Provided by: libnet-async-http-perl_0.49-1_all 
NAME
"Net::Async::HTTP" - use HTTP with "IO::Async"
SYNOPSIS
use Future::AsyncAwait;
use IO::Async::Loop;
use Net::Async::HTTP;
use URI;
my $loop = IO::Async::Loop->new();
my $http = Net::Async::HTTP->new();
$loop->add( $http );
my $response = await $http->do_request(
uri => URI->new( "http://www.cpan.org/" ),
);
print "Front page of http://www.cpan.org/ is:\n";
print $response->as_string;
DESCRIPTION
This object class implements an asynchronous HTTP user agent. It sends requests to servers, returning
Future instances to yield responses when they are received. The object supports multiple concurrent
connections to servers, and allows multiple requests in the pipeline to any one connection. Normally,
only one such object will be needed per program to support any number of requests.
As well as using futures the module also supports a callback-based interface.
This module optionally supports SSL connections, if IO::Async::SSL is installed. If so, SSL can be
requested either by passing a URI with the "https" scheme, or by passing a true value as the "SSL"
parameter.
Connection Pooling
There are three ways in which connections to HTTP server hosts are managed by this object, controlled by
the value of "max_connections_per_host". This controls when new connections are established to servers,
as compared to waiting for existing connections to be free, as new requests are made to them.
They are:
max_connections_per_host = 1
This is the default setting. In this mode, there will be one connection per host on which there are
active or pending requests. If new requests are made while an existing one is outstanding, they will be
queued to wait for it.
If pipelining is active on the connection (because both the "pipeline" option is true and the
connection is known to be an HTTP/1.1 server), then requests will be pipelined into the connection
awaiting their response. If not, they will be queued awaiting a response to the previous before sending
the next.
max_connections_per_host > 1
In this mode, there can be more than one connection per host. If a new request is made, it will try to
re-use idle connections if there are any, or if they are all busy it will create a new connection to
the host, up to the configured limit.
max_connections_per_host = 0
In this mode, there is no upper limit to the number of connections per host. Every new request will
try to reuse an idle connection, or else create a new one if all the existing ones are busy.
These modes all apply per hostname / server port pair; they do not affect the behaviour of connections
made to differing hostnames, or differing ports on the same hostname.
PARAMETERS
The following named parameters may be passed to "new" or "configure":
user_agent => STRING
A string to set in the "User-Agent" HTTP header. If not supplied, one will be constructed that declares
"Net::Async::HTTP" and the version number.
headers => ARRAY or HASH
Since version 0.45.
A set of extra headers to apply to every outgoing request. May be specified either as an even-sized array
containing key/value pairs, or a hash.
Individual header values may be added or changed without replacing the entire set by using the configure
method and passing a key called "+headers":
$http->configure( +headers => { One_More => "Key" } );
max_redirects => INT
Optional. How many levels of redirection to follow. If not supplied, will default to 3. Give 0 to disable
redirection entirely.
max_in_flight => INT
Optional. The maximum number of in-flight requests to allow per host when pipelining is enabled and
supported on that host. If more requests are made over this limit they will be queued internally by the
object and not sent to the server until responses are received. If not supplied, will default to 4. Give
0 to disable the limit entirely.
max_connections_per_host => INT
Optional. Controls the maximum number of connections per hostname/server port pair, before requests will
be queued awaiting one to be free. Give 0 to disable the limit entirely. See also the "Connection
Pooling" section documented above.
Currently, if not supplied it will default to 1. However, it has been found in practice that most
programs will raise this limit to something higher, perhaps 3 or 4. Therefore, a future version of this
module may set a higher value.
To test if your application will handle this correctly, you can set a different default by setting an
environment variable:
$ NET_ASYNC_HTTP_MAXCONNS=3 perl ...
timeout => NUM
Optional. How long in seconds to wait before giving up on a request. If not supplied then no default will
be applied, and no timeout will take place.
stall_timeout => NUM
Optional. How long in seconds to wait after each write or read of data on a socket, before giving up on a
request. This may be more useful than "timeout" on large-file operations, as it will not time out
provided that regular progress is still being made.
proxy_host => STRING
proxy_port => INT
Since version 0.10.
proxy_path => PATH
Since version 0.49.
