Primus and async plugins

Question

Version: 8.0.3

Environment:

• Operating system: macOS Big Sur 11.5.2
• Browser: Google Chrome Version 92.0.4515.159 (Official Build) (x86_64)
• Node.js: 13.14.0

Hi,

I'm using Primus with websockets and I'm wondering if it supports async plugins. I looked at Primus docs but I didn't find what I need.

Basically I'm trying to pass an async function into Primus constructor like this:

 this.primus = new Primus(server, {
      pathname: '/my-path', plugin: {
        'my-validator': {
          server: myAsyncPlugin //this should run only on the server
        }
      }
    });

The issue is that if I register plugin like that, it does not work and my plugin is always called after other handlers but I want it to be executed before other stuff happens as it validates some incoming parameters. (I also looked at middleware but I couldn't get it working)

So if I register my plugin in constructor and then do the following, my plugin will not work:

this.primus.on('connection', (spark) => {
      //...do stuff
 });

But if I remove plugin from constructor and use following code, everything works as expected as I'm using an async function like so:

this.primus.on('connection', async (spark) => {
      //await myPlugin.doStuff();
      //other stuff
});

And here's how example plugin code looks like:

public doPluginStuff = (primus, options) => {
        primus.on('connection', async (spark) => {
            await exectuteAsyncStuffHere();
        });
    };

So I'm curious if there's a way to achieve what I need or do I have to call my plugin directly in the 'connection' handler.

Thanks!

Answer 1

Problem clarified and solved as per this GitHub issue.

Basically it's better to use middleware for such issues (incoming parameters validation) and it can be done like this:

this.primus.use(() => {
      return async (req, res, next) => {

        try {
          if (!await doStuff()) {
            res.destroy();
            return;
          }
        } catch (error) {
          res.destroy();
          return;
        }

        next();
      }
    });

Also this plugin was given to my by the lib maintainer as an example of async plugin implementation, maybe it will be helpful to someone else.