debug warnings when init after instrumented modules

packages/datadog-core/src/utils/src/extract-package-and-module-path.js

@@ -0,0 +1,33 @@
+'use strict'
+
+const NM = 'node_modules/'
+
+/**
+ * For a given full path to a module,
+ *   return the package name it belongs to and the local path to the module
+ *   input: '/foo/node_modules/@co/stuff/foo/bar/baz.js'
+ *   output: { pkg: '@co/stuff', path: 'foo/bar/baz.js' }
+ */
+module.exports = function extractPackageAndModulePath (fullPath) {
+  const nm = fullPath.lastIndexOf(NM)
+  if (nm < 0) {
+    return { pkg: null, path: null }
+  }
+
+  const subPath = fullPath.substring(nm + NM.length)
+  const firstSlash = subPath.indexOf('/')
+
+  if (subPath[0] === '@') {
+    const secondSlash = subPath.substring(firstSlash + 1).indexOf('/')
+
+    return {
+      pkg: subPath.substring(0, firstSlash + 1 + secondSlash),
+      path: subPath.substring(firstSlash + 1 + secondSlash + 1)
+    }
+  }
+
+  return {
+    pkg: subPath.substring(0, firstSlash),
+    path: subPath.substring(firstSlash + 1)
+  }
+}

packages/datadog-esbuild/index.js

@@ -4,6 +4,7 @@
 
 const instrumentations = require('../datadog-instrumentations/src/helpers/instrumentations.js')
 const hooks = require('../datadog-instrumentations/src/helpers/hooks.js')
+const extractPackageAndModulePath = require('../datadog-core/src/utils/src/extract-package-and-module-path')
 
 for (const hook of Object.values(hooks)) {
   hook()
@@ -21,7 +22,6 @@ for (const instrumentation of Object.values(instrumentations)) {
   }
 }
 
-const NM = 'node_modules/'
 const INSTRUMENTED = Object.keys(instrumentations)
 const RAW_BUILTINS = require('module').builtinModules
 const CHANNEL = 'dd-trace:bundler:load'
@@ -181,33 +181,3 @@ function dotFriendlyResolve (path, directory) {
 
   return require.resolve(path, { paths: [directory] })
 }
-
-/**
- * For a given full path to a module,
- *   return the package name it belongs to and the local path to the module
- *   input: '/foo/node_modules/@co/stuff/foo/bar/baz.js'
- *   output: { pkg: '@co/stuff', path: 'foo/bar/baz.js' }
- */
-function extractPackageAndModulePath (fullPath) {
-  const nm = fullPath.lastIndexOf(NM)
-  if (nm < 0) {
-    return { pkg: null, path: null }
-  }
-
-  const subPath = fullPath.substring(nm + NM.length)
-  const firstSlash = subPath.indexOf('/')
-
-  if (subPath[0] === '@') {
-    const secondSlash = subPath.substring(firstSlash + 1).indexOf('/')
-
-    return {
-      pkg: subPath.substring(0, firstSlash + 1 + secondSlash),
-      path: subPath.substring(firstSlash + 1 + secondSlash + 1)
-    }
-  }
-
-  return {
-    pkg: subPath.substring(0, firstSlash),
-    path: subPath.substring(firstSlash + 1)
-  }
-}

packages/dd-trace/src/check_require_cache.js

@@ -0,0 +1,39 @@
+'use strict'
+
+const extractPackageAndModulePath = require('../../datadog-core/src/utils/src/extract-package-and-module-path')
+
+/**
+ * The lowest hanging fruit to debug an app that isn't tracing
+ * properly is to check that it is loaded before any modules
+ * that need to be instrumented. This function checks the
+ * `require.cache` to see if any instrumented modules have been
+ * required already and prints a warning.
+ *
+ * Note that this only going to work for modules within npm
+ * packages, like `express`, and not internal modules, like
+ * `http`.
+ *
+ * The output isn't necessarily 100% perfect. For example if the
+ * app loads a package we instrument but outside of an
+ * unsupported version then a warning would still be displayed.
+ * This is OK as the tracer should be loaded earlier regardless.
+ */
+module.exports = function () {
+  const packages = require('../../datadog-instrumentations/src/helpers/hooks')
+  const naughties = new Set()
+  let didWarn = false
+
+  for (let pathToModule of Object.keys(require.cache)) {
+    const { pkg } = extractPackageAndModulePath(pathToModule)
+
+    if (naughties.has(pkg)) continue
+    if (!(pkg in packages)) continue
+
+    console.error(`Warning: The package '${pkg}' was loaded before dd-trace! This may cause errors with instrumentation`)
+
+    naughties.add(pkg)
+    didWarn = true
+  }
+
+  if (didWarn) console.error(`Warning: Please ensure dd-trace is loaded before any other modules to ensure proper functionality`)
+}

packages/dd-trace/src/proxy.js

@@ -15,6 +15,7 @@ const NoopDogStatsDClient = require('./noop/dogstatsd')
 const spanleak = require('./spanleak')
 const { SSITelemetry } = require('./profiling/ssi-telemetry')
 const telemetryLog = require('dc-polyfill').channel('datadog:telemetry:log')
+const checkRequireCache = require('./check_require_cache')
 
 class LazyModule {
   constructor (provider) {
@@ -55,8 +56,11 @@ class Tracer extends NoopProxy {
 
     try {
       const config = new Config(options) // TODO: support dynamic code config
+
       telemetry.start(config, this._pluginManager)
 
+      if (config.debug) checkRequireCache()
+
       if (config.dogstatsd) {
         // Custom Metrics
         this.dogstatsd = new dogstatsd.CustomMetrics(config)