Optional. Default values to apply to each "request" method.
cookie_jar => HTTP::Cookies
Optional. A reference to a HTTP::Cookies object. Will be used to set cookies in requests and store them
from responses.
pipeline => BOOL
Optional. If false, disables HTTP/1.1-style request pipelining.
close_after_request => BOOL
Since version 0.45.
Optional. If true, will set the "Connection: close" header on outgoing requests and disable pipelining,
thus making every request use a new connection.
family => INT
local_host => STRING
local_port => INT
local_addrs => ARRAY
local_addr => HASH or ARRAY
Optional. Parameters to pass on to the "connect" method used to connect sockets to HTTP servers. Sets the
socket family and local socket address to "bind()" to. For more detail, see the documentation in
IO::Async::Connector.
fail_on_error => BOOL
Optional. Affects the behaviour of response handling when a "4xx" or "5xx" response code is received.
When false, these responses will be processed as other responses and yielded as the result of the future,
or passed to the "on_response" callback. When true, such an error response causes the future to fail, or
the "on_error" callback to be invoked.
The HTTP response and request objects will be passed as well as the code and message, and the failure
name will be "http".
( $code_message, "http", $response, $request ) = $f->failure
$on_error->( "$code $message", $response, $request )
read_len => INT
write_len => INT
Optional. Used to set the reading and writing buffer lengths on the underlying "IO::Async::Stream"
objects that represent connections to the server. If not define, a default of 64 KiB will be used.
ip_tos => INT or STRING
Optional. Used to set the "IP_TOS" socket option on client sockets. If given, should either be a
"IPTOS_*" constant, or one of the string names "lowdelay", "throughput", "reliability" or "mincost". If
undefined or left absent, no option will be set.
decode_content => BOOL
Optional. If true, incoming responses that have a recognised "Content-Encoding" are handled by the
module, and decompressed content is passed to the body handling callback or returned in the
"HTTP::Response". See "CONTENT DECODING" below for details of which encoding types are recognised. When
this option is enabled, outgoing requests also have the "Accept-Encoding" header added to them if it does
not already exist.
Currently the default is false, because this behaviour is new, but it may default to true in a later
version. Applications which care which behaviour applies should set this to a defined value to ensure it
doesn't change.
SSL_*
Additionally, any parameters whose names start with "SSL_" will be stored and passed on requests to
perform SSL requests. This simplifies configuration of common SSL parameters.
require_SSL => BOOL
Optional. If true, then any attempt to make a request that does not use SSL (either by calling "request",
or as a result of a redirection) will immediately fail.
SOCKS_*
Since version 0.42.
Additionally, any parameters whose names start with "SOCKS_" will be stored and used by Net::Async::SOCKS
to establish connections via a configured proxy.
METHODS
The following methods documented in an "await" expression return Future instances.
When returning a Future, the following methods all indicate HTTP-level errors using the Future failure
name of "http". If the error relates to a specific response it will be included. The original request is
also included.
$f->fail( $message, "http", $response, $request )
do_request
$response = await $http->do_request( %args );
Send an HTTP request to a server, returning a Future that will yield the response. The request may be
represented by an HTTP::Request object, or a URI object, depending on the arguments passed.
The following named arguments are used for "HTTP::Request"s:
request => HTTP::Request
A reference to an "HTTP::Request" object
host => STRING
Hostname of the server to connect to
port => INT or STRING
Optional. Port number or service of the server to connect to. If not defined, will default to
"http" or "https" depending on whether SSL is being used.
family => INT or STRING
Optional. Restricts the socket family for connecting. If not defined, will default to the
globally-configured value in the object. The value may either be a "PF_*" constant directly, or
the lowercase name of one such as "inet".
SSL => BOOL
Optional. If true, an SSL connection will be used.
