The Web Console

Circus comes with a Web Console that can be used to manage the system.

The Web Console lets you:

  • Connect to any running Circus system
  • Watch the processes CPU and Memory usage in real-time
  • Add or kill processes
  • Add new watchers


The real-time CPU & Memory usage feature uses the stats socket. If you want to activate it, make sure the Circus system you’ll connect to has the stats enpoint enabled in its configuration:

stats_endpoint = tcp://

By default, this option is not activated.

The web console needs a few dependencies that you can install them using the web-requirements.txt file. Additionally, you will need to have gevent (and thus libevent) installed on your system to make this working:

$ bin/pip install -r web-requirements.txt

To enable the console, add a few options in the Circus ini file:

httpd = True
httpd_host = localhost
httpd_port = 8080

httpd_host and httpd_port are optional, and default to localhost and 8080.

If you want to run the web app on its own, just run the circushttpd script:

$ circushttpd
Bottle server starting up...
Listening on http://localhost:8080/
Hit Ctrl-C to quit.

By default the script will run the Web Console on port 8080, but the –port option can be used to change it.

Using the console

Once the script is running, you can open a browser and visit http://localhost:8080. You should get this screen:


The Web Console is ready to be connected to a Circus system, given its endpoint. By default the endpoint is tcp://

Once you hit Connect, the web application will connect to the Circus system.

With the Web Console logged in, you should get a list of watchers, and a real-time status of the two Circus processes (circusd and circusd-stats).


You can click on the status of each watcher to toggle it from Active (green) to Inactive (red). This change is effective immediatly and let you start & stop watchers.

If you click on the watcher name, you will get a web page for that particular watcher, with its processes:


On this screen, you can add or remove processes, and kill existing ones.

Last but not least, you can add a brand new watcher by clicking on the Add Watcher link in the left menu:


Embedding circushttpd into Circus

circushttpd is a WSGI application so you can run it with any web server that’s compatible with that protocol. By default it uses the standard library wsgiref server, but that server does not really support any load.

You can use Chaussette to bind a WSGI server and have circushttpd managed by Circus itself.

To do so, make sure Chaussette is installed:

$ pip install chaussette

Then add a new watcher and a socket sections in your ini file:

cmd = chaussette --fd $(circus.sockets.webconsole)
singleton = 1
use_sockets = 1

host =
port = 8080

That’s it !

Running behind Nginx and Varnish

Nginx can act as a proxy in front of Circus. It an also deal with security.

To hook Nginx, you define a location directive that proxies the calls to Circus.


location ~/media/*(.jpg|.css|.js)$ {
    alias /path/to/circus/web/;

location / {
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    proxy_set_header Host $http_host;
    proxy_redirect off;

If you want more configuration options, see

Websockets in Nginx (v1.2.5) is currently unsupported, although it will be implemented in 1.3. To receive real-time statuses and graphs in the web console, you need to use a websocket-compatible proxy like Varnish or HAProxy. In Varnish, two backends can be defined: one for serving the web console and one for the handling the socket connections.


backend default {
    .host = "";
    .port = "8001";

backend socket {
    .host = "";
    .port = "8080";
    .connect_timeout = 1s;
    .first_byte_timeout = 2s;
    .between_bytes_timeout = 60s;

sub vcl_pipe {
     if (req.http.upgrade) {
         set bereq.http.upgrade = req.http.upgrade;

sub vcl_recv {
    if (req.http.Upgrade ~ "(?i)websocket") {
        set req.backend = socket;
      return (pipe);

Here, web console requests are bound to port 8001, and Nginx should be configured to listen on that port. Websocket connections are upgraded and piped directly to the circushttpd process listening on port 8080.

Password-protect circushttpd

As explained in the Security page, running circushttpd is pretty unsafe. We don’t provide any security in Circus itself, but you can protect your console at the NGinx level, by using


location / {
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    proxy_set_header Host $http_host;
    proxy_redirect off;
    auth_basic            "Restricted";
    auth_basic_user_file  /path/to/htpasswd;

The htpasswd file contains users and their passwords, and a password prompt will pop when you access the console.

You can use Apache’s htpasswd script to edit it, or the Python script they provide at:

Of course that’s just one way to protect your web console, you could use many other techniques.

Extending the web console

We picked bottle to build the webconsole, mainly because it’s a really tiny framework that doesn’t do much. By having a look at the code of the web console, you’ll eventually find out that it’s really simple to understand.

Here is how it’s split:

  • The file contains the “views” definitions and some code to handle the socket connection (via socketio).
  • the contains a single class which is in charge of doing the communication with the circus controller. It allows to have a nicer high level API when defining the web server.

If you want to add a feature in the web console you can reuse the code that’s existing. A few tools are at your disposal to ease the process:

  • There is a render_template function, which takes the named arguments you pass to it and pass them to the template renderer and return the resulting HTML. It also passes some additional variables, such as the session, the circus version and the client if defined.
  • If you want to run commands and doa redirection depending the result of it, you can use the run_command function, which takes a callable as a first argument, a message in case of success and a redirection url.

The StatsNamespace class is responsible for managing the websocket communication on the server side. Its documentation should help you to understand what it does.