fetch jobs from queues concurrently

src/client.ts

@@ -143,14 +143,23 @@ export default class RiverClient<D extends Driver<Tx>, Tx> {
 
   private async fetchAndWork(): Promise<boolean> {
     const queues = Object.entries(this.configuration.queues ?? {});
-    let hasFullBatch = false;
-
-    for (const [queue, queueConfig] of queues) {
+    const queueFetches = queues.flatMap(([queue, queueConfig]) => {
       const running = this.running.get(queue) ?? 0;
       const slots = queueConfig.concurrency - running;
-      if (slots <= 0) continue;
+      if (slots <= 0) return [];
+
+      return [
+        this.driver.getAvailableJobs(queue, slots, this.clientId).then((jobs) => ({
+          jobs,
+          slots,
+        })),
+      ];
+    });
+
+    const queueResults = await Promise.all(queueFetches);
+    let hasFullBatch = false;
 
-      const jobs = await this.driver.getAvailableJobs(queue, slots, this.clientId);
+    for (const { jobs, slots } of queueResults) {
       if (jobs.length === slots) hasFullBatch = true;
 
       for (const job of jobs) {

test/node-river/unit/client.test.ts

@@ -140,6 +140,34 @@ describe('RiverClient worker', () => {
     expect(driver.getAvailableJobs).toHaveBeenCalledWith('default', 5, expect.any(String));
   });
 
+  it('polls multiple queues in parallel', async () => {
+    client = new RiverClient(driver, {
+      queues: {
+        default: { concurrency: 2 },
+        urgent: { concurrency: 3 },
+      },
+      pollInterval: 60_000,
+    });
+
+    let resolveDefaultQueue: (jobs: Job[]) => void;
+    const defaultQueue = new Promise<Job[]>((resolve) => {
+      resolveDefaultQueue = resolve;
+    });
+
+    (driver.getAvailableJobs as jest.Mock).mockImplementation((queue: string) => {
+      if (queue === 'default') return defaultQueue;
+      return Promise.resolve([]);
+    });
+
+    client.work();
+    await flushPromises();
+
+    expect(driver.getAvailableJobs).toHaveBeenCalledWith('default', 2, expect.any(String));
+    expect(driver.getAvailableJobs).toHaveBeenCalledWith('urgent', 3, expect.any(String));
+
+    resolveDefaultQueue!([]);
+  });
+
   it('processes multiple jobs from the same poll concurrently', async () => {
     const jobs = [makeJob({ id: 1 }), makeJob({ id: 2 })];
     (driver.getAvailableJobs as jest.Mock).mockResolvedValueOnce(jobs);