[32247] in Perl-Users-Digest
Perl-Users Digest, Issue: 3514 Volume: 11
daemon@ATHENA.MIT.EDU (Perl-Users Digest)
Sat Oct 8 03:09:24 2011
Date: Sat, 8 Oct 2011 00:09:06 -0700 (PDT)
From: Perl-Users Digest <Perl-Users-Request@ruby.OCE.ORST.EDU>
To: Perl-Users@ruby.OCE.ORST.EDU (Perl-Users Digest)
Perl-Users Digest Sat, 8 Oct 2011 Volume: 11 Number: 3514
Today's topics:
Help me to Improve <sssdevelop@gmail.com>
Re: Help me to Improve <tadmc@seesig.invalid>
Re: Help me to Improve <tadmc@seesig.invalid>
Re: Help me to Improve <ben@morrow.me.uk>
Re: Help me to Improve <sssdevelop@gmail.com>
how to start perl on android tablet? <marko.toplica.makni.ovo.@gmail.com>
Re: how to start perl on android tablet? <kkeller-usenet@wombat.san-francisco.ca.us>
Posting Guidelines for comp.lang.perl.misc ($Revision: tadmc@seesig.invalid
Digest Administrivia (Last modified: 6 Apr 01) (Perl-Users-Digest Admin)
----------------------------------------------------------------------
Date: Fri, 7 Oct 2011 06:33:14 -0700 (PDT)
From: SSS Develop <sssdevelop@gmail.com>
Subject: Help me to Improve
Message-Id: <60e8b9dd-afc8-4e3b-8f0a-767e47f22b50@g23g2000vbz.googlegroups.com>
Hello,
The intention to ask question in this forum is to improve this piece
of code (for performance and other best practices)
I have couple of Web Applications - need to monitor the HTTP Response
for them. Decided to use the Perl - the script should fetch the HTTP
page from Web App within SLA time (Service Level). If the SLA did not
met - then system should send alert. For sending alert, it interacts
with command line tools like email/nagios.
SLA's are in seconds.
Typical file structure of application is as follow:
/bin/httpresp.pl
/conf/{app1.conf, app2.conf, ..}
/logs/{app1.log, app2.log...}
The script use configuration file for each web app, configuration file
looks as below:
---------------
url = https://www.example.com
sla = 10
logfile = example.com.prod
-----------
The script looks as follow:
-------------------------------
#!/usr/bin/perl
use strict;
use warnings;
use AppConfig;
use Parallel::ForkManager;
use Log::Log4perl qw(:easy);
use HTTP::Request::Common;
use LWP::UserAgent;
use HTTP::Cookies;
use Benchmark ':hireswallclock';
use Time::HiRes qw ( time alarm sleep );
use IPC::Run('run'); # Not shown the use of it in this script, is
useful to interact with nagios or run any other command line commands
our %LOGFILE;
our $APP_HOME = '/usr/local/application';
our $HTTPRESP = 'httpresp';
$LOGFILE{file} = $APP_HOME . "/" . $HTTPRESP . "/". 'logs/
generic.log';
my $MAX_PROC =
100; # restricting to 100 process at this moment, but can be
modified any time
$SIG{ALRM} = \&response_sla;
my $confdir = "$APP_HOME/$HTTPRESP/conf";
my $pm = new Parallel::ForkManager($MAX_PROC);
my $cnfhs = get_configurations();
foreach my $key ( keys %$cnfhs ) {
my $conf = $cnfhs->{$key};
my $pid = $pm->start and next;
my $logger = logger( $conf->get('logfile') );
crawl_sites( $conf, $logger );
$pm->finish;
}
$pm->wait_all_children;
sub get_configurations {
my @confs = glob( $confdir . "/*.conf" );
my $confhash = {};
foreach my $cnf (@confs) {
my $config = AppConfig->new();
$config->define('name=s');
$config->define('url=s');
$config->define('sla=s');
$config->define('logfile=s');
$config->define('appname=s');
$config->file($cnf);
$confhash->{$cnf} = $config;
}
return $confhash;
}
sub logger {
my $logfilename = shift;
$LOGFILE{file} = $logfilename;
my $conf = q(
log4perl.logger = INFO, FileApp
log4perl.appender.FileApp =
Log::Log4perl::Appender::File
log4perl.appender.FileApp.filename = sub {getLogfilename();}
log4perl.appender.FileApp.layout = PatternLayout
log4perl.appender.FileApp.layout.ConversionPattern = %d> %m%n
);
# Initialize logging behaviour
Log::Log4perl->init( \$conf );
# Obtain a logger instance
my $logger = get_logger();
return $logger;
}
sub getLogfilename {
return "$APP_HOME/$HTTPRESP/logs/" . $LOGFILE{file} . ".log";
}
sub crawl_sites {
my ( $conf, $logger ) = @_;
my $sla = $conf->get('sla');
my $url = $conf->get('url');
eval {
alarm($sla);
get_response( $url, $logger );
alarm(0);
};
if ( $@ =~ /SLA: DID NOT MET/ ) {
print "SLA DID NOT MET\n";
//code_to_interact_with_nagios
}else {
//code_to_interact_with_nagios
}
}
sub get_response {
my ( $url, $logger ) = @_;
$logger->info("Started monitoring: $url ");
my $ua = new LWP::UserAgent;
$ua->cookie_jar( HTTP::Cookies->new() );
$ua->agent(
'Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.2.18) Gecko/
20110614 Firefox/3.6.18'
);
$ua->ssl_opts( verify_hostname => 0 ); ##Skip verifying SSL
Certificate
my $t1 = Benchmark->new;
my $response = $ua->request( GET $url);
if ( $response->is_success ) {
$logger->info("SUCCESS: Got the response"); # or whatever
}
else {
$logger->info( "ERROR: the response was, " . $response-
>status_line );
}
my $t2 = Benchmark->new;
my $td = timediff( $t2, $t1 );
print "Total Response time: " . timestr($td) . "\n";
$logger->info( "Total Response time: " . timestr($td) );
}
sub response_sla {
die "SLA: DID NOT MET";
}
--------------------------------
Help me to improve this program - performance, scale to large (say 1k
or 2 k web apps) number of apps..
thank you for your time !
