LWP::UserAgent::DetermUser(Contributed Perl DocumLWP::UserAgent::Determined(3)NAMELWP::UserAgent::Determined - a virtual browser that retries errors
SYNOPSIS
use strict;
use LWP::UserAgent::Determined;
my $browser = LWP::UserAgent::Determined->new;
my $response = $browser->get($url, headers... );
DESCRIPTION
This class works just like LWP::UserAgent (and is based on it, by being
a subclass of it), except that when you use it to get a web page but
run into a possibly-temporary error (like a DNS lookup timeout), it'll
wait a few seconds and retry a few times.
It also adds some methods for controlling exactly what errors are
considered retry-worthy and how many times to wait and for how many
seconds, but normally you needn't bother about these, as the default
settings are relatively sane.
METHODS
This module inherits all of LWP::UserAgent's methods, and adds the
following.
$timing_string = $browser->timing();
$browser->timing( "10,30,90" )
The "timing" method gets or sets the string that controls how many
times it should retry, and how long the pauses should be.
If you specify empty-string, this means not to retry at all.
If you specify a string consisting of a single number, like "10",
that means that if the first request doesn't succeed, then
"$browser->get(...)" (or any other method based on "request" or
"simple_request") should wait 10 seconds and try again (and if that
fails, then it's final).
If you specify a string with several numbers in it (like
"10,30,90"), then that means $browser can retry as that many times
(i.e., one initial try, plus a maximum of the three retries,
because three numbers there), and that it should wait first those
numbers of seconds each time. So "$browser->timing( "10,30,90" )"
basically means:
try the request; return it unless it's a temporary-looking error;
sleep 10;
retry the request; return it unless it's a temporary-looking error;
sleep 30;
retry the request; return it unless it's a temporary-looking error;
sleep 90 the request;
return it;
The default value is "1,3,15".
$http_codes_hr = $browser->codes_to_determinate();
This returns the hash that is the set of HTTP codes that merit a
retry (like 500 and 408, but unlike 404 or 200). You can delete or
add entries like so;
$http_codes_hr = $browser->codes_to_determinate();
delete $http_codes_hr->{408};
$http_codes_hr->{567} = 1;
(You can actually set a whole new hashset with
"$browser->codes_to_determinate($new_hr)", but there's usually no
benefit to that as opposed to the above.)
The current default is 408 (Timeout) plus some 5xx codes.
$browser->before_determined_callback()
$browser->before_determined_callback( \&some_routine );
$browser->after_determined_callback()
$browser->after_determined_callback( \&some_routine );
These read (first two) or set (second two) callbacks that are
called before the actual HTTP/FTP/etc request is made. By default,
these are set to undef, meaning nothing special is called. If you
want to alter try requests, or inspect responses before any
retrying is considered, you can set up these callbacks.
The arguments passed to these routines are:
0: the current $browser object
1: an arrayref to the list of timing pauses (based on
$browser->timing)
2: the duration of the number of seconds we'll pause if this
request fails this time, or undef if this is the last chance.
3: the value of $browser->codes_to_determinate
4: an arrayref of the arguments we pass to
LWP::UserAgent::simple_request (the first of which is the request
object)
(5): And, only for after_determined_callback, the response we just
got.
Example use:
$browser->before_determined_callback( sub {
print "Trying ", $_[4][0]->uri, " ...\n";
});
IMPLEMENTATION
This class works by overriding LWP::UserAgent's "simple_request" method
with its own around-method that just loops. See the source of this
module; it's straightforward. Relatively.
SEE ALSO
LWP, LWP::UserAgent
COPYRIGHT AND DISCLAIMER
Copyright 2004, Sean M. Burke "sburke@cpan.org", all rights reserved.
This program is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.
This program is distributed in the hope that it will be useful, but
without any warranty; without even the implied warranty of
merchantability or fitness for a particular purpose.
AUTHOR
Sean M. Burke, "sburke@cpan.org"
perl v5.14.1 2011-01-03 LWP::UserAgent::Determined(3)
