Provided by: libpoe-component-client-http-perl_0.949-2_all bug

NAME

       POE::Component::Client::HTTP - a HTTP user-agent component

VERSION

       version 0.949

SYNOPSIS

         use POE qw(Component::Client::HTTP);

         POE::Component::Client::HTTP->spawn(
           Agent     => 'SpiffCrawler/0.90',   # defaults to something long
           Alias     => 'ua',                  # defaults to 'weeble'
           From      => 'spiffster@perl.org',  # defaults to undef (no header)
           Protocol  => 'HTTP/0.9',            # defaults to 'HTTP/1.1'
           Timeout   => 60,                    # defaults to 180 seconds
           MaxSize   => 16384,                 # defaults to entire response
           Streaming => 4096,                  # defaults to 0 (off)
           FollowRedirects => 2,               # defaults to 0 (off)
           Proxy     => "http://localhost:80", # defaults to HTTP_PROXY env. variable
           NoProxy   => [ "localhost", "127.0.0.1" ], # defs to NO_PROXY env. variable
           BindAddr  => "12.34.56.78",         # defaults to INADDR_ANY
         );

         $kernel->post(
           'ua',        # posts to the 'ua' alias
           'request',   # posts to ua's 'request' state
           'response',  # which of our states will receive the response
           $request,    # an HTTP::Request object
         );

         # This is the sub which is called when the session receives a
         # 'response' event.
         sub response_handler {
           my ($request_packet, $response_packet) = @_[ARG0, ARG1];

           # HTTP::Request
           my $request_object  = $request_packet->[0];

           # HTTP::Response
           my $response_object = $response_packet->[0];

           my $stream_chunk;
           if (! defined($response_object->content)) {
             $stream_chunk = $response_packet->[1];
           }

           print(
             "*" x 78, "\n",
             "*** my request:\n",
             "-" x 78, "\n",
             $request_object->as_string(),
             "*" x 78, "\n",
             "*** their response:\n",
             "-" x 78, "\n",
             $response_object->as_string(),
           );

           if (defined $stream_chunk) {
             print "-" x 40, "\n", $stream_chunk, "\n";
           }

           print "*" x 78, "\n";
         }

DESCRIPTION

       POE::Component::Client::HTTP is an HTTP user-agent for POE.  It lets other sessions run
       while HTTP transactions are being processed, and it lets several HTTP transactions be
       processed in parallel.

       It supports keep-alive through POE::Component::Client::Keepalive, which in turn uses
       POE::Component::Resolver for asynchronous IPv4 and IPv6 name resolution.

       HTTP client components are not proper objects.  Instead of being created, as most objects
       are, they are "spawned" as separate sessions.  To avoid confusion (and hopefully not cause
       other confusion), they must be spawned with a "spawn" method, not created anew with a
       "new" one.

CONSTRUCTOR

   spawn
       PoCo::Client::HTTP's "spawn" method takes a few named parameters:

       Agent => $user_agent_string
       Agent => \@list_of_agents
         If a UserAgent header is not present in the HTTP::Request, a random one will be used
         from those specified by the "Agent" parameter.  If none are supplied,
         POE::Component::Client::HTTP will advertise itself to the server.

         "Agent" may contain a reference to a list of user agents.  If this is the case,
         PoCo::Client::HTTP will choose one of them at random for each request.

       Alias => $session_alias
         "Alias" sets the name by which the session will be known.  If no alias is given, the
         component defaults to "weeble".  The alias lets several sessions interact with HTTP
         components without keeping (or even knowing) hard references to them.  It's possible to
         spawn several HTTP components with different names.

       ConnectionManager => $poco_client_keepalive
         "ConnectionManager" sets this component's connection pool manager.  It expects the
         connection manager to be a reference to a POE::Component::Client::Keepalive object.  The
         HTTP client component will call "allocate()" on the connection manager itself so you
         should not have done this already.

           my $pool = POE::Component::Client::Keepalive->new(
             keep_alive    => 10, # seconds to keep connections alive
             max_open      => 100, # max concurrent connections - total
             max_per_host  => 20, # max concurrent connections - per host
             timeout       => 30, # max time (seconds) to establish a new connection
           );

           POE::Component::Client::HTTP->spawn(
             # ...
             ConnectionManager => $pool,
             # ...
           );

         See POE::Component::Client::Keepalive for more information, including how to alter the
         connection manager's resolver configuration (for example, to force IPv6 or prefer it
         before IPv4).

