[I] Producers or consumers may be closed after the client exits out of scope [pulsar-client-node]

["RobertIndie (via GitHub)" <gi...@apache.org>]

RobertIndie opened a new issue, #399:
URL: https://github.com/apache/pulsar-client-node/issues/399

   Here is the reproduction code:
   ```js
   const Pulsar = require('pulsar-client');
   
   (async () => {
     // Create a client
     const client = new Pulsar.Client({
       serviceUrl: 'pulsar://localhost:6650'
     });
   
     // Create a producer
     const producer = await client.createProducer({
       topic: 'persistent://public/default/my-topic',
     });
     
     const sendRecords = async () => {
       // Send a message
       await producer.send({
           data: Buffer.from("hello")
       });
   
       console.log("sent hello")
       setTimeout(()=>sendRecords(), 1000)
     }
   
     
     await sendRecords();
   })();
   ```
   
   The output would be like:
   ```
   ➜  node node index.js
   sent hello
   sent hello
   sent hello
   sent hello
   sent hello
   sent hello
   sent hello
   node:internal/process/promises:288
               triggerUncaughtException(err, true /* fromPromise */);
               ^
   
   [Error: Failed to send message: AlreadyClosed]
   
   Node.js v18.19.0
   ```
   After the client exits the outer function's scope, it will eventually be garbage collected. This closes the producers and causes the AlreadyClosed issue.
   
   A workaround is to pass the client ref to the sendRecords function:
   ```js
     const sendRecords = async (client) => {
       // Send a message
       await producer.send({
           data: Buffer.from("hello")
       });
   
       console.log("sent hello")
       setTimeout(()=>sendRecords(client), 1000)
     }
   
     
     await sendRecords(client);
   ```
   
   And it works.
   
   A better approach is to keep a reference to the client inside the producer or consumer. This way, as long as we hold a reference to the producer or consumer, the client object will not be garbage collected.


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