--sss
------------------------------
Date: Fri, 07 Oct 2011 15:49:24 -0500
From: Tad McClellan <tadmc@seesig.invalid>
Subject: Re: Help me to Improve
Message-Id: <slrnj8uogh.6n1.tadmc@tadbox.sbcglobal.net>
SSS Develop <sssdevelop@gmail.com> wrote:
> Subject: Help me to Improve
One way to improve would be to put the subject of your
article in the Subject of your article.
--
Tad McClellan
email: perl -le "print scalar reverse qq/moc.liamg\100cm.j.dat/"
The above message is a Usenet post.
I don't recall having given anyone permission to use it on a Web site.
------------------------------
Date: Fri, 07 Oct 2011 15:55:27 -0500
From: Tad McClellan <tadmc@seesig.invalid>
Subject: Re: Help me to Improve
Message-Id: <slrnj8uors.6n1.tadmc@tadbox.sbcglobal.net>
SSS Develop <sssdevelop@gmail.com> wrote:
> our %LOGFILE;
> our $APP_HOME = '/usr/local/application';
> our $HTTPRESP = 'httpresp';
Why have you made these be package variables
rather than the safer lexical variables?
--
Tad McClellan
email: perl -le "print scalar reverse qq/moc.liamg\100cm.j.dat/"
The above message is a Usenet post.
I don't recall having given anyone permission to use it on a Web site.
------------------------------
Date: Fri, 07 Oct 2011 18:47:53 -0500
From: Ben Morrow <ben@morrow.me.uk>
Subject: Re: Help me to Improve
Message-Id: <GISdnZHgbbI0EhLTnZ2dnUVZ8vmdnZ2d@bt.com>
Quoth SSS Develop <sssdevelop@gmail.com>:
> Hello,
>
> The intention to ask question in this forum is to improve this piece
> of code (for performance and other best practices)
I have to say, it's a lot better than a lot of what gets posted here...
> I have couple of Web Applications - need to monitor the HTTP Response
> for them. Decided to use the Perl - the script should fetch the HTTP
> page from Web App within SLA time (Service Level). If the SLA did not
> met - then system should send alert. For sending alert, it interacts
> with command line tools like email/nagios.
<snip>
>
> #!/usr/bin/perl
>
> use strict;
> use warnings;
> use AppConfig;
> use Parallel::ForkManager;
If the performance of this script is an issue, forking may not be the
best solution. It's pretty much always faster to use a non-blocking
single-process (or single-process-per-CPU) approach, using something
like POE. That would require restructuring the whole program, though, so
if P::FM works for you I should stick with it.
> use Log::Log4perl qw(:easy);
> use HTTP::Request::Common;
> use LWP::UserAgent;
> use HTTP::Cookies;
> use Benchmark ':hireswallclock';
> use Time::HiRes qw ( time alarm sleep );
> use IPC::Run('run'); # Not shown the use of it in this script, is
> useful to interact with nagios or run any other command line commands
>
>
> our %LOGFILE;
> our $APP_HOME = '/usr/local/application';
> our $HTTPRESP = 'httpresp';
> $LOGFILE{file} = $APP_HOME . "/" . $HTTPRESP . "/". 'logs/
> generic.log';
I see Tad's already mentioned you're using 'our' where you could be
using 'my'. I would add that there's no need for concatentation when you
can interpolate, and that you can assign directly to a hash too:
my $APP_HOME = '/usr/local/application';
my $HTTPRESP = 'httpresp';
my %LOGFILE = (
file => "$APP_HOME/$HTTPRESP/logs/generic.log",
);
(Whether to use single or double quotes when nothing will be
interpolated is a matter of taste. I prefer double, but many people here
prefer single.)
> my $MAX_PROC =
> 100; # restricting to 100 process at this moment, but can be
> modified any time
>
> $SIG{ALRM} = \&response_sla;
It's a little confusing to refer to a sub all the way down at the bottom
of the file, especially when it's so trivial it doesn't really need a
name:
$SIG{ALRM} = sub {
die "SLA: DID NOT MET";
};
> my $confdir = "$APP_HOME/$HTTPRESP/conf";
> my $pm = new Parallel::ForkManager($MAX_PROC);
It's best to avoid dative method syntax (METHOD OBJECT ARGS or METHOD
CLASS ARGS), at least in part because it encourages the idea that there
is something special about the 'new' method.
my $pm = Parallel::ForkManager->new($MAX_PROC);
(Yes, I know you just copied that from the documentation. Unfortunately
a lot of CPAN documentation uses older, now-discouraged idioms in the
examples.)
