],
+        get: (carrier: Headers, key: string) => carrier.get(key) || undefined,
+      }
+      const extractedContext = propagator.extract(context.active(), options.propagationHeaders, getter)
+
+      propagator?.inject(context.active(), requestHeaders, {
+        set: (carrier, key, value) => {
+          carrier.set(key, value)
+        },
+      })
+
+      return extractedContext
+    }
+  }
+
   const instrumentations = await Promise.all(options.instrumentations ?? [])
 
   registerInstrumentations({
     instrumentations,
     tracerProvider: nodeTracerProvider,
   })
 
+
   const { trace } = await import('@opentelemetry/api')
   const { SugaredTracer } = await import('@opentelemetry/api/experimental')
   const { default: pkg } = await import('../../package.json', { with: { type: 'json' } })
@@ -70,6 +94,15 @@
     },
   })
 
+  Object.defineProperty(globalThis, GET_TRACE_CONTEXT_FORWARDER, {
+    enumerable: false,
+    configurable: true,
+    writable: false,
+    value: function() {
+      return traceContextForwarder
+    },
+  })
+
   Object.defineProperty(globalThis, SHUTDOWN_TRACERS, {
     enumerable: false,
     configurable: true,

packages/otel/src/constants.ts

@@ -1,3 +1,4 @@
 export const GET_TRACER = '__netlify__getTracer'
 export const SHUTDOWN_TRACERS = '__netlify__shutdownTracers'
+export const GET_TRACE_CONTEXT_FORWARDER = '__netlify__getTraceContextForwarder'
 export const TRACE_PREFIX = '__nfOTLPTrace'

packages/otel/src/instrumentations/fetch.ts

@@ -1,7 +1,8 @@
 import * as api from '@opentelemetry/api'
 import { SugaredTracer } from '@opentelemetry/api/experimental'
-import { _globalThis } from '@opentelemetry/core'
+import { _globalThis, W3CTraceContextPropagator } from '@opentelemetry/core'
 import { InstrumentationConfig, type Instrumentation } from '@opentelemetry/instrumentation'
+import { getTraceContextForwarder } from '../main.ts'
 
 export interface FetchInstrumentationConfig extends InstrumentationConfig {
   getRequestAttributes?(headers: Request): api.Attributes
@@ -26,9 +27,9 @@ export class FetchInstrumentation implements Instrumentation {
     return this.config
   }
 
-  setConfig(): void {}
+  setConfig(): void { }
 
-  setMeterProvider(): void {}
+  setMeterProvider(): void { }
   setTracerProvider(provider: api.TracerProvider): void {
     this.provider = provider
   }
@@ -120,6 +121,23 @@ export class FetchInstrumentation implements Instrumentation {
         return await originalFetch(resource, options)
       }
 
+      const traceContextForwarder = getTraceContextForwarder()
+      if (options?.headers && traceContextForwarder) {
+        const headers = new Headers(options.headers)
+        const extractedContext = traceContextForwarder(new W3CTraceContextPropagator(), headers)
+
+        // Replace headers in options with the mutated version
+        const nextOptions: RequestInit = { ...options, headers }
+
+        return tracer.startActiveSpan('fetch', {}, extractedContext, async (span) => {
+          const request = new Request(resource, nextOptions)
+          this.annotateFromRequest(span, request)
+          const response = await originalFetch(request, nextOptions)
+          this.annotateFromResponse(span, response)
+          return response
+        })
+      }
+
       return tracer.withActiveSpan('fetch', async (span) => {
         const request = new Request(resource, options)
         this.annotateFromRequest(span, request)

packages/otel/src/main.ts

@@ -1,16 +1,22 @@
 import { type SugaredSpanOptions, type SugaredTracer } from '@opentelemetry/api/experimental'
-import { GET_TRACER, SHUTDOWN_TRACERS } from './constants.js'
+import { GET_TRACER, SHUTDOWN_TRACERS, GET_TRACE_CONTEXT_FORWARDER } from './constants.js'
 import type { Context, Span } from '@opentelemetry/api'
+import { W3CTraceContextPropagator } from '@opentelemetry/core'
 
 type GlobalThisExtended = typeof globalThis & {
   [GET_TRACER]?: (name?: string, version?: string) => SugaredTracer | undefined
   [SHUTDOWN_TRACERS]?: () => void
+  [GET_TRACE_CONTEXT_FORWARDER]?: () => ((propagator: W3CTraceContextPropagator, requestHeaders: Headers) => Context) | undefined
 }
 
 export const getTracer = (name?: string, version?: string): SugaredTracer | undefined => {
   return (globalThis as GlobalThisExtended)[GET_TRACER]?.(name, version)
 }
 
+export const getTraceContextForwarder = (): ((propagator: W3CTraceContextPropagator, requestHeaders: Headers) => Context) | undefined => {
+  return (globalThis as GlobalThisExtended)[GET_TRACE_CONTEXT_FORWARDER]?.()
+}
+
 export const shutdownTracers = async (): Promise<void> => {
   return (globalThis as GlobalThisExtended)[SHUTDOWN_TRACERS]?.()
 }