lazy load fetch instrumentation only when needed (#5317)

rochdev · web-flow · commit c9b9d086f38a · 2025-02-26T09:33:14.000-05:00
diff --git a/packages/datadog-instrumentations/src/fetch.js b/packages/datadog-instrumentations/src/fetch.js
@@ -1,14 +1,33 @@
 'use strict'
 
-const shimmer = require('../../datadog-shimmer')
-const { channel, tracingChannel } = require('dc-polyfill')
-const { createWrapFetch } = require('./helpers/fetch')
+const { isInServerlessEnvironment } = require('../../dd-trace/src/serverless')
 
 if (globalThis.fetch) {
-  const ch = tracingChannel('apm:fetch:request')
-  const wrapFetch = createWrapFetch(globalThis.Request, ch, () => {
-    channel('dd-trace:instrumentation:load').publish({ name: 'fetch' })
-  })
+  const globalFetch = globalThis.fetch
 
-  globalThis.fetch = shimmer.wrapFunction(fetch, fetch => wrapFetch(fetch))
+  let fetch = (input, init) => {
+    wrapRealFetch()
+
+    return fetch(input, init)
+  }
+
+  function wrapRealFetch () {
+    const { channel, tracingChannel } = require('dc-polyfill')
+    const { createWrapFetch } = require('./helpers/fetch')
+
+    const ch = tracingChannel('apm:fetch:request')
+    const wrapFetch = createWrapFetch(globalThis.Request, ch, () => {
+      channel('dd-trace:instrumentation:load').publish({ name: 'fetch' })
+    })
+
+    fetch = wrapFetch(globalFetch)
+  }
+
+  if (!isInServerlessEnvironment()) {
+    wrapRealFetch()
+  }
+
+  globalThis.fetch = function value (input, init) {
+    return fetch(input, init)
+  }
 }
diff --git a/packages/dd-trace/src/config.js b/packages/dd-trace/src/config.js
@@ -16,7 +16,7 @@ const { GIT_REPOSITORY_URL, GIT_COMMIT_SHA } = require('./plugins/util/tags')
 const { getGitMetadataFromGitProperties, removeUserSensitiveInfo } = require('./git_properties')
 const { updateConfig } = require('./telemetry')
 const telemetryMetrics = require('./telemetry/metrics')
-const { getIsGCPFunction, getIsAzureFunction } = require('./serverless')
+const { isInServerlessEnvironment, getIsGCPFunction, getIsAzureFunction } = require('./serverless')
 const { ORIGIN_KEY, GRPC_CLIENT_ERROR_STATUSES, GRPC_SERVER_ERROR_STATUSES } = require('./constants')
 const { appendRules } = require('./payload-tagging/config')
 
@@ -419,10 +419,7 @@ class Config {
   }
 
   _isInServerlessEnvironment () {
-    const inAWSLambda = process.env.AWS_LAMBDA_FUNCTION_NAME !== undefined
-    const isGCPFunction = getIsGCPFunction()
-    const isAzureFunction = getIsAzureFunction()
-    return inAWSLambda || isGCPFunction || isAzureFunction
+    return isInServerlessEnvironment()
   }
 
   // for _merge to work, every config value must have a default value
diff --git a/packages/dd-trace/src/serverless.js b/packages/dd-trace/src/serverless.js
@@ -60,9 +60,18 @@ function getIsAzureFunction () {
   return isAzureFunction
 }
 
+function isInServerlessEnvironment () {
+  const inAWSLambda = process.env.AWS_LAMBDA_FUNCTION_NAME !== undefined
+  const isGCPFunction = getIsGCPFunction()
+  const isAzureFunction = getIsAzureFunction()
+
+  return inAWSLambda || isGCPFunction || isAzureFunction
+}
+
 module.exports = {
   maybeStartServerlessMiniAgent,
   getIsGCPFunction,
   getIsAzureFunction,
-  getRustBinaryPath
+  getRustBinaryPath,
+  isInServerlessEnvironment
 }