> my $cnfhs = get_configurations();
>
> foreach my $key ( keys %$cnfhs ) {
>
> my $conf = $cnfhs->{$key};
You can write that loop as
while (my ($key, $conf) = each %$cnfhs) {
and it'll even be more efficient on really large hashes. (Not enough
people remember about 'each'.)
>
> my $pid = $pm->start and next;
> my $logger = logger( $conf->get('logfile') );
>
> crawl_sites( $conf, $logger );
> $pm->finish;
>
> }
> $pm->wait_all_children;
>
>
> sub get_configurations {
>
> my @confs = glob( $confdir . "/*.conf" );
Passing a value into a sub in a file-scoped global is always worth
avoiding if you can. In this case it's easy: pass it in as a real
parameter instead.
It may seem silly calling get_configurations($confdir) when you know
perfectly well that get_configurations can see that variable, but it
rapidly becomes less silly when you come back six months later and take
it out without remembering some sub half way down the file needed it.
<snip>
> sub logger {
> my $logfilename = shift;
> $LOGFILE{file} = $logfilename;
> my $conf = q(
> log4perl.logger = INFO, FileApp
> log4perl.appender.FileApp =
> Log::Log4perl::Appender::File
> log4perl.appender.FileApp.filename = sub {getLogfilename();}
<...later...>
> sub getLogfilename {
>
> return "$APP_HOME/$HTTPRESP/logs/" . $LOGFILE{file} . ".log";
>
> }
It's not really clear to me what you're trying to do here with
$LOGFILE{file}, but it can almost certainly be done less confusingly.
Since you don't appear to use it anywhere else, is there any reason not
to just put the correct filename straight in the log4perl config?
my $logpath = "$APP_HOME/$HTTPRESP/logs/$logfilename.log";
my $conf = qq(
log4perl.logger = INFO, FileApp
log4perl.appender.FileApp = Log::Log4perl::Appender::File
log4perl.appender.FileApp.filename = $logpath
...
);
(Notice I've changed 'q()' to 'qq()'. I said I preferred double quotes :).)
I'd also want to tidy up this "$APP_HOME/$HTTPRESP" prefix that keeps
turning up. Probably I'd just chdir to that directory and use relative
paths.
> log4perl.appender.FileApp.layout = PatternLayout
> log4perl.appender.FileApp.layout.ConversionPattern = %d> %m%n
> );
>
> # Initialize logging behaviour
> Log::Log4perl->init( \$conf );
>
> # Obtain a logger instance
> my $logger = get_logger();
I see no 'sub get_logger' here...
...oh, I see, it's from Log4perl. I don't think you should be mixing the
normal and the 'easy' interfaces like that. Since you've got as far as
setting up a custom logger config, use the real method so people reading
the code have some idea what's going on:
return Log::Log4perl->get_logger();
> return $logger;
>
> }
>
>
> sub crawl_sites {
> my ( $conf, $logger ) = @_;
> my $sla = $conf->get('sla');
> my $url = $conf->get('url');
> eval {
> alarm($sla);
Once we get as far as this 'alarm' statement, we've entirely forgotten
about the $SIG{ALRM} assignment at the top of the file that said what
the alarm will actually *do*. It's also better, where possible, to write
subs so they don't rely on or change global values. Generally this means
that if you need to use one of the magic Perl globals, you need to
'local' it.
eval {
local $SIG{ALRM} = sub { die "SLA NOT MET" };
alarm($sla);
> get_response( $url, $logger );
> alarm(0);
You have a race condition here. It's entirely possible the alarm will
fire after get_response has received a successful response but before it
has returned and the alarm has been deactivated. In this case, you may
not care (if it was that close to the deadline you may want to count it
as 'late' anyway), but it needs considering. If you have, in fact,
considered it, you should put in a comment so you remember not to
consider it again :).
> };
You need to cancel the alarm here, as well. get_response may die for
some reason other than an alarm, and if it does the alarm will still go
off, but nothing will catch the exception. (There is another race here,
of course, but it's rather hard to avoid. Alarms are tricky.)
<snip>
> sub get_response {
> my ( $url, $logger ) = @_;
>
> $logger->info("Started monitoring: $url ");
> my $ua = new LWP::UserAgent;
> $ua->cookie_jar( HTTP::Cookies->new() );
> $ua->agent(
> 'Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.2.18) Gecko/
> 20110614 Firefox/3.6.18'
> );
> $ua->ssl_opts( verify_hostname => 0 ); ##Skip verifying SSL
> Certificate
You don't need to re-do all this every time. Create a LWP::UA object as
part of your script initialization, then pass it in to get_response.
> my $t1 = Benchmark->new;
>
> my $response = $ua->request( GET $url);
> if ( $response->is_success ) {
> $logger->info("SUCCESS: Got the response"); # or whatever
> }
> else {
> $logger->info( "ERROR: the response was, " . $response-
> >status_line );
> }
> my $t2 = Benchmark->new;
> my $td = timediff( $t2, $t1 );
> print "Total Response time: " . timestr($td) . "\n";
> $logger->info( "Total Response time: " . timestr($td) );
Since you're timing the response anyway, it's probably better to rely on
that measurement, rather than the alarm, to see whether it's gone over
its SLA. You might still want to set an alarm for something like twice
the SLA, just in case the request never returns for some reason (though
LWP will timeout for you eventually).
You might also want to look at LWPx::TimedHTTP, which gives detailed
timings of the various stages of the request cycle.
