I did not know #'app is for reload. It's very helpful. Thanks.
On Saturday, January 19, 2013 5:26:06 PM UTC+8, Baishampayan Ghose wrote:
>
> On Sat, Jan 19, 2013 at 5:24 AM, faenvie <fanny....@gmx.de <javascript:>>
> wrote:
> > i have learned that for a ring/compojure-app the embedded jetty
> > service can be started like this:
> >
> > (def app (handler/site routes))
> >
> > (defn start [port]
> > (ring/run-jetty (var app) {:port (or port 8080)
> > :join? false}))
> >
> > can anyone explain, what is the var for ? why '(var app)' or #'app ?
> > i found some remarks about being able to change the app without
> > having to restart the server but how exactly does this relate ?
>
> If you pass in the app as it is, then the var gets evaluated to the
> function that the var refers to and the jetty adapter uses that
> function to run the server.
>
> Now if you recompile your ring handlers (aka functions) the same app
> var will get rebound to a new function while the jetty server will
> continue holding on to the old handler function, so if you refresh the
> page, etc. you won't see the change on your browser. You will have to
> kill the server and restart jetty.
>
> If you pass just the var instead, jetty holds on to the container (the
> var) and not the value. The jetty-adapter derefs the var on every
> request and sends the response back. As a result if you recompile your
> handlers you'll see the effects immediately without restarting the
> server.
>
> The derefing has a penalty, albeit minor. Thus, you may choose to not
> pass in the app as a var in production deployments.
>
> Regards,
> BG
>
>
>
> --
> Baishampayan Ghose
> b.ghose at gmail.com
>
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