fix: exposed preload flags in debug mode (#1268)

refs INSTA-778

Author: abhilash-sivan

packages/core/src/tracing/index.js

@@ -22,6 +22,7 @@ const {
   isESMApp
 } = require('../util/esm');
 const iitmHook = require('../util/iitmHook');
+const { getPreloadFlags } = require('../util/getPreloadFlags');
 
 let tracingEnabled = false;
 let tracingActivated = false;
@@ -180,6 +181,13 @@ exports.preInit = function preInit(preliminaryConfig) {
  * @param {CollectorPIDStore} _processIdentityProvider
  */
 exports.init = function init(_config, downstreamConnection, _processIdentityProvider) {
+  if (process.env.INSTANA_DEBUG || process.env.INSTANA_LOG_LEVEL === 'debug') {
+    const preloadFlags = getPreloadFlags();
+
+    // eslint-disable-next-line no-console
+    console.debug(`The App is using the following preload flags: ${preloadFlags}`);
+  }
+
   // Consider removing this in the next major release(v4.x) of the @instana package.
   if (hasExperimentalLoaderFlag()) {
     // eslint-disable-next-line no-console

packages/core/src/util/getPreloadFlags.js

@@ -0,0 +1,50 @@
+/*
+ * (c) Copyright IBM Corp. 2024
+ */
+
+'use strict';
+
+/** @type {import('../logger').GenericLogger} */
+let logger;
+logger = require('../logger').getLogger('util/getPreloadFlags', newLogger => {
+  logger = newLogger;
+});
+
+exports.getPreloadFlags = function getPreloadFlags() {
+  const flags = ['--require', '--import', '--experimental-loader'];
+
+  /**
+   * @param {string[]} optionArray
+   */
+  function extractOption(optionArray) {
+    const relevantOptions = [];
+
+    for (let i = 0; i < optionArray.length; i++) {
+      if (flags.some(flag => optionArray[i].includes(flag))) {
+        relevantOptions.push(`${optionArray[i]} ${optionArray[i + 1]}`);
+        i++;
+      }
+    }
+
+    return relevantOptions.join(', ');
+  }
+
+  try {
+    let nodeOptions = '';
+    if (process.env.NODE_OPTIONS) {
+      const nodeOptionsArray = process.env.NODE_OPTIONS.split(' ');
+      nodeOptions = extractOption(nodeOptionsArray);
+    }
+
+    let execArgs = '';
+    if (process.execArgv.length > 0) {
+      execArgs = extractOption(process.execArgv);
+    }
+
+    const result = [nodeOptions, execArgs].filter(Boolean).join(', ') || 'noFlags';
+    return result;
+  } catch (error) {
+    logger.error('Error occurred while doing preload flag filtering: %s ', error);
+    return '';
+  }
+};

packages/core/test/util/getPreloadFlags_test.js

@@ -0,0 +1,75 @@
+/*
+ * (c) Copyright IBM Corp. 2024
+ */
+
+'use strict';
+
+const expect = require('chai').expect;
+
+const { getPreloadFlags } = require('../../src/util/getPreloadFlags');
+
+describe('util.getPreloadFlags', () => {
+  const originalNodeOptions = process.env.NODE_OPTIONS;
+  const originalExecArgv = process.execArgv.slice();
+
+  const resetEnvironment = () => {
+    process.env.NODE_OPTIONS = '';
+    process.execArgv = [];
+  };
+
+  beforeEach(() => {
+    resetEnvironment();
+  });
+
+  afterEach(() => {
+    resetEnvironment();
+  });
+
+  after(() => {
+    process.env.NODE_OPTIONS = originalNodeOptions;
+    process.execArgv = originalExecArgv;
+  });
+
+  it('should return relevant flags from NODE_OPTIONS', () => {
+    process.env.NODE_OPTIONS =
+      "INSTANA_DEBUG=true node --require '@instana/collector/src/immediate.js' ./dummy-app/src/index.js";
+
+    const result = getPreloadFlags();
+
+    expect(result).equal("--require '@instana/collector/src/immediate.js'");
+  });
+
+  it('should return relevant flags from execArgv', () => {
+    process.execArgv = ['--require', '@instana/collector/src/immediate.js'];
+
+    const result = getPreloadFlags();
+
+    expect(result).equal('--require @instana/collector/src/immediate.js');
+  });
+
+  it('should return relevant flags from both NODE_OPTIONS and execArgv', () => {
+    process.env.NODE_OPTIONS = '--require /path/to/some/file';
+    process.execArgv = ['--import', '/path/to/instana/node_modules/@instana/collector/esm-register.mjs'];
+
+    const result = getPreloadFlags();
+
+    expect(result).equal(
+      '--require /path/to/some/file, --import /path/to/instana/node_modules/@instana/collector/esm-register.mjs'
+    );
+  });
+
+  it('should return "noFlags" when no relevant flags are found', () => {
+    process.env.NODE_OPTIONS = '--inspect value';
+    process.execArgv = ['--anotherFlag', 'value'];
+
+    const result = getPreloadFlags();
+
+    expect(result).equal('noFlags');
+  });
+
+  it('should return "noFlags" when NODE_OPTIONS and execArgv are empty', () => {
+    const result = getPreloadFlags();
+
+    expect(result).equal('noFlags');
+  });
+});