Ben
------------------------------
Date: Sat, 8 Oct 2011 00:07:39 -0700 (PDT)
From: SSS Develop <sssdevelop@gmail.com>
Subject: Re: Help me to Improve
Message-Id: <d17f7bd5-5803-4925-88ad-916260104cf8@j19g2000vbn.googlegroups.com>
Thank you so much Ben - this was the best feedback/review i got. I was
not expecting such a detailed help. I am so happy and thank you so
much !
I have some comments below. I will correct the code and post the final
version here later.
On Oct 8, 4:47=A0am, Ben Morrow <b...@morrow.me.uk> wrote:
> Quoth SSS Develop <sssdeve...@gmail.com>:
>
> > Hello,
>
> > The intention to ask question in this forum is to improve this piece
> > of code (for performance and other best practices)
>
> I have to say, it's a lot better than a lot of what gets posted here...
>
>
>
> > I have couple of Web Applications - need to monitor the HTTP Response
> > for them. Decided to use the Perl - the script should fetch the HTTP
> > page from Web App within SLA =A0time (Service Level). If the SLA did no=
t
> > met - then system should send alert. For sending alert, it interacts
> > with command line tools like email/nagios.
> <snip>
>
> > #!/usr/bin/perl
>
> > use strict;
> > use warnings;
> > use AppConfig;
> > use Parallel::ForkManager;
>
> If the performance of this script is an issue, forking may not be the
> best solution. It's pretty much always faster to use a non-blocking
> single-process (or single-process-per-CPU) approach, using something
> like POE. That would require restructuring the whole program, though, so
> if P::FM works for you I should stick with it.
>
> > use Log::Log4perl qw(:easy);
> > use HTTP::Request::Common;
> > use LWP::UserAgent;
> > use HTTP::Cookies;
> > use Benchmark ':hireswallclock';
> > use Time::HiRes qw ( time alarm sleep );
> > use IPC::Run('run'); =A0 # Not shown the use of it in this script, is
> > useful to interact with nagios or run any other command line commands
>
> > our %LOGFILE;
> > our $APP_HOME =3D '/usr/local/application';
> > our $HTTPRESP =3D 'httpresp';
> > $LOGFILE{file} =3D =A0$APP_HOME . "/" . $HTTPRESP . "/". 'logs/
> > generic.log';
>
> I see Tad's already mentioned you're using 'our' where you could be
> using 'my'. I would add that there's no need for concatentation when you
> can interpolate, and that you can assign directly to a hash too:
>
> =A0 =A0 my $APP_HOME =A0 =A0=3D '/usr/local/application';
> =A0 =A0 my $HTTPRESP =A0 =A0=3D 'httpresp';
> =A0 =A0 my %LOGFILE =A0 =A0 =3D (
> =A0 =A0 =A0 =A0 file =A0 =A0=3D> "$APP_HOME/$HTTPRESP/logs/generic.log",
> =A0 =A0 );
>
> (Whether to use single or double quotes when nothing will be
> interpolated is a matter of taste. I prefer double, but many people here
> prefer single.)
>
> > my $MAX_PROC =3D
> > =A0 100; # restricting to 100 process at this moment, but can be
> > modified any time
>
> > $SIG{ALRM} =3D \&response_sla;
>
> It's a little confusing to refer to a sub all the way down at the bottom
> of the file, especially when it's so trivial it doesn't really need a
> name:
>
> =A0 =A0 $SIG{ALRM} =3D sub {
> =A0 =A0 =A0 =A0 die "SLA: DID NOT MET";
> =A0 =A0 };
>
> > my $confdir =3D "$APP_HOME/$HTTPRESP/conf";
> > my $pm =A0 =A0 =A0=3D new Parallel::ForkManager($MAX_PROC);
>
> It's best to avoid dative method syntax (METHOD OBJECT ARGS or METHOD
> CLASS ARGS), at least in part because it encourages the idea that there
> is something special about the 'new' method.
>
> =A0 =A0 my $pm =3D Parallel::ForkManager->new($MAX_PROC);
>
> (Yes, I know you just copied that from the documentation. Unfortunately
> a lot of CPAN documentation uses older, now-discouraged idioms in the
> examples.)
>
> > my $cnfhs =3D get_configurations();
>
> > foreach my $key ( keys %$cnfhs ) {
>
> > =A0 =A0 my $conf =3D $cnfhs->{$key};
>
> You can write that loop as
>
> =A0 =A0 while (my ($key, $conf) =3D each %$cnfhs) {
>
> and it'll even be more efficient on really large hashes. (Not enough
> people remember about 'each'.)
>
>
>
> > =A0 =A0 my $pid =3D $pm->start and next;
> > =A0 =A0 my $logger =3D logger( $conf->get('logfile') );
>
> > =A0 =A0 crawl_sites( $conf, $logger );
> > =A0 =A0 $pm->finish;
>
> > }
> > $pm->wait_all_children;
>
> > sub get_configurations {
>
> > =A0 =A0 my @confs =A0 =A0=3D glob( $confdir . "/*.conf" );
>
> Passing a value into a sub in a file-scoped global is always worth
> avoiding if you can. In this case it's easy: pass it in as a real
> parameter instead.
>
> It may seem silly calling get_configurations($confdir) when you know
> perfectly well that get_configurations can see that variable, but it
> rapidly becomes less silly when you come back six months later and take
> it out without remembering some sub half way down the file needed it.
