Extremely long wait time when loading REST resource from angularjs

Question

I'm building a front-end in angular that is accessing a flask/python RESTful API. I'm using AngularJS v1.2.16.

For some reason, it takes an insane amount of time before the REST resource is loaded, with most of the time just waiting. It's my understanding that 'waiting' is measuring the time to first byte - all my services run locally (the frontend, API and database).

Given that the services all run locally, I am at a loss how to debug this. Does anybody have any tips on where to look? I checked all my methods and they run decently fast (under 100ms per REST call). When I use postman, the API returns near-instantly.

Any ideas how to fix the wait, it only seems to be the case when loading the RESTful resource via angular. The angular $http get request is fairly straight forward:

myAppControllers.controller('ManageCtrl', ['$scope', '$http',
    function($scope, $http) {
        $http({
            url: 'http://127.0.0.1:5000/v1/domains/',
            method: "GET",
            headers: { 'Content-Type': 'application/json' },
        }).
        success(function(data, status, headers, config) {
            console.log('login successful');
            console.log(status);
            console.log(data);
        }).
        error(function(data, status, headers, config) {
            console.log('login failed');
        });
    }]);

EDIT:

• the issue only appears in Google Chrome, regular mode.
• the GET requests are fast when using incognito mode.

Answer 1

We had the same problem and after some research the problem is related with the way Chrome uses connections and the default configuration of flask as mono threaded.

Added threaded=true when flask app is started solved the problem:

app.run(threaded=True)

Answer 2

I've run into the same issue (Angular frontend running in Chrome and Flask backend). After trying both Angular 1.2.x and 1.3.x, and a billion other permutations, the only "solution" I've found is to run the Flask backend with the Tornado web server (http://www.tornadoweb.org/en/stable/). Other WSGI containers may work, but this is the one I tested.

In your Flask application, paste the following:

from tornado.wsgi import WSGIContainer
from tornado.httpserver import HTTPServer
from tornado.ioloop import IOLoop

if __name__ == '__main__':
  http_server = HTTPServer(WSGIContainer(app))
  http_server.listen(5000)
  IOLoop.instance().start()

You can start your web server by typing:

python myserver.py

Answer 3

I am facing now very similar issue. My current solution (acceptable for my chef at this moment :) ), which unfortunately not remove all problems, is to set header:{ 'Content-Type': 'application/json' } to { 'Content-Type': 'text/plain' }. Now only first GET request is crazy slow, any next takes less than 500ms. I am using Restangular on the frontend and wsgiref.simple_server on the backend.

Answer 4

I wanted to tie this in as well. But

app.run(threaded=True) 

worked for me!