what's the fanws cookie?

I wrote a simple site using BedSheet to test adding cookies. When I ran the code and inspected the cookies using firebug, I found a extra cookie I didn't add named fanws (with value 06e3d816-7626-7b00-205a-0013e8a56e9d-dbc9c6c8fa03cfa4).

Here is my code:

class Site
{
    @Inject HttpCookies? cookie

    @Contribute { serviceType=Routes# }
    static Void contributeRoutes(Configuration Conf)
    {
        Conf.add(Route(`/index.html`, Site#index))
    }

    Text index()
    {
        cookie.add(Cookie("foo", "123"))
        return Text.fromHtml("<h1> Hello </h1>")
    }
}

What is this cookie? What is it used for? Where did this value come from?

fanws stands for Fanton Web Session and is added by the wisp web server to manage sessions. The value is just a UUID that uniquely identifies the session.

You can read more in the web pod's documentation on Web Sessions.