onSend hook not being called on web socket route

[michele-tonizzo]

Hello,

I'm filtering the data returning from a route before being sent back to the client using onSend hook and works as expected

fastify.addHook("onSend", (request, reply, payload, next) => {
    const mask = request?.query?.["mask"];

   // ...

    const filtered = applyMask(object, mask);

    return next(null, JSON.stringify(filtered));
  });

  return next();
};

I also have web socket connections in my API that I would like behave the same before sending the message to the client but apparently, even if the in documentation of @fastify/websocket it states that "it will run any hooks that have been registered", it does not apply to onSend hook when sending back using connection

connection.socket.send(JSON.stringify(data));

From testing the hook is not called entirely.

Is this the correct behaviour? How can I achieve the same result that I have using HTTP methods?

Thanks

[mcollina]

The documentation is incorrect and onSend will not be called.

[Ekott2006]

Hello, can i try to fix this issue??

[airhorns]

@Ekott2006 I don't think it really makes sense to call the onSend hook, as the webhook can send and receive data many times, unlike a normal request. I think the right resolution here is to update the documentation to describe which hooks do run and which are skipped once the request has been upgraded to a websocket.

[Uzlopak]

I guess, we would need to implement a new "hook" stage like calling it "onWebsocketSend". And then handle the "hooks" before calling the webhook handler here.

fastify-websocket/index.js

Line 141 in ec0e7ae

return handler.call(this, request, reply)

[Ekott2006]

So, what's next??

[airhorns]

@Ekott2006 @michele-tonizzo what did you want the onSend hook for for websockets? If you can describe your use case it would help us figure out if we need to go on the big adventure to add custom hooks to fastify proper or if there is a simpler way to accomplish what you are trying to do.

[michele-tonizzo]

@airhorns In my case I had to apply a mask to the reply after it was sent out of the route. For example users that can read other users shipping addresses but not their billing addresses. They had a permission mask user.userId=id1,id2.shipping

There surely are alternatives to solve my problem, for example I could do everything inside the route and get the users permissions and filter the data data = applyMask(data) before sending it back to the client reply.send(data) or I could select when reading the database.

But I wanted something that could be written inside a plugin in order to have a cleaner code (at the cost of speed, selecting when querying the db is much better move). The plugin would get the mask based on the user permissions and filter out the data automatically.

[airhorns]

@michele-tonizzo is the reply you were sending a websocket message or a normal JSON reply?

[michele-tonizzo]

It was a JSON serialised into a string and sent as websocket message

[airhorns]

Ah, ok. And I take it you were expecting the onSend hook to be called for each message sent out across the websocket?