feat(queue): add getRateLimitTtl method (#2105)

src/classes/queue-getters.ts

@@ -105,6 +105,17 @@ export class QueueGetters<
     return count;
   }
 
+  /**
+   * Returns the time to live for a rate limited key in milliseconds.
+   * @returns -2 if the key does not exist.
+   * @returns -1 if the key exists but has no associated expire.
+   * @see {@link https://redis.io/commands/pttl/}
+   */
+  async getRateLimitTtl(): Promise<number> {
+    const client = await this.client;
+    return client.pttl(this.keys.limiter);
+  }
+
   /**
    * Job counts by type
    *

tests/test_rate_limiter.ts

@@ -330,11 +330,17 @@ describe('Rate Limiter', function () {
       const duration = 100;
       const margin = 0.95; // 5% margin for CI
 
+      const ttl = await queue.getRateLimitTtl();
+      expect(ttl).to.be.equal(-2);
+
       const worker = new Worker(
         queueName,
         async job => {
           if (job.attemptsMade === 1) {
             await worker.rateLimit(dynamicLimit);
+            const currentTtl = await queue.getRateLimitTtl();
+            expect(currentTtl).to.be.lessThanOrEqual(250);
+            expect(currentTtl).to.be.greaterThan(100);
             throw Worker.RateLimitError();
           }
         },