Re: [Gambas-user] A couple of questions about building web / cgi applications

[Caveat <Ga...@ca...>]

If you're going to use a database to communicate between 2 separate 
programs, be sure to set the transaction isolation to READ-COMITTED 
(good for MySQL, ymmv), otherwise you won't see updates made by another 
process which can lead to some frustrating and confusing mismatches 
between what you think should be read from the database and what 
actually gets read!

You may also want to look at in-memory databases, if you don't need the 
sensor data to be persistent.  H2: 
http://www.h2database.com/html/main.html and JavaDB: 
http://docs.oracle.com/javadb/10.8.3.0/getstart/index.html
might be worth a look.  You could always use a regular database for the 
less volatile data, like user settings etc. and I imagine the 
inter-process communication would be easier to set up using a normal 
disk-based database.

The architecture is sound, I use a raspberry pi in a similar way to 
control my central heating.  There's a python script running all the 
time checking for interrupts so you can hit a button on the pi (PiFace 
board added) to, for example, force the heating on.  The python script 
reads from the MySQL db to see what temperature it should be aiming for, 
and reads a usb thermometer to see what the temperature actually is.  
There's a web interface written in php with big friendly buttons to 
force the heating on or off, and a nice display of the current 
temperature and the target temperature, and an indication of the state 
of the heating (on or off).  Inter-process communication is all done via 
the heating database in MySQL (with tx-isolation as above!).

Sorry, kind of realised at the end this is a little off-topic for most 
of the Gambas list, what if I promise to rewrite my web-interface in 
Gambas CGI? :-)

Kind regards,
Caveat


On 13/02/15 09:42, Rolf-Werner Eilert wrote:
>
>
> Am 12.02.2015 19:09, schrieb Bruce Cunningham:
>> I'm looking for some advice and maybe some code examples for a 
>> project I'm starting.  I'm building an embedded device with an ARM 
>> based System-On-Module (similar to an Rpi, but in an sodimm form 
>> factor).
>>
>> Thanks to some great help from members of this mailing list, I have 
>> successfully compiled Gambas for the SOM.  The device will have a 
>> "main" GUI application that handles the user interface and all of the 
>> control logic.  However, it will also have a web interface for remote 
>> access to some of the control settings.
>>
>> Here are my questions:
>>
>> 1) Does anyone have any code examples for CGI applications in 
>> Gambas?  I know there is an option to use the Gambas interpreter to 
>> build ASP-like pages, but I would rather the web code be in compiled 
>> into a CGI module instead (for security reasons).  I've built CGI 
>> applications in VB6, so I have a fairly good understanding how CGI 
>> work in general.  I've read the Gambas docs on CGI, but I still don't 
>> quite understand it.
>>
>> 2) What is the easiest way to exchange data (variables and arrays) 
>> between the CGI module, and the main application?  Using a file on 
>> disk is not a great option, since the device will be using flash for 
>> the file system, and these values will be changing several times a 
>> second.  That will kill the flash very quickly.
>>
>> Thanks,
>>
>> Bruce Cunningham
>> bcu...@sp...<mailto:bcu...@sp...>
>
> Hi Bruce,
>
> although I see your point, I don't see where there is a difference 
> between a gb.web app and an all-in-one app (apart from the ASP-like 
> pages to be stored separately). BUT: I once made some projects this 
> way, back in the times of Gambas2, so here is what I have (comments 
> are in German, and scarce, so if you have any questions...)
>
> One of the projects (umfragen) is still publicly running on our 
> website at 
> http://www.eilert-sprachen.de/cgi-bin/Umfragen.gambas?Selbsttest.data
>
> Take a look at those SUBs which start with "schreibe" (write), that's 
> the core of it.
>
> Hope it helps!
>
> Regards
> Rolf
>
>
>
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