chore: add optional boolean to force InvokeStoreMulti

.changeset/fair-dolls-smash.md

@@ -0,0 +1,5 @@
+---
+"@aws/lambda-invoke-store": patch
+---
+
+Added an optional boolean argument that allows forcing the use of InvokeStoreMulti with AsyncLocalStorage.

src/invoke-store.force-multi.spec.ts

@@ -0,0 +1,9 @@
+import { describe, it, expect } from "vitest";
+import { InvokeStore } from "./invoke-store.js";
+
+describe("forceInvokeStoreMulti", () => {
+  it("should create InvokeStoreMulti when forceInvokeStoreMulti is true, without env var", async () => {
+    const store = await InvokeStore.getInstanceAsync(true);
+    expect(store.constructor.name).toBe("InvokeStoreMulti");
+  });
+});

src/invoke-store.ts

@@ -152,11 +152,11 @@ class InvokeStoreMulti extends InvokeStoreBase {
 export namespace InvokeStore {
   let instance: Promise<InvokeStoreBase> | null = null;
 
-  export async function getInstanceAsync(): Promise<InvokeStoreBase> {
+  export async function getInstanceAsync(forceInvokeStoreMulti?: boolean): Promise<InvokeStoreBase> {
     if (!instance) {
       // Lock synchronously on first invoke by immediately assigning the promise
       instance = (async () => {
-        const isMulti = "AWS_LAMBDA_MAX_CONCURRENCY" in process.env;
+        const isMulti = forceInvokeStoreMulti === true || "AWS_LAMBDA_MAX_CONCURRENCY" in process.env;
         const newInstance = isMulti
           ? await InvokeStoreMulti.create()
           : new InvokeStoreSingle();