how to guarantee my code execution completes?

sneakyimp

i have a complicated bit of PHP code that maintains a hierarchical data tree...it's a nested set / adjacency list hybrid.

there is only one person authorized to make changes to this data hierarchy and he uses pages that i have written to create/delete/move nodes in the tree.

in practice, he seems to be a bit impatient and sometimes tries to "cancel" or "refresh" prematurely while my php code is running which (and i'm not sure about this) seems to interrupt the sometimes lengthy code execution and leaves my database in a very awkward state.

IS THERE ANY WAY TO PREVENT MY CODE FROM BEING INTERRUPTED?

i have told him to be patient but i don't think he knows how serious it is if he interrupts the processing--and he expects to train other folks to use this when he moves to a different job.

any help would be much appreciated.

chads2k2

Hey what's up brother?

Yeah I have had that happen too. However, my best option was to have a shorter exectution of the scripts. That was what fixed my thing. I am sure you could get an average time of exectution and then just display a "Seconds till finished: $seconds" type thing going on. That way it's like a big count down till it will return control to the user.

Another thing is look at your code and see if you can cut things down and break your loops into smaller chuncks or watch the time it takes to exectute. I am not the best at optimization but I know there are some people on this board who are damn wizards at it! Just post the code (if possible) on here and see what they can do to make it execute faster. That is all the real advice I have. Also don't forget that there is a "disable" feature with form tags now. Such as <input type="submit" name="submitbutton" value="submit_now" disabled>

That will make the submit button not a real button. So when he clicks on submit you can have it disable the button. Which would be nice.

Hope everything works out for ya,

Chad

LordShryku

You could [man]ignore_user_abort[/man].
Output buffering is also an option. Display things to him at intervals like "I'm doing this right now. The script hasn't finished. Don't push refresh or I will sick a rabid dog on you".

sneakyimp

thanks guys!

shryku:
props! you never cease to amaze me. so before i start my code that shouldn't be interrupted, i do this:

ignore_user_abort(TRUE);

right? should i also set it to false after i'm complete or will the setting spill over into other pages visited during the session? i've read the docs and it doesn't seem to make it very clear.

chad:
my script is actually really short...no loops or anything. it's the database query that's a BEAST. i'm using nested set encoding so moving a tree branch requires that i update the LFT and RGT values of every node after the moving branch. if i move the first item in my data tree, the EVERY SINGLE NODE MUST BE UPDATED. it's therefore kinda slow sometimes. i'm considering some kind of hybrid adjency list / nested set approach (i.e., use adjacency list for edits, then update the LFT and RGT values of the whole tree before publishing, use nested set approach for performance for visitors) but i would have to incorporate all kinds of code to manage sequences for the adjacency list approach.

bottom line, i can't really speed my code up.

as for updating with "Seconds till finished: $seconds"...do you mean echoing and echoing every few seconds so you get

Seconds till finished: 10
Seconds till finished: 5
Seconds till finished:0
finishing...

that kind of thing?

as for the button disabling and so on...i'm pretty hip to that...it's useful for keeping users from clicking over and over again. i'm a bit wary of resorting to javascript because i've traditionally had problems making it work in every browser.

LordShryku

It's a single-script-only function, so on the script that does all of the work, just put it in there. It'll only be active for that script, and if he bails on it, it'll finish what it was doing anyway.

As for the javascript approach, making it work in all browsers isn't that hard, so long as you generalize. Like using

document.forms[0].submitButton.disabled = true;
# instead of
document.formName.submitButton.disabled = true;

Plus, you should have a good idea of what browsers you'll actually need to support, considering your limited user base for this page. But there's always the possibility of javascript being turned off in the browser, so it's a toss up.

Now knowing what you're doing in this script, I have to ask what kind of database it is. If it's MySQL, shame on you :p
If it's Oracle, Postgres or the like, then maybe the bulk of your database work could be put into a stored procedure. Then it would just be a matter of passing the variables to the procedure and being done with it. So instead of php having to wait for it to finish, you just call the proc. Just an idea...

sneakyimp

thanks again.

javascript tip WELL noted. yes, the audience is small and currently using the same platform/browser i am. should simplify things.

what's wrong with mysql??:glare:
yes i'm definitely using it. LOVE it.

LordShryku

MySQL doesn't have support for stored procedures. Like I explained below, that could have really simplified this whole thing. Plus, MySQL has a lot of other little qwerks that really erk me. To each his own though.

sneakyimp

thanks for the info.

yes i was previously aware of stored procedure limitation. i had previously worked on a geographic distance calculator and it would have been GREAT to have stored procedures so i could define a single fn get_great_circle_distance(long1, long2, lat1, lat2) instead of the BEASTLY query i ended up with.

thanks thanks thanks.