POE::Component::Client::HTTP - a HTTP user-agent component
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";
}
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.
If POE::Component::Client::DNS is also installed, Client::HTTP will use it to resolve hosts without blocking. Otherwise it will use gethostbyname(), which may have performance problems.
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.
PoCo::Client::HTTP's spawn method takes a few named parameters:
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 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 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.
CookieJar sets the component's cookie jar. It expects the cookie
jar to be a reference to a HTTP::Cookies object.
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 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 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",
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 advertises the protocol that the client wishes to see.
Under normal circumstances, it should be left to its default value:
"HTTP/1.1".
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 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 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 specifies the amount of time a HTTP request will wait for
an answer. This defaults to 180 seconds (three minutes).
Sessions communicate asynchronously with PoCo::Client::HTTP. They post requests to it, and it posts responses back.
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.
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');
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" );
Responds to all pending requests with 408 (request timeout), and then shuts down the component and all subcomponents.
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.
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 );
}
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.
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 );
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
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.
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.
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::Client::DNS for examples of a decent OO interface.
POE::Component::Client::HTTP is
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.
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!
Rocco may be contacted by e-mail via mailto:rcaputo@cpan.org, and Martijn may be contacted by email via mailto:martijn@cpan.org.
The preferred way to report bugs or requests is through RT though. See http://rt.cpan.org/NoAuth/Bugs.html?Dist=POE-Component-Client-HTTP or mail mailto:bug-POE-Component-Client-HTTP@rt.cpan.org
For questions, try the POE mailing list (poe@perl.org)