Prevent agent from starting twice in edge case

Author: timokoessler

library/helpers/indexImportGuard.test.ts

@@ -0,0 +1,42 @@
+import * as t from "tap";
+import { wrap } from "./wrap";
+
+const logs: string[] = [];
+wrap(console, "error", function warn() {
+  return function error(message: string) {
+    logs.push(message);
+  };
+});
+wrap(console, "log", function warn() {
+  return function log(message: string) {
+    logs.push(message);
+  };
+});
+
+t.test("it works", async (t) => {
+  process.env.AIKIDO_DEBUG = "true";
+  process.env.AIKIDO_BLOCK = "false";
+
+  t.same(logs, []);
+  require("../index");
+  t.same(logs, [
+    "AIKIDO: Starting agent v0.0.0...",
+    "AIKIDO: Dry mode enabled, no requests will be blocked!",
+    "AIKIDO: No token provided, disabling reporting.",
+    "AIKIDO: Running in monitoring only mode without reporting to Aikido Cloud. Set AIKIDO_BLOCK=true to enable blocking.",
+  ]);
+
+  // Clear logs
+  logs.length = 0;
+
+  // Clear require cache
+  for (const path in require.cache) {
+    delete require.cache[path];
+  }
+
+  require("../index");
+
+  t.same(logs, [
+    "AIKIDO: Zen has already been initialized. Please ensure that Zen is imported only once in your application, as importing it multiple times can lead to unexpected behavior.",
+  ]);
+});

library/helpers/indexImportGuard.ts

@@ -0,0 +1,19 @@
+const symbol = Symbol.for("zen.nodejs.index.run.once");
+
+export function checkIndexImportGuard(): boolean {
+  const globalState = globalThis as typeof globalThis & {
+    [symbol]: boolean;
+  };
+
+  if (globalState[symbol]) {
+    // eslint-disable-next-line no-console
+    console.error(
+      "AIKIDO: Zen has already been initialized. Please ensure that Zen is imported only once in your application, as importing it multiple times can lead to unexpected behavior."
+    );
+
+    return false;
+  }
+
+  globalState[symbol] = true;
+  return true;
+}

library/index.ts

@@ -10,11 +10,13 @@ import { addHapiMiddleware } from "./middleware/hapi";
 import { addFastifyHook } from "./middleware/fastify";
 import { addKoaMiddleware } from "./middleware/koa";
 import { isESM } from "./helpers/isESM";
+import { checkIndexImportGuard } from "./helpers/indexImportGuard";
 
 const supported = isFirewallSupported();
 const shouldEnable = shouldEnableFirewall();
+const notAlreadyImported = checkIndexImportGuard();
 
-if (supported && shouldEnable) {
+if (supported && shouldEnable && notAlreadyImported) {
   if (isESM()) {
     console.warn(
       "AIKIDO: Your application seems to be running in ESM mode. Zen does not support ESM at runtime yet."