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Posted to modperl@perl.apache.org by Worik Stanton <wo...@gmail.com> on 2014/05/19 00:39:59 UTC
Trouble with script execution
I am having a nproblem executing my handler.
The short of it is it is when I make a change to the script I have to
restart the server to get it noticed, and it does not always call the
same code.
The lng of it:
I have a package with a 'handler' function.
It starts...
package Apache::Script;
use strict;
use Apache2::Const qw(:common);
use Apache2::Connection;
[snip]
sub handler {
warn "Apache::Script::handler $$ '".join(", ", @_)."'";
my $r = shift;
[snip]
Many more lines like...
warn "Apache::Script::handler";
And in the config file:
<Location /Script>
SetHandler perl-script
PerlResponseHandler Apache::Script
</Location>
Repeatedly loading the URL I get different results almost every time.
With the first 'warn' statement producing oyutput almst every iteration
and occasionally the later warn statements not being executed, and often
with no output.
Making changes t the script (adding debugging 'warn' statements) are
only reliably (ish) noticed if I restart the server. There is some
unreliability in my code (bugs) I am trying to track down but it is
confounded by the fact I am not sure what mod_perl is doing.
There seems to be a time element. After restarting the server
everything goes well for a while (minutes) but soon behaviour changes
and I am back to only some of the code executing (with no oither changes
but the passing of time).
I thought mod_perl would reload code that changed. Is this wrong?
Worik
--
The only true evil is turning people into things....
Granny Weatherwax
worik.stanton@gmail.com 021-1680650, (03) 4821804
Aotearoa (New Zealand)
Re: Trouble with script execution
Posted by Perrin Harkins <ph...@gmail.com>.
On Sun, May 18, 2014 at 9:47 PM, Worik Stanton <wo...@gmail.com> wrote:
> I am sure I read somewhere that mod_perl monitors scripts and reloads
> them if the modification date changes.
You're probably thinking of Apache::Registry/ModPerl::Registry. They
do that with your CGI scripts.
- Perrin
Re: Trouble with script execution
Posted by John Dunlap <jo...@lariat.co>.
That hasn't been my experience. I always need to restart the server. One of
the challenges with that is that objects can persist in memory between
requests because the perl runtime persists between requests. If the
"script" changes, how do you apply those changes to objects instances which
already exist in memory? It is not a simple problem and it exists in other
languages(java) as well. Entire companies(ZeroTurnaround) have been built
around solving this kind of problem. The only reason that you can make
changes in a language like php without a server restart is because php
objects cannot persist between requests like they can in perl or Java and
that approach has its own disadvantages.
On May 18, 2014 9:47 PM, "Worik Stanton" <wo...@gmail.com> wrote:
> On 19/05/14 12:13, Brad Van Sickle wrote:
> > Yep you need to restart to see your changes.
>
> I am sure I read somewhere that mod_perl monitors scripts and reloads
> them if the modification date changes. But oh well. It definitely
> notices sometimes.
>
> cheers
> Worik
>
> --
> The only true evil is turning people into things....
> Granny Weatherwax
> worik.stanton@gmail.com 021-1680650, (03) 4821804
> Aotearoa (New Zealand)
>
>
Re: Trouble with script execution
Posted by Jie Gao <J....@sydney.edu.au>.
Apache2::Reload
Regards,
Jie
* Worik Stanton <wo...@gmail.com> wrote:
> Date: Mon, 19 May 2014 13:47:12 +1200
> From: Worik Stanton <wo...@gmail.com>
> CC: mod_perl list <mo...@perl.apache.org>
> Subject: Re: Trouble with script execution
> User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101
> Thunderbird/24.5.0
>
> On 19/05/14 12:13, Brad Van Sickle wrote:
> > Yep you need to restart to see your changes.
>
> I am sure I read somewhere that mod_perl monitors scripts and reloads
> them if the modification date changes. But oh well. It definitely
> notices sometimes.
>
> cheers
> Worik
>
> --
> The only true evil is turning people into things....