>
> <snip>
>
> > sub logger {
> > =A0 =A0 my $logfilename =3D shift;
> > =A0 =A0 $LOGFILE{file} =3D $logfilename;
> > =A0 =A0 my $conf =3D q(
> > =A0 =A0 =A0 =A0 log4perl.logger =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0=
=3D INFO, FileApp
> > =A0 =A0 =A0 =A0 log4perl.appender.FileApp =A0 =A0 =A0 =A0 =A0=3D
> > Log::Log4perl::Appender::File
> > =A0 =A0 =A0 =A0 log4perl.appender.FileApp.filename =3D sub {getLogfilen=
ame();}
>
> <...later...>
>
> > sub getLogfilename {
>
> > =A0 =A0 return "$APP_HOME/$HTTPRESP/logs/" . $LOGFILE{file} . ".log";
>
> > }
>
> It's not really clear to me what you're trying to do here with
> $LOGFILE{file}, but it can almost certainly be done less confusingly.
> Since you don't appear to use it anywhere else, is there any reason not
> to just put the correct filename straight in the log4perl config?
>
[sssdevelop] I am creating log file for each forked process (per web
app one log file). method logger accepts logfile name as arguments,
that's used to change the "file" value of LOGFILE, thats then used
inside getLogfilename().
I really wanted to interpolate logfilename in appender. Now i got the
clue, i will use "qq" instead of single "q" :)
> =A0 =A0 my $logpath =3D "$APP_HOME/$HTTPRESP/logs/$logfilename.log";
> =A0 =A0 my $conf =A0 =A0=3D qq(
> =A0 =A0 =A0 =A0 log4perl.logger =A0 =A0 =A0 =A0 =A0 =A0 =3D INFO, FileApp
> =A0 =A0 =A0 =A0 log4perl.appender.FileApp =A0 =3D Log::Log4perl::Appender=
::File
> =A0 =A0 =A0 =A0 log4perl.appender.FileApp.filename =3D $logpath
> =A0 =A0 =A0 =A0 ...
> =A0 =A0 );
>
> (Notice I've changed 'q()' to 'qq()'. I said I preferred double quotes :)=
.)
>
> I'd also want to tidy up this "$APP_HOME/$HTTPRESP" prefix that keeps
> turning up. Probably I'd just chdir to that directory and use relative
> paths.
>
> > =A0 =A0 =A0 =A0 log4perl.appender.FileApp.layout =A0 =3D PatternLayout
> > =A0 =A0 =A0 =A0 log4perl.appender.FileApp.layout.ConversionPattern =3D =
%d> %m%n
> > =A0 =A0 );
>
> > =A0 =A0 # Initialize logging behaviour
> > =A0 =A0 Log::Log4perl->init( \$conf );
>
> > =A0 =A0 # Obtain a logger instance
> > =A0 =A0 my $logger =3D get_logger();
>
> I see no 'sub get_logger' here...
>
> ...oh, I see, it's from Log4perl. I don't think you should be mixing the
> normal and the 'easy' interfaces like that. Since you've got as far as
> setting up a custom logger config, use the real method so people reading
> the code have some idea what's going on:
>
> =A0 =A0 return Log::Log4perl->get_logger();
>
> > =A0 =A0 return $logger;
>
> > }
>
[sssdevelop] - yup, agree with this. I will change it!
> > sub crawl_sites {
> > =A0 =A0 my ( $conf, $logger ) =3D @_;
> > =A0 =A0 my $sla =3D $conf->get('sla');
> > =A0 =A0 my $url =3D $conf->get('url');
> > =A0 =A0 eval {
> > =A0 =A0 =A0 =A0 alarm($sla);
>
> Once we get as far as this 'alarm' statement, we've entirely forgotten
> about the $SIG{ALRM} assignment at the top of the file that said what
> the alarm will actually *do*. It's also better, where possible, to write
> subs so they don't rely on or change global values. Generally this means
> that if you need to use one of the magic Perl globals, you need to
> 'local' it.
>
> =A0 =A0 eval {
> =A0 =A0 =A0 =A0 local $SIG{ALRM} =3D sub { die "SLA NOT MET" };
> =A0 =A0 =A0 =A0 alarm($sla);
>
> > =A0 =A0 =A0 =A0 get_response( $url, $logger );
> > =A0 =A0 =A0 =A0 alarm(0);
>
[sssdevelop] Now i see the importance of this, thanks for this
advice.
> You have a race condition here. It's entirely possible the alarm will
> fire after get_response has received a successful response but before it
> has returned and the alarm has been deactivated. In this case, you may
> not care (if it was that close to the deadline you may want to count it
> as 'late' anyway), but it needs considering. If you have, in fact,
> considered it, you should put in a comment so you remember not to
> consider it again :).
>
> > =A0 =A0 };
>
> You need to cancel the alarm here, as well. get_response may die for
> some reason other than an alarm, and if it does the alarm will still go
> off, but nothing will catch the exception. (There is another race here,
> of course, but it's rather hard to avoid. Alarms are tricky.)
>
[sssdevelop] Ah.. i did not put much thought on race happening here.
