How to return an error from a child

[ryandesign]

Could you add an example showing how to return an error from a child? I'm trying to call the callback function with a new Error('...') object in the first parameter as usual, but although the master process recognizes that there's something in err, it appears to be an empty object, so I can't get any details about the error that occurred.

This is with node 0.10.12 on OS X 10.8.4.

[rvagg]

@ryandesign fyi I've seen the issues you've submitted here and I'd love to address them but I'm a little busy right at this moment but I will get to them! You're welcome to open pull requests to try and deal with the things you've raised and I'm happy to steer you through the process of getting it right.

[ryandesign]

According to a comment in nodejs/node-v0.x-archive#5727 the communication channel employed by process.send() converts everything to JSON first. So custom object types (like Errors) can't possibly work, since object types aren't represented in JSON. And this pretty much invalidates worker-farm's promise to pass along the arguments unchanged.

[ryandesign]

So there seem to be two problems.

1. Since process.send() uses JSON, any object you send will become a generic object. This can be addressed by making "reviver" functions, but these seem to require some participation of the particular object types being revived; developers using worker-farm would have to be aware of this requirement and provide for it. Or worker-farm could try to install private revivers into each type of object being used, but these wouldn't work in all cases.
2. The Error object does not serialize to JSON properly. See JSON.stringify(new Error('hello')). I don't know if this is considered a bug or a feature.

[rvagg]

suggestions for solutions?

[rvagg]

fixed by doing a custom serialisation and deserialisation of Error objects.