How to make Server Vars persistant.

[ColinJD]

I have an application where the best arrangement and scope of variables is as server variables. {not application or session}
The drawback is that everytime the server is restarted, the server variables are removed.
I am considering making any change to the server variables to be stored in a registry field.
But .... What event is fired whence the server is started.
An event must be started as the 3 logs all indicate they recieve notification.
Any hints appreciated.
(I realise the other method is to test for existance when required of the variables however this seems ugly to me.)

[Pat Bremkamp]

Re: How to make Server Vars persistant.

This may be "ugly", but I created a table named "version" and a page named ServerVarTest.a5w as follows:

 
<%a5
'==== get section info into server variables if needed
If eval_valid("server.number")=.f.
 stbl=table.open("[PathAlias.ADB_Path]\version")
 stbl.fetch_goto(1)
 server.version = alltrim(stbl.Ver_no)
 server.number = alltrim(stbl.En_id)
 server.name = alltrim(stbl.En_name)
 server.address = alltrim(stbl.En_adr1)
 server.citystzip = alltrim(stbl.En_city)+", "+alltrim(stbl.En_state)+" "+alltrim(stbl.En_zip)+"-"+stbl.En_zip4
 server.logoname = alltrim(stbl.Logoname)
 server.logohigh = alltrim(stbl.Logohigh)
 server.logowide = alltrim(stbl.Logowide)
 server.logoalt = alltrim(stbl.Logoalt)
 server.copyright = alltrim(stbl.En_footer1)
 server.footer1 = alltrim(stbl.En_footer2)
 server.footer2 = alltrim(stbl.En_footer3)
 server.website = alltrim(stbl.En_website)
 stbl.close()
end if
%>

Then at the top of each page, I just

 
a5w_include("ServerVarTest.a5w")

Pat

[ColinJD]

Re: How to make Server Vars persistant.

Pat , that is exactly the same, apart form tbl an var names, to what I have been using.
I just keep thinking there must be a better way than using the eval_valid("
type test.

[Steve Wood]

Re: How to make Server Vars persistant.

What's wrong with using eval_valid()? It just says if that variable is missing, to reset all from the table, else assume they are all set.

[ColinJD]

Re: How to make Server Vars persistant.

Steve, Ill give you, Eval_Valid functions and is reliable.
However I wonder how it will perform as a function in a multi threaded environment, where I believe most of us are heading. I consider it to be a function to be used for safety testing rather than falling back on error_handling routines. Thus using it as as a standard code requirement (similar to the file-upload situation on here yesterday) just doesn't seem right to me. Similar other evaluation type functions in XBAsic I avoid if possible.

[Steve Wood]

Re: How to make Server Vars persistant.

I've never heard anyone else mention multi-threaded regarding Alpha web apps, so I think your out front. Eval_valid() just checks if the expression is valid, don't know how that would be affected by multiple threads. Each thread would need the same check I guess.

If it helps, here is an old video on how to "Make an Autoexec for your Alpha Application Server". It uses AlwaysUP and CURL. The example sets the CPU and sends an email saying the server restarted.

http://www.alphatogo.com/openfile.a5...48BFA1CC3FF170

[ColinJD]

Re: How to make Server Vars persistant.

Make an Autoexec for your Alpha Application Server".

Ah, That was the kick in the pants I needed, I should have thought of an AutoExec First !
-
Note: Threading
I running into aprox one new threading issue a fortnight, principally thanks to AJAX callbacks, I have been surprised at how few others on this board are reporting issues with it. I'm unsure how the new V10 grid will handle this. Currently the Application Server appears to only handle one thread per session, However bogus_sessions allow for extra threads.

[Steve Wood]

Re: How to make Server Vars persistant.

Can you expand on how threading will or may affect the AJAX grids. I mean if we are not specifically creating multi-threaded applications, is this a potential problem? Or do you mean by nature, the AJAX callbacks and grid ARE making our apps multi threaded just by their use?

[ColinJD]

Re: How to make Server Vars persistant.

Will try to explain, (if I don't overly confuse myself) :-)
My situation is that I am using and probably overusing AJAX functions and call backs, with my maps etc.
-
Ok, a webpage
May fire two functions
1.)
a5_AJAX_Callback('www.server1.com/AZMAP.AJAX.A5W','action=action1_.....
which returns ?"alert('Return First');"
and then ?"alert('Return Second');"

next 2.)
a5_AJAX_Callback('www.server2.com/GMAP.AJAX.A5W','action=action1_.....
which returns ?"alert('Return Third');"
and then ?"alert('Return Fourth');"

Ok here we have no guarantee that the REturned callbacks will be in the order
Return First, Return Second, Return Third, Return Fourth
-
This is because A. the servers are different for the two AJAX functions,
Also with internet slowness issues a problem can exist.
-
Obviously the example above gets more complicated and can return more unexpected results.
-

Thus I'm learning now to write code that is more robust,
In the simple form,
i.)
Only fire 1 callback function at a time, then to queue subsequent functions until the last result has been returned. if the wait is too long fire another callback.
ii.) on the AJAX.a5w pages, to only return the functions etc as one statement back to the client page.

Another problem is different browsers handle callback timing differently eg event bubbling and event boiling. So a quick fix may work on one setup but not another
-
If Alpha have designed the V10 grid well I doubt this will be an issue, however if a developer decides to intergrate a 3rd party json type feed into a grid there may well be conflicts. Remembering Xbasic is essentially synchronous whilst javascipt and AJAX are Asynchronous with one or two exceptions.

[Steve Wood]

Re: How to make Server Vars persistant.

event bubbling and event boiling

Any Event Gurgling? Your description did make perfect sense and I see how AJAX adds the potential for multiple threads. The above metaphor works (multiple events from a single source) except it misses that the events may be dependent on each other.

As a comparison, I know when I use Xbasic to ask for a response from another web page, it waits until the response is received before continuing. Even if the response is never received, the function has to be set to time out, or the browser times out on its own. Only then does it continue with the rest of the script. The other perfect example is when a web page script sends an email and the browser 'hangs' while it sends the email*. That's single threaded. If it were multi-threaded, the instruction to send the email would go on a new thread and the browser would respond instantly - and the email would be sent out on a different thread.

I see how this changes things since, as a developer, I currently rely on that single threaded timing.

*I never send an email as part of a Grid event because of this.