Python access to web directory

[tim.in...@gmail.com]

Hi Tobias,

I am evaluating Crossbar.io for an access control system, to be able to grab information from the database and serve it
across a local network to a web browser. For example, when a user scans their card at the reader,
their user-name and photo are published (pubsub) together with the door name and time. Elsewhere in the building, perhaps
at the security desk, this information is displayed in a web browser. Crossbar.io looks awesome for this because
the transport is all taken care of and we can take advantage of the advanced formatting capabilities in modern web browsers
to display the information however we like and so easily. This looks incredibly powerful.

Using one of the hello demos as a starting point, the Crossbar.io configuration supports a web server to deliver
the static web pages, and pubsub so the user details can be dynamically pushed across to the remote web browser.
This is all working great so far. I can display the user-name, door and time on the remote web page. Now I am up against my next hurdle, I need
to pass the photo across or, rather, the pathname to the photo. The photos referenced by the access control system's database
are not in the same directory as the static web pages, so I will translate the photo absolute pathname into a path
relative to the web root, but how do I get the web root from crossbar.io (or autobahn) within Python ?

Regards,
Tim

[Tobias Oberstein]

Tim,

Prenote: I am cross-posting to Autobahn list since (due to historic
reasons), a lot of Crossbar.io related discussion is still there ..

Am 14.08.2014 15:40, schrieb tim.in...@gmail.com:
> Hi Tobias,
>
> I am evaluating Crossbar.io for an access control system, to be able to
> grab information from the database and serve it
> across a local network to a web browser. For example, when a user scans
> their card at the reader,
> their user-name and photo are published (pubsub) together with the door
> name and time. Elsewhere in the building, perhaps
> at the security desk, this information is displayed in a web browser.

Neat! That's an interesting application ..

> Crossbar.io looks awesome for this because
> the transport is all taken care of and we can take advantage of the
> advanced formatting capabilities in modern web browsers
> to display the information however we like and so easily. This looks
> incredibly powerful.

Oh yeah, the modern browser is probably now _the_ most capable frontend
run-time available. Plus: no vendor lock in etc.

>
> Using one of the hello demos as a starting point, the Crossbar.io
> configuration supports a web server to deliver
> the static web pages, and pubsub so the user details can be dynamically
> pushed across to the remote web browser.

Yes.

> This is all working great so far. I can display the user-name, door and
> time on the remote web page. Now I am up against my next hurdle, I need
> to pass the photo across or, rather, the pathname to the photo. The
> photos referenced by the access control system's database
> are not in the same directory as the static web pages, so I will
> translate the photo absolute pathname into a path
> relative to the web root, but how do I get the web root from crossbar.io
> (or autobahn) within Python ?

Python application components run by Crossbar.io don't have (direct)
access to the configuration part for static Web serving. This is by design.

However, you can forward _arbitrary_ info from the config to your component.

Here is how:

"components": [
{
"type": "class",
"classname": "votes.VotesBackend",
"realm": "realm1",
"role": "anonymous",
"extra": {
"foo": "bar"
}
}
]

The "extra" can be anything you like.

You then access this "extra" stuff like this:

class VotesBackend(ApplicationSession):

def __init__(self, config):
print("Component extra config: {}".format(config.extra))
ApplicationSession.__init__(self, config)

Which means, you can forward the path to the picture directory without
hard-coding into your app component.

===

Curious: how do you upload pictures to that directory? Since Crossbar.io
has a static Web server .. but (currently) does not support
HTTP/POST/PUTting stuff up.

Technically, adding such a capability to Crossbar.io builtin Web server
would be trivial.

The other question is: we need to find a "cutoff" what's builtin. It
must be generic, and it must be applicable in broader situations.

If you have ideas, feel free to start a discussion or even file an issue
and leave your thoughts there.

Anyway, please let me know if above "extra" config stuff solves your
immediate problem at hand ..

Cheers,
/Tobias



>
> Regards,
> Tim
>
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[tim.in...@gmail.com]

Tobias,

Thanks for the info to forward extra stuff from the config file. That works
perfectly.

>>Curious: how do you upload pictures to that directory? Since Crossbar.io
>>has a static Web server .. but (currently) does not support
>>HTTP/POST/PUTting stuff up.

In the Python code I copy the image file into a sub-directory of the web root and
then pubsub the copied pathname. Its not as clean as I would like but it seems
a reasonable compromise given the images can be stored anywhere on the local network
and they can be kept to reasonable file sizes.

Cheers,
Tim