> Granny Weatherwax
> worik.stanton@gmail.com 021-1680650, (03) 4821804
> Aotearoa (New Zealand)
>
Re: Trouble with script execution
Posted by Worik Stanton <wo...@gmail.com>.
On 19/05/14 12:13, Brad Van Sickle wrote:
> Yep you need to restart to see your changes.
I am sure I read somewhere that mod_perl monitors scripts and reloads
them if the modification date changes. But oh well. It definitely
notices sometimes.
cheers
Worik
--
The only true evil is turning people into things....
Granny Weatherwax
worik.stanton@gmail.com 021-1680650, (03) 4821804
Aotearoa (New Zealand)
Re: Trouble with script execution
Posted by Brad Van Sickle <bv...@gmail.com>.
Yep you need to restart to see your changes.
Believe it or not, that's one of the *nice* things about mod_perl.
Instead of compiling the code during each execution as PERL does when
executed as a purely interpreted language , mod_perl causes each Apache
child process to compile the code during it's first request/execution
and then caches that compiled version of that code. You will need to
restart the web server to clear that cache and force your changes to
take effect.
This is probably why you're getting inconsistent results after code
changes, your seeing some requests that are handled by "new" child
processes that are compiling the latest version of your code and some
requests that are being handled by "old" child processes which are still
serving previous versions that they've complied and cached.
It may seem inconvenient for you, but this type of caching is a
*necessity* when running PERL on any sort of "real" website that gets an
appreciable amount of traffic for performance reasons.
There are methods you can employ that tell Apache to automatically
reload when it sees code change, pretty easy to find if you dig around
the Internet. Although I wouldn't use this in a production system.
On 5/18/2014 8:04 PM, Worik Stanton wrote:
> On 19/05/14 11:34, John Dunlap wrote:
>> No, you have to restart the server for code changes to be noticed.
> Does that mean I have to restart my server for every change to a script?
>
> Worik
>
Re: Trouble with script execution
Posted by Worik Stanton <wo...@gmail.com>.
On 19/05/14 11:34, John Dunlap wrote:
> No, you have to restart the server for code changes to be noticed.
Does that mean I have to restart my server for every change to a script?
Worik
--
The only true evil is turning people into things....
Granny Weatherwax
worik.stanton@gmail.com 021-1680650, (03) 4821804
Aotearoa (New Zealand)
Re: Trouble with script execution
Posted by John Dunlap <jo...@lariat.co>.
No, you have to restart the server for code changes to be noticed.
On May 18, 2014 6:48 PM, "Worik Stanton" <wo...@gmail.com> wrote:
> I am having a nproblem executing my handler.
>
> The short of it is it is when I make a change to the script I have to
> restart the server to get it noticed, and it does not always call the
> same code.
>
> The lng of it:
>
> I have a package with a 'handler' function.
>
> It starts...
>
> package Apache::Script;
> use strict;
> use Apache2::Const qw(:common);
> use Apache2::Connection;
> [snip]
> sub handler {
> warn "Apache::Script::handler $$ '".join(", ", @_)."'";
> my $r = shift;
> [snip]
> Many more lines like...
> warn "Apache::Script::handler";
>
> And in the config file:
> <Location /Script>
> SetHandler perl-script
> PerlResponseHandler Apache::Script
> </Location>
>
>
> Repeatedly loading the URL I get different results almost every time.
> With the first 'warn' statement producing oyutput almst every iteration
> and occasionally the later warn statements not being executed, and often
> with no output.
>
> Making changes t the script (adding debugging 'warn' statements) are
> only reliably (ish) noticed if I restart the server. There is some
> unreliability in my code (bugs) I am trying to track down but it is
> confounded by the fact I am not sure what mod_perl is doing.
>
> There seems to be a time element. After restarting the server
> everything goes well for a while (minutes) but soon behaviour changes
> and I am back to only some of the code executing (with no oither changes
> but the passing of time).
>
> I thought mod_perl would reload code that changed. Is this wrong?
>
> Worik
> --
> The only true evil is turning people into things....
> Granny Weatherwax
> worik.stanton@gmail.com 021-1680650, (03) 4821804
> Aotearoa (New Zealand)
>
>