Need to work on this. this was good advice here :)
> <snip>
>
> > sub get_response {
> > =A0 =A0 my ( $url, $logger ) =3D @_;
>
> > =A0 =A0 $logger->info("Started monitoring: $url ");
> > =A0 =A0 my $ua =3D new LWP::UserAgent;
> > =A0 =A0 $ua->cookie_jar( HTTP::Cookies->new() );
> > =A0 =A0 $ua->agent(
> > 'Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.2.18) Gecko/
> > 20110614 Firefox/3.6.18'
> > =A0 =A0 );
> > =A0 =A0 $ua->ssl_opts( verify_hostname =3D> 0 ); =A0 =A0##Skip verifyin=
g SSL
> > Certificate
>
> You don't need to re-do all this every time. Create a LWP::UA object as
> part of your script initialization, then pass it in to get_response.
>
[sssdevelop] yup, will add single LWP::UA object ! this is helpful.
> > =A0 =A0 my $t1 =3D Benchmark->new;
>
> > =A0 =A0 my $response =3D $ua->request( GET $url);
> > =A0 =A0 if ( $response->is_success ) {
> > =A0 =A0 =A0 =A0 $logger->info("SUCCESS: Got the response"); =A0 =A0# or=
whatever
> > =A0 =A0 }
> > =A0 =A0 else {
> > =A0 =A0 =A0 =A0 $logger->info( "ERROR: the response was, " . $response-
> > >status_line );
> > =A0 =A0 }
> > =A0 =A0 my $t2 =3D Benchmark->new;
> > =A0 =A0 my $td =3D timediff( $t2, $t1 );
> > =A0 =A0 print "Total Response time: " . timestr($td) . "\n";
> > =A0 =A0 $logger->info( "Total Response time: " . timestr($td) );
>
> Since you're timing the response anyway, it's probably better to rely on
> that measurement, rather than the alarm, to see whether it's gone over
> its SLA. You might still want to set an alarm for something like twice
> the SLA, just in case the request never returns for some reason (though
> LWP will timeout for you eventually).
>
> You might also want to look at LWPx::TimedHTTP, which gives detailed
> timings of the various stages of the request cycle.
>
[sssdevelop] - thanks, will surely check this LWPx::TimedHTTP.
Ben, appreciate your help and thank you so much for
your time.
----sssdevelop
> Ben
------------------------------
Date: Fri, 7 Oct 2011 23:29:41 +0200
From: "MARK" <marko.toplica.makni.ovo.@gmail.com>
Subject: how to start perl on android tablet?
Message-Id: <j6nqv7$5db$1@l01news1.ot.hr>
how to start perl on android tablet?
TNX
------------------------------
Date: Fri, 7 Oct 2011 14:45:56 -0700
From: Keith Keller <kkeller-usenet@wombat.san-francisco.ca.us>
Subject: Re: how to start perl on android tablet?
Message-Id: <lh84m8xl76.ln2@goaway.wombat.san-francisco.ca.us>
On 2011-10-07, MARK <marko.toplica.makni.ovo> wrote:
> how to start perl on android tablet?
http://lmgtfy.com/?q=perl+android
--keith
--
kkeller-usenet@wombat.san-francisco.ca.us
(try just my userid to email me)
AOLSFAQ=http://www.therockgarden.ca/aolsfaq.txt
see X- headers for PGP signature information
------------------------------
Date: Fri, 07 Oct 2011 02:25:57 -0500
From: tadmc@seesig.invalid
Subject: Posting Guidelines for comp.lang.perl.misc ($Revision: 1.9 $)
Message-Id: <_Nadnexz6b0YNBPTnZ2dnUVZ5sednZ2d@giganews.com>
Outline
Before posting to comp.lang.perl.misc
Must
- Check the Perl Frequently Asked Questions (FAQ)
- Check the other standard Perl docs (*.pod)
Really Really Should
- Lurk for a while before posting
- Search a Usenet archive
If You Like
- Check Other Resources
Posting to comp.lang.perl.misc
Is there a better place to ask your question?
- Question should be about Perl, not about the application area
How to participate (post) in the clpmisc community
- Carefully choose the contents of your Subject header
- Use an effective followup style
- Speak Perl rather than English, when possible
- Ask perl to help you
- Do not re-type Perl code
- Provide enough information
- Do not provide too much information
- Do not post binaries, HTML, or MIME
Social faux pas to avoid
- Asking a Frequently Asked Question
- Asking a question easily answered by a cursory doc search
- Asking for emailed answers
- Beware of saying "doesn't work"
- Sending a "stealth" Cc copy
Be extra cautious when you get upset
- Count to ten before composing a followup when you are upset
- Count to ten after composing and before posting when you are upset
-----------------------------------------------------------------
Posting Guidelines for comp.lang.perl.misc ($Revision: 1.9 $)
This newsgroup, commonly called clpmisc, is a technical newsgroup
intended to be used for discussion of Perl related issues (except job
postings), whether it be comments or questions.
As you would expect, clpmisc discussions are usually very technical in
nature and there are conventions for conduct in technical newsgroups
going somewhat beyond those in non-technical newsgroups.
The article at:
http://www.catb.org/~esr/faqs/smart-questions.html
describes how to get answers from technical people in general.
This article describes things that you should, and should not, do to
increase your chances of getting an answer to your Perl question. It is
available in POD, HTML and plain text formats at:
http://www.rehabitation.com/clpmisc.shtml
For more information about netiquette in general, see the "Netiquette
Guidelines" at:
http://andrew2.andrew.cmu.edu/rfc/rfc1855.html
A note to newsgroup "regulars":
Do not use these guidelines as a "license to flame" or other
meanness. It is possible that a poster is unaware of things
discussed here. Give them the benefit of the doubt, and just
help them learn how to post, rather than assume that they do
know and are being the "bad kind" of Lazy.
