Documentation > Administration > Web Services > WSGI Host Service

WSGI Host Service

Crossbar.io is able to host WSGI based Python applications, such as Flask, Pyramid or Django. This allows whole systems to be built and run from Crossbar.io, where classic Web parts are served from the former established Web frameworks, and running reactive parts of the application as WAMP components.

The WSGI Web application runs on a pool of worker threads, unmodified and as all WSGI applications in a synchronous, blocking mode. The WSGI application cannot directly interact with the WAMP router, due to the difference in synchronous versus asynchronous operation. However, full bidirectional WAMP integration can be achieved using the HTTP Bridge.

Configuration

To configure a WSGI Web service, attach a dictionary element to a path in your Web transport:

attribute description
type Must be "wsgi".
module The WSGI app Python module to load.
object The WSGI app Python object to use.

Example

See here for a complete example.

Here is a minimal example using Flask. The overall files involved are:

myapp.py
templates/index.html
.crossbar/config.json

Create a file myapp.py with your Flask application object:

from flask import Flask, render_template

##
## Our WSGI application .. in this case Flask based
##
app = Flask(__name__)


@app.route('/')
def page_home():
   return render_template('index.html', message = "Hello from Crossbar.io")

Create a Jinja template file templates/index.html (note the templates subfolder):

<!DOCTYPE html>
<html>
   <body>
      <h1>{{ message }}</h1>
   </body>
</html>

Add a Web Transport with a WSGI Host Service on a subpath within your node configuration:

{
   "controller": {
   },
   "workers": [
      {
         "type": "router",
         "options": {
            "pythonpath": [".."]
         },
         "transports": [
            {
               "type": "web",
               "endpoint": {
                  "type": "tcp",
                  "port": 8080
               },
               "paths": {
                  "/": {
                     "type": "wsgi",
                     "module": "myapp",
                     "object": "app"
                  },
                  "ws": {
                     "type": "websocket"
                  }
               }
            }
         ]
      }
   ]
}
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