       CookieJar => $cookie_jar
         "CookieJar" sets the component's cookie jar.  It expects the cookie jar to be a
         reference to a HTTP::Cookies object.

       From => $admin_address
         "From" holds an e-mail address where the client's administrator and/or maintainer may be
         reached.  It defaults to undef, which means no From header will be included in requests.

       MaxSize => OCTETS
         "MaxSize" specifies the largest response to accept from a server.  The content of larger
         responses will be truncated to OCTET octets.  This has been used to return the
         <head></head> section of web pages without the need to wade through <body></body>.

       NoProxy => [ $host_1, $host_2, ..., $host_N ]
       NoProxy => "host1,host2,hostN"
         "NoProxy" specifies a list of server hosts that will not be proxied.  It is useful for
         local hosts and hosts that do not properly support proxying.  If NoProxy is not
         specified, a list will be taken from the NO_PROXY environment variable.

           NoProxy => [ "localhost", "127.0.0.1" ],
           NoProxy => "localhost,127.0.0.1",

       BindAddr => $local_ip
         Specify "BindAddr" to bind all client sockets to a particular local address.  The value
         of BindAddr will be passed through POE::Component::Client::Keepalive to
         POE::Wheel::SocketFactory (as "bind_address").  See that module's documentation for
         implementation details.

           BindAddr => "12.34.56.78"

       Protocol => $http_protocol_string
         "Protocol" advertises the protocol that the client wishes to see.  Under normal
         circumstances, it should be left to its default value: "HTTP/1.1".

       Proxy => [ $proxy_host, $proxy_port ]
       Proxy => $proxy_url
       Proxy => $proxy_url,$proxy_url,...
         "Proxy" specifies one or more proxy hosts that requests will be passed through.  If not
         specified, proxy servers will be taken from the HTTP_PROXY (or http_proxy) environment
         variable.  No proxying will occur unless Proxy is set or one of the environment
         variables exists.

         The proxy can be specified either as a host and port, or as one or more URLs.  Proxy
         URLs must specify the proxy port, even if it is 80.

           Proxy => [ "127.0.0.1", 80 ],
           Proxy => "http://127.0.0.1:80/",

         "Proxy" may specify multiple proxies separated by commas.  PoCo::Client::HTTP will
         choose proxies from this list at random.  This is useful for load balancing requests
         through multiple gateways.

           Proxy => "http://127.0.0.1:80/,http://127.0.0.1:81/",

       Streaming => OCTETS
         "Streaming" changes allows Client::HTTP to return large content in chunks (of OCTETS
         octets each) rather than combine the entire content into a single HTTP::Response object.

         By default, Client::HTTP reads the entire content for a response into memory before
         returning an HTTP::Response object.  This is obviously bad for applications like
         streaming MP3 clients, because they often fetch songs that never end.  Yes, they go on
         and on, my friend.

         When "Streaming" is set to nonzero, however, the response handler receives chunks of up
         to OCTETS octets apiece.  The response handler accepts slightly different parameters in
         this case.  ARG0 is also an HTTP::Response object but it does not contain response
         content, and ARG1 contains a a chunk of raw response content, or undef if the stream has
         ended.

           sub streaming_response_handler {
             my $response_packet = $_[ARG1];
             my ($response, $data) = @$response_packet;
             print SAVED_STREAM $data if defined $data;
           }

       FollowRedirects => $number_of_hops_to_follow
         "FollowRedirects" specifies how many redirects (e.g. 302 Moved) to follow.  If not
         specified defaults to 0, and thus no redirection is followed.  This maintains
         compatibility with the previous behavior, which was not to follow redirects at all.

         If redirects are followed, a response chain should be built, and can be accessed through
         $response_object->previous(). See HTTP::Response for details here.

       Timeout => $query_timeout
         "Timeout" sets how long POE::Component::Client::HTTP has to process an application's
         request, in seconds.  "Timeout" defaults to 180 (three minutes) if not specified.

         It's important to note that the timeout begins when the component receives an
         application's request, not when it attempts to connect to the web server.

         Timeouts may result from sending the component too many requests at once.  Each request
         would need to be received and tracked in order.  Consider this:

           $_[KERNEL]->post(component => request => ...) for (1..15_000);

         15,000 requests are queued together in one enormous bolus.  The component would receive
         and initialize them in order.  The first socket activity wouldn't arrive until the
         15,000th request was set up.  If that took longer than "Timeout", then the requests that
         have waited too long would fail.