A note about technical terms used here:
In this document, we use words like "must" and "should" as
they're used in technical conversation (such as you will
encounter in this newsgroup). When we say that you *must* do
something, we mean that if you don't do that something, then
it's unlikely that you will benefit much from this group.
We're not bossing you around; we're making the point without
lots of words.
Do *NOT* send email to the maintainer of these guidelines. It will be
discarded unread. The guidelines belong to the newsgroup so all
discussion should appear in the newsgroup. I am just the secretary that
writes down the consensus of the group.
Before posting to comp.lang.perl.misc
Must
This section describes things that you *must* do before posting to
clpmisc, in order to maximize your chances of getting meaningful replies
to your inquiry and to avoid getting flamed for being lazy and trying to
have others do your work.
The perl distribution includes documentation that is copied to your hard
drive when you install perl. Also installed is a program for looking
things up in that (and other) documentation named 'perldoc'.
You should either find out where the docs got installed on your system,
or use perldoc to find them for you. Type "perldoc perldoc" to learn how
to use perldoc itself. Type "perldoc perl" to start reading Perl's
standard documentation.
Check the Perl Frequently Asked Questions (FAQ)
Checking the FAQ before posting is required in Big 8 newsgroups in
general, there is nothing clpmisc-specific about this requirement.
You are expected to do this in nearly all newsgroups.
You can use the "-q" switch with perldoc to do a word search of the
questions in the Perl FAQs.
Check the other standard Perl docs (*.pod)
The perl distribution comes with much more documentation than is
available for most other newsgroups, so in clpmisc you should also
see if you can find an answer in the other (non-FAQ) standard docs
before posting.
It is *not* required, or even expected, that you actually *read* all of
Perl's standard docs, only that you spend a few minutes searching them
before posting.
Try doing a word-search in the standard docs for some words/phrases
taken from your problem statement or from your very carefully worded
"Subject:" header.
Really Really Should
This section describes things that you *really should* do before posting
to clpmisc.
Lurk for a while before posting
This is very important and expected in all newsgroups. Lurking means
to monitor a newsgroup for a period to become familiar with local
customs. Each newsgroup has specific customs and rituals. Knowing
these before you participate will help avoid embarrassing social
situations. Consider yourself to be a foreigner at first!
Search a Usenet archive
There are tens of thousands of Perl programmers. It is very likely
that your question has already been asked (and answered). See if you
can find where it has already been answered.
One such searchable archive is:
http://groups.google.com/advanced_search
If You Like
This section describes things that you *can* do before posting to
clpmisc.
Check Other Resources
You may want to check in books or on web sites to see if you can
find the answer to your question.
But you need to consider the source of such information: there are a
lot of very poor Perl books and web sites, and several good ones
too, of course.
Posting to comp.lang.perl.misc
There can be 200 messages in clpmisc in a single day. Nobody is going to
read every article. They must decide somehow which articles they are
going to read, and which they will skip.
Your post is in competition with 199 other posts. You need to "win"
before a person who can help you will even read your question.
These sections describe how you can help keep your article from being
one of the "skipped" ones.
Is there a better place to ask your question?
Question should be about Perl, not about the application area
It can be difficult to separate out where your problem really is,
but you should make a conscious effort to post to the most
applicable newsgroup. That is, after all, where you are the most
likely to find the people who know how to answer your question.
Being able to "partition" a problem is an essential skill for
effectively troubleshooting programming problems. If you don't get
that right, you end up looking for answers in the wrong places.
It should be understood that you may not know that the root of your
problem is not Perl-related (the two most frequent ones are CGI and
Operating System related), so off-topic postings will happen from
time to time. Be gracious when someone helps you find a better place
to ask your question by pointing you to a more applicable newsgroup.
How to participate (post) in the clpmisc community
Carefully choose the contents of your Subject header
You have 40 precious characters of Subject to win out and be one of
the posts that gets read. Don't waste them. Take care while
composing them, they are the key that opens the door to getting an
answer.
Spend them indicating what aspect of Perl others will find if they
should decide to read your article.
Do not spend them indicating "experience level" (guru, newbie...).
Do not spend them pleading (please read, urgent, help!...).
Do not spend them on non-Subjects (Perl question, one-word
Subject...)
For more information on choosing a Subject see "Choosing Good
Subject Lines":
http://www.cpan.org/authors/id/D/DM/DMR/subjects.post
Part of the beauty of newsgroup dynamics, is that you can contribute
to the community with your very first post! If your choice of
Subject leads a fellow Perler to find the thread you are starting,
then even asking a question helps us all.
Use an effective followup style
When composing a followup, quote only enough text to establish the
context for the comments that you will add. Always indicate who
wrote the quoted material. Never quote an entire article. Never
quote a .signature (unless that is what you are commenting on).
Intersperse your comments *following* each section of quoted text to
which they relate. Unappreciated followup styles are referred to as
"top-posting", "Jeopardy" (because the answer comes before the
question), or "TOFU" (Text Over, Fullquote Under).
Reversing the chronology of the dialog makes it much harder to
understand (some folks won't even read it if written in that style).
For more information on quoting style, see:
http://web.presby.edu/~nnqadmin/nnq/nquote.html
Speak Perl rather than English, when possible
Perl is much more precise than natural language. Saying it in Perl
instead will avoid misunderstanding your question or problem.
Do not say: I have variable with "foo\tbar" in it.