The following named arguments are used for "URI" requests:
uri => URI or STRING
A reference to a "URI" object, or a plain string giving the request URI. If the scheme is "https"
then an SSL connection will be used.
method => STRING
Optional. The HTTP method name. If missing, "GET" is used.
content => STRING or ARRAY ref
Optional. The body content to use for "PUT" or "POST" requests.
If this is a plain scalar it will be used directly, and a "content_type" field must also be
supplied to describe it.
If this is an ARRAY ref and the request method is "POST", it will be form encoded. It should
contain an even-sized list of field names and values. For more detail see "POST" in
HTTP::Request::Common.
content_type => STRING
The type of non-form data "content".
user => STRING
pass => STRING
Optional. If both are given, the HTTP Basic Authorization header will be sent with these details.
headers => ARRAY|HASH
Optional. If provided, contains additional HTTP headers to set on the constructed request object.
If provided as an ARRAY reference, it should contain an even-sized list of name/value pairs.
proxy_host => STRING
proxy_port => INT
Since version 0.10.
Optional. Override the hostname or port number implied by the URI.
proxy_path => PATH
Since version 0.49.
Optional. Set a UNIX socket path to use as a proxy. To make use of this, also set the "family"
argument to "unix".
For either request type, it takes the following arguments:
request_body => STRING | CODE | Future
Optional. Allows request body content to be generated by a future or callback, rather than being
provided as part of the "request" object. This can either be a plain string, a "CODE" reference
to a generator function, or a future.
As this is passed to the underlying IO::Async::Stream "write" method, the usual semantics apply
here. If passed a "CODE" reference, it will be called repeatedly whenever it's safe to write. The
code should should return "undef" to indicate completion. If passed a "Future" it is expected to
eventually yield the body value.
As with the "content" parameter, the "content_type" field should be specified explicitly in the
request header, as should the content length (typically via the HTTP::Request "content_length"
method). See also examples/PUT.pl.
expect_continue => BOOL
Optional. If true, sets the "Expect" request header to the value "100-continue" and does not send
the "request_body" parameter until a "100 Continue" response is received from the server. If an
error response is received then the "request_body" code, if present, will not be invoked.
on_ready => CODE
Optional. A callback that is invoked once a socket connection is established with the HTTP
server, but before the request is actually sent over it. This may be used by the client code to
inspect the socket, or perform any other operations on it. This code is expected to return a
"Future"; only once that has completed will the request cycle continue. If it fails, that failure
is propagated to the caller.
$f = $on_ready->( $connection )
on_redirect => CODE
Optional. A callback that is invoked if a redirect response is received, before the new location
is fetched. It will be passed the response and the new URL.
$on_redirect->( $response, $location )
on_body_write => CODE
Optional. A callback that is invoked after each successful "syswrite" of the body content. This
may be used to implement an upload progress indicator or similar. It will be passed the total
number of bytes of body content written so far (i.e. excluding bytes consumed in the header).
$on_body_write->( $written )
max_redirects => INT
Optional. How many levels of redirection to follow. If not supplied, will default to the value
given in the constructor.
timeout => NUM
stall_timeout => NUM
Optional. Overrides the object's configured timeout values for this one request. If not
specified, will use the configured defaults.
On a timeout, the returned future will fail with either "timeout" or "stall_timeout" as the
operation name.
( $message, "timeout" ) = $f->failure
do_request (void)
$http->do_request( %args )
When not returning a future, the following extra arguments are used as callbacks instead:
on_response => CODE
A callback that is invoked when a response to this request has been received. It will be passed
an HTTP::Response object containing the response the server sent.
$on_response->( $response )
on_header => CODE
Alternative to "on_response". A callback that is invoked when the header of a response has been
received. It is expected to return a "CODE" reference for handling chunks of body content. This
"CODE" reference will be invoked with no arguments once the end of the request has been reached,
and whatever it returns will be used as the result of the returned "Future", if there is one.