         "ConnectionManager"'s own timeout and concurrency limits also affect how many requests
         may be processed at once.  For example, most of the 15,000 requests would wait in the
         connection manager's pool until sockets become available.  Meanwhile, the "Timeout"
         would be counting down.

         Applications may elect to control concurrency outside the component's "Timeout".  They
         may do so in a few ways.

         The easiest way is to limit the initial number of requests to something more manageable.
         As responses arrive, the application should handle them and start new requests.  This
         limits concurrency to the initial request count.

         An application may also outsource job throttling to another module, such as
         POE::Component::JobQueue.

         In any case, "Timeout" and "ConnectionManager" may be tuned to maximize timeouts and
         concurrency limits.  This may help in some cases.  Developers should be aware that doing
         so will increase memory usage.  POE::Component::Client::HTTP and KeepAlive track
         requests in memory, while applications are free to keep pending requests on disk.

ACCEPTED EVENTS

       Sessions communicate asynchronously with PoCo::Client::HTTP.  They post requests to it,
       and it posts responses back.

   request
       Requests are posted to the component's "request" state.  They include an HTTP::Request
       object which defines the request.  For example:

         $kernel->post(
           'ua', 'request',            # http session alias & state
           'response',                 # my state to receive responses
           GET('http://poe.perl.org'), # a simple HTTP request
           'unique id',                # a tag to identify the request
           'progress',                 # an event to indicate progress
           'http://1.2.3.4:80/'        # proxy to use for this request
         );

       Requests include the state to which responses will be posted.  In the previous example,
       the handler for a 'response' state will be called with each HTTP response.  The "progress"
       handler is optional and if installed, the component will provide progress metrics (see
       sample handler below).  The "proxy" parameter is optional and if not defined, a default
       proxy will be used if configured.  No proxy will be used if neither a default one nor a
       "proxy" parameter is defined.

   pending_requests_count
       There's also a pending_requests_count state that returns the number of requests currently
       being processed.  To receive the return value, it must be invoked with $kernel->call().

         my $count = $kernel->call('ua' => 'pending_requests_count');

       NOTE: Sometimes the count might not be what you expected, because responses are currently
       in POE's queue and you haven't processed them. This could happen if you configure the
       "ConnectionManager"'s concurrency to a high enough value.

   cancel
       Cancel a specific HTTP request.  Requires a reference to the original request (blessed or
       stringified) so it knows which one to cancel.  See "progress handler" below for notes on
       canceling streaming requests.

       To cancel a request based on its blessed HTTP::Request object:

         $kernel->post( component => cancel => $http_request );

       To cancel a request based on its stringified HTTP::Request object:

         $kernel->post( component => cancel => "$http_request" );

   shutdown
       Responds to all pending requests with 408 (request timeout), and then shuts down the
       component and all subcomponents.

SENT EVENTS

   response handler
       In addition to all the usual POE parameters, HTTP responses come with two list references:

         my ($request_packet, $response_packet) = @_[ARG0, ARG1];

       $request_packet contains a reference to the original HTTP::Request object.  This is useful
       for matching responses back to the requests that generated them.

         my $http_request_object = $request_packet->[0];
         my $http_request_tag    = $request_packet->[1]; # from the 'request' post

       $response_packet contains a reference to the resulting HTTP::Response object.

         my $http_response_object = $response_packet->[0];

       Please see the HTTP::Request and HTTP::Response manpages for more information.

   progress handler
       The example progress handler shows how to calculate a percentage of download completion.

         sub progress_handler {
           my $gen_args  = $_[ARG0];    # args passed to all calls
           my $call_args = $_[ARG1];    # args specific to the call

           my $req = $gen_args->[0];    # HTTP::Request object being serviced
           my $tag = $gen_args->[1];    # Request ID tag from.
           my $got = $call_args->[0];   # Number of bytes retrieved so far.
           my $tot = $call_args->[1];   # Total bytes to be retrieved.
           my $oct = $call_args->[2];   # Chunk of raw octets received this time.

           my $percent = $got / $tot * 100;

           printf(
             "-- %.0f%% [%d/%d]: %s\n", $percent, $got, $tot, $req->uri()
           );

           # To cancel the request:
           # $_[KERNEL]->post( component => cancel => $req );
         }

       DEPRECATION WARNING

       The third return argument (the raw octets received) has been deprecated.  Instead of it,
       use the Streaming parameter to get chunks of content in the response handler.

