UnhandledPromiseRejection on connection error.

[jan-osch]

I am getting an UnhandledPromiseRejectionWarning when ECONNREFUSED is thrown on initial connection.

const Queue = require('bull');

const q = new Queue('test', 'redis://localhost:8009'); // no redis instance here

q.on('error', e => console.error('Error event', e.message));

q.process('task', 1, (job) => {
  console.log('ok');
  return Promise.resolve(job.id);
})
 .catch(error => console.error('Failed to start consumer', error.message));

I am getting this output:

Error event connect ECONNREFUSED 127.0.0.1:8009
Error event Error initializing Lua scripts
Failed to start processing connect ECONNREFUSED 127.0.0.1:8009
(node:12173) UnhandledPromiseRejectionWarning: Error: connect ECONNREFUSED 127.0.0.1:8009
    at TCPConnectWrap.afterConnect [as oncomplete] (net.js:1137:16)
(node:12173) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). To terminate the node process on unhandled promise rejection, use the CLI flag `--unhandled-rejections=strict` (see https://nodejs.org/api/cli.html#cli_unhandled_rejections_mode). (rejection id: 1)
(node:12173) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.
Error event connect ECONNREFUSED 127.0.0.1:8009
Error event connect ECONNREFUSED 127.0.0.1:8009

How can I handle the UnhandledPromiseRejectionWarning error ?

[cfey]

Hi @jan-osch,
I got the same error
I fixed it by removing
global.Promise = require('bluebird');
This were declared somewhere in my project, without this global Promise override everything works as expected.

Let me know if this fixed your issue :)

Cheers

[jan-osch]

@cfey
Hey - thanks for checking that out. I don't override promises anywhere in the project. The sample code I provided is a single isolated file that I use to reproduce the issue.

I can confirm that the issue still exists.
Node version: v12.16.0
Bull 3.13.0

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[lamai6]

I still get this error but I find a (maybe ?) cleaner solution to fix that annoying warning by using Promise.

Solution

queue.isReady()
.then(() => {
    queue.process(function (job, done) {
        myFunction(...);
        done();
    });
})
.catch((err) => {
    console.error(`Error ${err.errno} : ${err.message}`);
    // If redis instance is not started, you can also stop your server
    // process.exit(1);
});

Result

If Redis instance is not started, instead of getting a UnhandledPromiseRejectionWarning, you will get an error in your console with my example :

Versions

{
    "nodejs": "14.15.0",
    "bull": "3.27.0"
}