NAME
   HTTP::ProxySelector::Persistent - Locally cache and use a list of proxy
   servers for high volume, proxied LWP::UserAgent transactions

VERSION
   Version 0.01

SYNOPSIS
   This module is a fork from HTTP::ProxySelector (written by Eyal Udassin)
   that is modified to:

   * Require less trips to look up proxy lists by caching them locally
   (bandwidth economy and speed).
   * Almost always set your useragent to a valid proxy (reliability).
   * Ensure that you never retry a failed proxy in a subsequent proxy
   selection call (minimum # of timeouts possible).
   * Leave the cache of proxy servers in place after execution for the next
   call to use (persistence).

     use HTTP::ProxySelector;
     use LWP::UserAgent;

     # Instantiate
     my $selector = HTTP::ProxySelector::Persistent->new();
     my $ua = LWP::UserAgent->new();

     # Assign a _ proxy to the UserAgent object.
     $selector->set_proxy($ua);

     # Just in case you need to know the chosen proxy
     print 'Selected proxy: ',$selector->get_proxy(),"\n";

PREREQUISITES
   HTTP::ProxySelector::Persistent requires you to have these perl modules
   installed:

   * BerkeleyDB
   * LWP::UserAgent
   * Date::Manip

PUBLIC METHODS
 new()
   new is the constructor for HTTP::ProxySelector::Persistent objects.

   Returns a new HTTP::ProxySelector::Persistent object.

   Accepts a key-value list of options as arguments. The option keys are:

  db_file
   The full path and filename for the proxy cache database file. You must
   have permission to write in this directory. This option is mandatory, it
   has no default!

  Example :
     $select = HTTP::ProxySelector::Persistent->new( db_file => "/tmp/proxy_cache.bdb" );

  sites
   Reference to a list of sites containing the proxy lists.

  Example :
     $select = HTTP::ProxySelector::Persistent->new( sites => ['http://www.proxylist.com/list.htm'] );

  Default:
     [ 'http://www.multiproxy.org/txt_anon/proxy.txt', 'http://www.samair.ru/proxy/fresh-proxy-list.htm' ]

  update_interval
   How often to update the cached list of proxy servers. Must be readable
   by Date::Manip.

  Example:
     $select = HTTP::ProxySelector::Persistent->new( update_interval => "20 minutes" );

  Default
     "15 minutes"

  testsite
   Destination site to test the proxy with.

  Example :
     $select = HTTP::ProxySelector::Persistent->new( testsite => 'http://yahoo.com' );

  Default
     http://www.google.com

 set_proxy()
   Chooses a proxy at random from the cache database and sets it as the
   proxy for a LWP::UserAgent. Automatically tests the proxy. If the proxy
   fails the test, it removes the proxy from the cache and chooses another
   one until it finds a working proxy. If necessary, this sub will try
   every proxy in the cache database.

   Arguments: A LWP::Useragent object

   Returns: 0 normally, or an error message if it fails

  Example:
     $select->set_proxy( $ua );

 get_proxy()
   Arguments: none.

   Returns: a scalar string containing the address of the selected proxy.

  Example:
     $proxy_address = $select->get_proxy();

 test_proxy()
   Tests the proxy by trying to access a site (specified using the
   "testsite" option when constructing an HTTP::ProxySelector::Persistent
   object).

   Arguments: an LWP::UserAgent object.

   Returns: 0 for success, 1 for failure.

PRIVATE FUNCTIONS
 _fetch_proxies()
   Retrieves the proxy lists, extracts the proxy servers and caches them
   locally in a BerkeleyDB. This sub assumes that the cache database file
   does not exist. If this function were called before the cache database
   file were deleted, you would have duplicate entries in the cache and a
   bunch of old, potentially inoperative proxies stored in the cache. You
   should never have to call this method yourself. The new() method of the
   HTTP::ProxySelector::Persistent object uses this sub when the proxy
   cache database is either expired, malformed, empty or missing.

  Arguments: none.
  Returns:
   0 upon success, or an error message string upon failure.

TODO
   * Code beautification. 1st draft is always rough.

AUTHOR
   Michael Trowbridge, "<michael.a.trowbridge at gmail.com>"

BUGS
   Please report any bugs or feature requests to
   "bug-http-proxyselector-persistent at rt.cpan.org", or through the web
   interface at
   <http://rt.cpan.org/NoAuth/ReportBug.html?Queue=HTTP-ProxySelector-Persi
   stent>. I will be notified, and then you'll automatically be notified of
   progress on your bug as I make changes.

SUPPORT
   You can find documentation for this module with the perldoc command.

       perldoc HTTP::ProxySelector::Persistent

   You can also look for information at:

   * AnnoCPAN: Annotated CPAN documentation
       <http://annocpan.org/dist/HTTP-ProxySelector-Persistent>

   * CPAN Ratings
       <http://cpanratings.perl.org/d/HTTP-ProxySelector-Persistent>

   * RT: CPAN's request tracker
       <http://rt.cpan.org/NoAuth/Bugs.html?Dist=HTTP-ProxySelector-Persist
       ent>

   * Search CPAN
       <http://search.cpan.org/dist/HTTP-ProxySelector-Persistent>

ACKNOWLEDGEMENTS
   This module is a fork from HTTP::ProxySelector v0.02.
   HTTP::ProxySelector v0.02 is copyright 2003 Eyal Udassin.

COPYRIGHT & LICENSE
   Copyright 2007 Michael Trowbridge, all rights reserved.

   This program is free software; you can redistribute it and/or modify it
   under the same terms as Perl itself.

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