REQUEST CALLBACKS

       The HTTP::Request object passed to the request event can contain a CODE reference as
       "content".  This allows for sending large files without wasting memory.  Your callback
       should return a chunk of data each time it is called, and an empty string when done.
       Don't forget to set the Content-Length header correctly.  Example:

         my $request = HTTP::Request->new( PUT => 'http://...' );

         my $file = '/path/to/large_file';

         open my $fh, '<', $file;

         my $upload_cb = sub {
           if ( sysread $fh, my $buf, 4096 ) {
             return $buf;
           }
           else {
             close $fh;
             return '';
           }
         };

         $request->content_length( -s $file );

         $request->content( $upload_cb );

         $kernel->post( ua => request, 'response', $request );

CONTENT ENCODING AND COMPRESSION

       Transparent content decoding has been disabled as of version 0.84.  This also removes
       support for transparent gzip requesting and decompression.

       To re-enable gzip compression, specify the gzip Content-Encoding and use HTTP::Response's
       decoded_content() method rather than content():

         my $request = HTTP::Request->new(
           GET => "http://www.yahoo.com/", [
             'Accept-Encoding' => 'gzip'
           ]
         );

         # ... time passes ...

         my $content = $response->decoded_content();

       The change in POE::Component::Client::HTTP behavior was prompted by changes in
       HTTP::Response that surfaced a bug in the component's transparent gzip handling.

       Allowing the application to specify and handle content encodings seems to be the most
       reliable and flexible resolution.

       For more information about the problem and discussions regarding the solution, see:
       <http://www.perlmonks.org/?node_id=683833> and
       <http://rt.cpan.org/Ticket/Display.html?id=35538>

CLIENT HEADERS

       POE::Component::Client::HTTP sets its own response headers with additional information.
       All of its headers begin with "X-PCCH".

   X-PCCH-Errmsg
       POE::Component::Client::HTTP may fail because of an internal client error rather than an
       HTTP protocol error.  X-PCCH-Errmsg will contain a human readable reason for client
       failures, should they occur.

       The text of X-PCCH-Errmsg may also be repeated in the response's content.

   X-PCCH-Peer
       X-PCCH-Peer contains the remote IPv4 address and port, separated by a period.  For
       example, "127.0.0.1.8675" represents port 8675 on localhost.

       Proxying will render X-PCCH-Peer nearly useless, since the socket will be connected to a
       proxy rather than the server itself.

       This feature was added at Doreen Grey's request.  Doreen wanted a means to find the remote
       server's address without having to make an additional request.

ENVIRONMENT

       POE::Component::Client::HTTP uses two standard environment variables: HTTP_PROXY and
       NO_PROXY.

       HTTP_PROXY sets the proxy server that Client::HTTP will forward requests through.
       NO_PROXY sets a list of hosts that will not be forwarded through a proxy.

       See the Proxy and NoProxy constructor parameters for more information about these
       variables.

SEE ALSO

       This component is built upon HTTP::Request, HTTP::Response, and POE.  Please see its
       source code and the documentation for its foundation modules to learn more.  If you want
       to use cookies, you'll need to read about HTTP::Cookies as well.

       Also see the test program, t/01_request.t, in the PoCo::Client::HTTP distribution.

BUGS

       There is no support for CGI_PROXY or CgiProxy.

       Secure HTTP (https) proxying is not supported at this time.

       There is no object oriented interface.  See POE::Component::Client::Keepalive and
       POE::Component::Resolver for examples of a decent OO interface.

AUTHOR, COPYRIGHT, & LICENSE

       POE::Component::Client::HTTP is

       · Copyright 1999-2009 Rocco Caputo

       · Copyright 2004 Rob Bloodgood

       · Copyright 2004-2005 Martijn van Beers

       All rights are reserved.  POE::Component::Client::HTTP is free software; you may
       redistribute it and/or modify it under the same terms as Perl itself.

CONTRIBUTORS

       Joel Bernstein solved some nasty race conditions.  Portugal Telecom <http://www.sapo.pt/>
       was kind enough to support his contributions.

       Jeff Bisbee added POD tests and documentation to pass several of them to version 0.79.
       He's a kwalitee-increasing machine!

BUG TRACKER

       https://rt.cpan.org/Dist/Display.html?Queue=POE-Component-Client-HTTP

REPOSITORY

       Github: <http://github.com/rcaputo/poe-component-client-http> .

       Gitorious: <http://gitorious.org/poe-component-client-http> .

OTHER RESOURCES

       <http://search.cpan.org/dist/POE-Component-Client-HTTP/>