Instead say: I have $var = "foo\tbar", or I have $var = 'foo\tbar',
or I have $var = <DATA> (and show the data line).
Ask perl to help you
You can ask perl itself to help you find common programming mistakes
by doing two things: enable warnings (perldoc warnings) and enable
"strict"ures (perldoc strict).
You should not bother the hundreds/thousands of readers of the
newsgroup without first seeing if a machine can help you find your
problem. It is demeaning to be asked to do the work of a machine. It
will annoy the readers of your article.
You can look up any of the messages that perl might issue to find
out what the message means and how to resolve the potential mistake
(perldoc perldiag). If you would like perl to look them up for you,
you can put "use diagnostics;" near the top of your program.
Do not re-type Perl code
Use copy/paste or your editor's "import" function rather than
attempting to type in your code. If you make a typo you will get
followups about your typos instead of about the question you are
trying to get answered.
Provide enough information
If you do the things in this item, you will have an Extremely Good
chance of getting people to try and help you with your problem!
These features are a really big bonus toward your question winning
out over all of the other posts that you are competing with.
First make a short (less than 20-30 lines) and *complete* program
that illustrates the problem you are having. People should be able
to run your program by copy/pasting the code from your article. (You
will find that doing this step very often reveals your problem
directly. Leading to an answer much more quickly and reliably than
posting to Usenet.)
Describe *precisely* the input to your program. Also provide example
input data for your program. If you need to show file input, use the
__DATA__ token (perldata.pod) to provide the file contents inside of
your Perl program.
Show the output (including the verbatim text of any messages) of
your program.
Describe how you want the output to be different from what you are
getting.
If you have no idea at all of how to code up your situation, be sure
to at least describe the 2 things that you *do* know: input and
desired output.
Do not provide too much information
Do not just post your entire program for debugging. Most especially
do not post someone *else's* entire program.
Do not post binaries, HTML, or MIME
clpmisc is a text only newsgroup. If you have images or binaries
that explain your question, put them in a publically accessible
place (like a Web server) and provide a pointer to that location. If
you include code, cut and paste it directly in the message body.
Don't attach anything to the message. Don't post vcards or HTML.
Many people (and even some Usenet servers) will automatically filter
out such messages. Many people will not be able to easily read your
post. Plain text is something everyone can read.
Social faux pas to avoid
The first two below are symptoms of lots of FAQ asking here in clpmisc.
It happens so often that folks will assume that it is happening yet
again. If you have looked but not found, or found but didn't understand
the docs, say so in your article.
Asking a Frequently Asked Question
It should be understood that you may have missed the applicable FAQ
when you checked, which is not a big deal. But if the Frequently
Asked Question is worded similar to your question, folks will assume
that you did not look at all. Don't become indignant at pointers to
the FAQ, particularly if it solves your problem.
Asking a question easily answered by a cursory doc search
If folks think you have not even tried the obvious step of reading
the docs applicable to your problem, they are likely to become
annoyed.
If you are flamed for not checking when you *did* check, then just
shrug it off (and take the answer that you got).
Asking for emailed answers
Emailed answers benefit one person. Posted answers benefit the
entire community. If folks can take the time to answer your
question, then you can take the time to go get the answer in the
same place where you asked the question.
It is OK to ask for a *copy* of the answer to be emailed, but many
will ignore such requests anyway. If you munge your address, you
should never expect (or ask) to get email in response to a Usenet
post.
Ask the question here, get the answer here (maybe).
Beware of saying "doesn't work"
This is a "red flag" phrase. If you find yourself writing that,
pause and see if you can't describe what is not working without
saying "doesn't work". That is, describe how it is not what you
want.
Sending a "stealth" Cc copy
A "stealth Cc" is when you both email and post a reply without
indicating *in the body* that you are doing so.
Be extra cautious when you get upset
Count to ten before composing a followup when you are upset
This is recommended in all Usenet newsgroups. Here in clpmisc, most
flaming sub-threads are not about any feature of Perl at all! They
are most often for what was seen as a breach of netiquette. If you
have lurked for a bit, then you will know what is expected and won't
make such posts in the first place.
But if you get upset, wait a while before writing your followup. I
recommend waiting at least 30 minutes.
Count to ten after composing and before posting when you are upset
After you have written your followup, wait *another* 30 minutes
before committing yourself by posting it. You cannot take it back
once it has been said.
AUTHOR
Tad McClellan and many others on the comp.lang.perl.misc newsgroup.
--
Tad McClellan
email: perl -le "print scalar reverse qq/moc.liamg\100cm.j.dat/"
The above message is a Usenet post.
I don't recall having given anyone permission to use it on a Web site.
------------------------------
Date: 6 Apr 2001 21:33:47 GMT (Last modified)
From: Perl-Users-Request@ruby.oce.orst.edu (Perl-Users-Digest Admin)
Subject: Digest Administrivia (Last modified: 6 Apr 01)
Message-Id: <null>
Administrivia:
To submit articles to comp.lang.perl.announce, send your article to
clpa@perl.com.
Back issues are available via anonymous ftp from
ftp://cil-www.oce.orst.edu/pub/perl/old-digests.
#For other requests pertaining to the digest, send mail to
#perl-users-request@ruby.oce.orst.edu. Do not waste your time or mine
#sending perl questions to the -request address, I don't have time to
#answer them even if I did know the answer.
------------------------------
End of Perl-Users Digest V11 Issue 3514
***************************************
