nats.js/jetstream/examples/03_batch.js

/*
 * Copyright 2023 The NATS Authors
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import { connect } from "@nats-io/transport-deno";
import { jetstream } from "@nats-io/jetstream";
import { setupStreamAndConsumer } from "./util.js";

// create a connection
const nc = await connect();

// create a stream with a random name with some messages and a consumer
const { stream, consumer } = await setupStreamAndConsumer(nc, 10);

// retrieve an existing consumer
const js = jetstream(nc);
const c = await js.consumers.get(stream, consumer);

// with fetch the consumer can manually control the buffering
for (let i = 0; i < 3; i++) {
  const messages = await c.fetch({ max_messages: 4, expires: 2000 });
  for await (const m of messages) {
    m.ack();
  }
  console.log(`batch completed: ${messages.getProcessed()} msgs processed`);
}

await nc.close();