From a71b9505ea76596659c98eb6180a09a895399741 Mon Sep 17 00:00:00 2001
From: Mohamed Bassem <me@mbassem.com>
Date: Sun, 30 Nov 2025 00:19:28 +0000
Subject: fix: Add restate queued idempotency (#2169)

* fix: Add restate queued idempotency

* return on failed to acquire
---
 packages/plugins/queue-restate/src/index.ts        |  3 +-
 packages/plugins/queue-restate/src/semaphore.ts    | 36 ++++++++++++++++++++--
 packages/plugins/queue-restate/src/service.ts      | 10 +++++-
 .../plugins/queue-restate/src/tests/queue.test.ts  | 21 +++++++++++++
 4 files changed, 65 insertions(+), 5 deletions(-)

(limited to 'packages/plugins/queue-restate')

diff --git a/packages/plugins/queue-restate/src/index.ts b/packages/plugins/queue-restate/src/index.ts
index de37bbea..fa636f87 100644
--- a/packages/plugins/queue-restate/src/index.ts
+++ b/packages/plugins/queue-restate/src/index.ts
@@ -42,6 +42,7 @@ class RestateQueueWrapper<T> implements Queue<T> {
           payload: T;
           priority: number;
           groupId?: string;
+          queuedIdempotencyKey?: string;
         },
       ) => Promise<void>;
     }
@@ -51,6 +52,7 @@ class RestateQueueWrapper<T> implements Queue<T> {
         payload,
         priority: options?.priority ?? 0,
         groupId: options?.groupId,
+        queuedIdempotencyKey: options?.idempotencyKey,
       },
       restateClient.rpc.sendOpts({
         delay: options?.delayMs
@@ -58,7 +60,6 @@ class RestateQueueWrapper<T> implements Queue<T> {
               milliseconds: options.delayMs,
             }
           : undefined,
-        idempotencyKey: options?.idempotencyKey,
       }),
     );
     return res.invocationId;
diff --git a/packages/plugins/queue-restate/src/semaphore.ts b/packages/plugins/queue-restate/src/semaphore.ts
index 9acecf28..694c77b3 100644
--- a/packages/plugins/queue-restate/src/semaphore.ts
+++ b/packages/plugins/queue-restate/src/semaphore.ts
@@ -5,6 +5,7 @@ import { Context, object, ObjectContext } from "@restatedev/restate-sdk";
 
 interface QueueItem {
   awakeable: string;
+  idempotencyKey?: string;
   priority: number;
 }
 
@@ -35,9 +36,18 @@ export const semaphore = object({
         priority: number;
         capacity: number;
         groupId?: string;
+        idempotencyKey?: string;
       },
-    ): Promise<void> => {
+    ): Promise<boolean> => {
       const state = await getState(ctx);
+
+      if (
+        req.idempotencyKey &&
+        idempotencyKeyAlreadyExists(state.groups, req.idempotencyKey)
+      ) {
+        return false;
+      }
+
       req.groupId = req.groupId ?? "__ungrouped__";
 
       if (state.groups[req.groupId] === undefined) {
@@ -51,11 +61,13 @@ export const semaphore = object({
       state.groups[req.groupId].items.push({
         awakeable: req.awakeableId,
         priority: req.priority,
+        idempotencyKey: req.idempotencyKey,
       });
 
       tick(ctx, state, req.capacity);
 
       setState(ctx, state);
+      return true;
     },
 
     release: async (
@@ -149,6 +161,18 @@ async function getState(
   };
 }
 
+function idempotencyKeyAlreadyExists(
+  items: Record<string, GroupState>,
+  key: string,
+) {
+  for (const group of Object.values(items)) {
+    if (group.items.some((item) => item.idempotencyKey === key)) {
+      return true;
+    }
+  }
+  return false;
+}
+
 function setState(ctx: ObjectContext<LegacyQueueState>, state: QueueState) {
   ctx.set("itemsv2", state.groups);
   ctx.set("inFlight", state.inFlight);
@@ -162,17 +186,22 @@ export class RestateSemaphore {
     private readonly capacity: number,
   ) {}
 
-  async acquire(priority: number, groupId?: string) {
+  async acquire(priority: number, groupId?: string, idempotencyKey?: string) {
     const awk = this.ctx.awakeable();
-    await this.ctx
+    const res = await this.ctx
       .objectClient<typeof semaphore>({ name: "Semaphore" }, this.id)
       .acquire({
         awakeableId: awk.id,
         priority,
         capacity: this.capacity,
         groupId,
+        idempotencyKey,
       });
 
+    if (!res) {
+      return false;
+    }
+
     try {
       await awk.promise;
     } catch (e) {
@@ -181,6 +210,7 @@ export class RestateSemaphore {
         throw e;
       }
     }
+    return true;
   }
   async release() {
     await this.ctx
diff --git a/packages/plugins/queue-restate/src/service.ts b/packages/plugins/queue-restate/src/service.ts
index b26f66cf..5ba7d1df 100644
--- a/packages/plugins/queue-restate/src/service.ts
+++ b/packages/plugins/queue-restate/src/service.ts
@@ -39,6 +39,7 @@ export function buildRestateService<T, R>(
         ctx: restate.Context,
         data: {
           payload: T;
+          queuedIdempotencyKey?: string;
           priority: number;
           groupId?: string;
         },
@@ -65,7 +66,14 @@ export function buildRestateService<T, R>(
 
         let lastError: Error | undefined;
         for (let runNumber = 0; runNumber <= NUM_RETRIES; runNumber++) {
-          await semaphore.acquire(priority, data.groupId);
+          const acquired = await semaphore.acquire(
+            priority,
+            data.groupId,
+            data.queuedIdempotencyKey,
+          );
+          if (!acquired) {
+            return;
+          }
           const res = await runWorkerLogic(ctx, funcs, {
             id,
             data: payload,
diff --git a/packages/plugins/queue-restate/src/tests/queue.test.ts b/packages/plugins/queue-restate/src/tests/queue.test.ts
index 28e32394..2085d57b 100644
--- a/packages/plugins/queue-restate/src/tests/queue.test.ts
+++ b/packages/plugins/queue-restate/src/tests/queue.test.ts
@@ -209,9 +209,30 @@ describe("Restate Queue Provider", () => {
   it("should use idempotency key", async () => {
     const idempotencyKey = `test-${Date.now()}`;
 
+    // hog the queue
+    await Promise.all([
+      queue.enqueue(
+        { type: "semaphore-acquire" },
+        { groupId: "init", priority: -10 },
+      ),
+      queue.enqueue(
+        { type: "semaphore-acquire" },
+        { groupId: "init", priority: -10 },
+      ),
+      queue.enqueue(
+        { type: "semaphore-acquire" },
+        { groupId: "init", priority: -10 },
+      ),
+    ]);
+    await testState.baton.waitUntilCountWaiting(3);
+
     await queue.enqueue({ type: "val", val: 200 }, { idempotencyKey });
     await queue.enqueue({ type: "val", val: 200 }, { idempotencyKey });
 
+    await new Promise((resolve) => setTimeout(resolve, 1000));
+
+    testState.baton.release();
+
     await waitUntilQueueEmpty();
 
     expect(testState.results).toEqual([200]);
-- 
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