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06_heartbeats.ts
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06_heartbeats.ts
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/*
* 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, ConsumerEvents } from "../../src/mod.ts";
import { setupStreamAndConsumer } from "./util.ts";
// 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);
// retrieve an existing consumer
const js = nc.jetstream();
const c = await js.consumers.get(stream, consumer);
while (true) {
const messages = await c.consume({ max_messages: 1 });
// watch the to see if the consume operation misses heartbeats
(async () => {
for await (const s of await messages.status()) {
if (s.type === ConsumerEvents.HeartbeatsMissed) {
// you can decide how many heartbeats you are willing to miss
const n = s.data as number;
console.log(`${n} heartbeats missed`);
if (n === 2) {
// by calling `stop()` the message processing loop ends.
// in this case this is wrapped by a loop, so it attempts
// to re-setup the consume
messages.stop();
}
}
}
})();
for await (const m of messages) {
console.log(`${m.seq} ${m?.subject}`);
m.ack();
}
}