How to reply from outside of the hapi.js route handler

Question

I have a hapi.js route where I want to defer the response. I've tried storing the reply function and calling it later, or wrapping it in a promise, but hapi always responds immediately with a 500 Internal Server Error response.

Store the reply for later:

var pendingReplies = {};
server.route({
    method: "POST",
    path: "/",
    handler: function (request, reply) {
        var id = generateId();
        pendingReplies[id] = reply;
    }
});
... // reply later by calling:
function sendResponse(id, data) {
    pendingReplies[id](data);
}

I've tried creating a promise to reply:

handler: function (request, reply) {
    var id = generateId();
    return new Promise(function (resolve, reject) {
        pendingReplies[id] = resolve;
    }).then(function (data) {
        return reply(data);
    });
}

I've tried using reply().hold()

handler: function (request, reply) {
    var id = generateId();
    var response = reply().hold();
    pendingReplies[id] = function (data) {
        response.source = data;
        response.send();
    };
    return response;
}

I've tried using reply().hold() with a Promise:

handler: function (request, reply) {
    var id = generateId();
    var response = reply().hold();
    return new Promise(function (resolve, reject) {
        pendingReplies[id] = resolve;
    }).then(function (data) {
        response.source = data;
        response.send();
        return response;
    });
}

With each of these, as soon as the handler function exits, I get a 500 response and the following output in the node console:

Debug: internal, implementation, error
    Error: Uncaught error: socket hang up
    at createHangUpError (_http_client.js:198:15)
    at Socket.socketOnEnd (_http_client.js:283:23)
    at emitNone (events.js:72:20)
    at Socket.emit (events.js:163:7)
    at _stream_readable.js:891:16
    at process._tickDomainCallback (node.js:388:13)

Is it possible with hapi to reply to a request asynchronously from outside of the route handler?

Answer 1

If an error is thrown within your handler, hapi.js will immediately exit and give a 500 status code. Check if generateId() is a valid function.

The rest of your code looks right for your third and fourth examples. reply().hold() is necessary to keep the connection open after handler returns.

Answer 2

Since the version 8, Hapi supports Promised responses, so you can do :

var respond = function(message) {
    return new Bluebird.Promise(function(resolve, reject) {
        setTimeout(() => {
            resolve(message);
        }, 2000);
    });
};

server.route({
    method: 'GET',
    path: '/',
    handler: function (request, reply) {
        reply(respond("Hello buddy"));
    }
});