$on_body_chunk = $on_header->( $header )
$on_body_chunk->( $data )
$response = $on_body_chunk->()
on_error => CODE
A callback that is invoked if an error occurs while trying to send the request or obtain the
response. It will be passed an error message.
$on_error->( $message )
If this is invoked because of a received "4xx" or "5xx" error code in an HTTP response, it will
be invoked with the response and request objects as well.
$on_error->( $message, $response, $request )
GET, HEAD, PUT, ...
$response = await $http->GET( $uri, %args );
$response = await $http->HEAD( $uri, %args );
$response = await $http->PUT( $uri, $content, %args );
$response = await $http->POST( $uri, $content, %args );
Since version 0.36.
$response = await $http->PATCH( $uri, $content, %args );
Since version 0.48.
$response = await $http->DELETE( $uri, %args );
Since version 0.49.
Convenient wrappers for performing "GET", "HEAD", "PUT", "POST", "PATCH" or "DELETE" requests with a
"URI" object and few if any other arguments, returning a "Future".
Remember that "POST" with non-form data (as indicated by a plain scalar instead of an "ARRAY" reference
of form data name/value pairs) needs a "content_type" key in %args.
SUBCLASS METHODS
The following methods are intended as points for subclasses to override, to add extra functionallity.
prepare_request
$http->prepare_request( $request )
Called just before the "HTTP::Request" object is sent to the server.
process_response
$http->process_response( $response )
Called after a non-redirect "HTTP::Response" has been received from a server. The originating request
will be set in the object.
CONTENT DECODING
If the required decompression modules are installed and available, compressed content can be decoded. If
the received "Content-Encoding" is recognised and the required module is available, the content is
transparently decoded and the decoded content is returned in the resulting response object, or passed to
the data chunk handler. In this case, the original "Content-Encoding" header will be deleted from the
response, and its value will be available instead as "X-Original-Content-Encoding".
The following content encoding types are recognised by these modules:
• gzip (q=0.7) and deflate (q=0.5)
Recognised if Compress::Raw::Zlib version 2.057 or newer is installed.
• bzip2 (q=0.8)
Recognised if Compress::Bzip2 version 2.10 or newer is installed.
Other content encoding types can be registered by calling the following method
register_decoder
Net::Async::HTTP->register_decoder( $name, $q, $make_decoder )
Registers an encoding type called $name, at the quality value $q. In order to decode this encoding type,
$make_decoder will be invoked with no paramters, and expected to return a CODE reference to perform one
instance of decoding.
$decoder = $make_decoder->()
This decoder will be invoked on string buffers to decode them until the end of stream is reached, when it
will be invoked with no arguments.
$content = $decoder->( $encoded_content )
$content = $decoder->() # EOS
EXAMPLES
Concurrent GET
The "Future"-returning "GET" method makes it easy to await multiple URLs at once, by using the
Future::Utils "fmap_void" utility
use Future::AsyncAwait;
use Future::Utils qw( fmap_void );
my @URLs = ( ... );
my $http = Net::Async::HTTP->new( ... );
$loop->add( $http );
my $future = fmap_void {
my ( $url ) = @_;
$http->GET( $url )
->on_done( sub {
my $response = shift;
say "$url succeeded: ", $response->code;
say " Content-Type:", $response->content_type;
} )
->on_fail( sub {
my $failure = shift;
say "$url failed: $failure";
} );
} foreach => \@URLs,
concurrent => 5;
await $future;
SEE ALSO
• <http://tools.ietf.org/html/rfc2616> - Hypertext Transfer Protocol -- HTTP/1.1
SPONSORS
Parts of this code, or bugfixes to it were paid for by
• SocialFlow <http://www.socialflow.com>
• Shadowcat Systems <http://www.shadow.cat>
• NET-A-PORTER <http://www.net-a-porter.com>
• Cisco <http://www.cisco.com>
AUTHOR
Paul Evans <leonerd@leonerd.org.uk>
perl v5.36.0 2023-10-26 Net::Async::HTTP(3pm)