Restify.js (Connect/Express) middleware ignoring call to next() within promise callback

Question

So. I'm experiencing some quirks when attempting to implement some basic middleware for a Restify.js application I'm building with specific regard to next() and promise callbacks.

To express the problem in a generic form:

  var server = restify.createServer({
    name: config.name
  });

Promise resolves:

  server.use(function checkAcl(req, res, next) {
    // Promise is resolved
    var promise = function () {
      var deferred = require('q').defer();
      deferred.resolve();
      return deferred.promise;
    }

    promise()
      .then(function () {
        next(); // doesn't get 'called', no response sent, connection eventually times out
      }, function () {
        res.send(new restify.NotAuthorizedError());
      });
  });
  server.use(restify.bodyParser());

  ...

Promise is rejected

  server.use(function checkAcl(req, res, next) {
    // Promise is rejected
    var promise = function () {
      var deferred = require('q').defer();
      deferred.reject();
      return deferred.promise;
    }

    promise()
      .then(function () {
        next(); 
      }, function () {
        res.send(new restify.NotAuthorizedError()); // this works fine
      });
    }
  });

  server.use(restify.bodyParser());      

  ...

Am I doing anything obviously wrong? Any insight? It certainly seems to been related to the promise callbacks, are they somehow suppressing the call to next()?

ok, so in the example above. ACL passes `(allowed === true)` so to answer your question directly: AuthToken Verified, Found User, ACL Passed — Matt Richards, Jun 13 '13 at 16:18
updated the question with a more generic representation of the problem (see bottom). — Matt Richards, Jun 13 '13 at 16:28
what if you replace the promise code with `setTimeout(function () { next(); }, 0);`? Also try just calling `next()` directly. — Domenic, Jun 13 '13 at 17:12
BTW you can replace those lines with `var promise = Q.resolve()` and `var promise = Q.reject()` then replace `promise()` with `promise`. — Domenic, Jun 13 '13 at 17:12
The problem seems related to my use of ` server.use(restify.bodyParser());` (which I had neglected to mention). Changing the order of the `server.use()` declarations seems to have solved the problem. — Matt Richards, Jun 13 '13 at 17:18

Matt Richards · Accepted Answer · 2013-06-13T18:30:37.873

Adding the restify.bodyParser() middleware BEFORE the custom middleware resolves the issue.

n.b:

  // Add bodyParser() to the stack before the custom middleware
  server.use(restify.bodyParser()); 

  server.use(function checkAcl(req, res, next) {
    // Promise is resolved
    var promise = function () {
      var deferred = require('q').defer();
      deferred.resolve();
      return deferred.promise;
    }

    promise()
      .then(function () {
        next(); // next() now behaves as expected.
      }, function () {
        res.send(new restify.NotAuthorizedError());
      });
  });
  ...

Further to that, I eventually happened upon this Github issue describing the issue along with another possible solution if the order of your middleware matters (which it probably does).

mcavage: Pretty sure this is actually node that's biting you (as in your data is emitted to nowhere). Try this:

  var server.createServer();
  server.pre(restify.pre.pause());
  ...

Restify.js (Connect/Express) middleware ignoring call to next() within promise callback

1 Answers1