Net::Async::HTTP - use HTTP with IO::Async


       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( "" ),
       print "Front page of is:\n";
       print $response->as_string;


    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

    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.


    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

 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

       $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

 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

 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

 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

    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.


    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.


    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.


    The following methods documented in an await expression return Future

    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

       $f->fail( $message, "http", $response, $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::Requests:

    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/

    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

    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

         $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

         $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

         $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.


    The following methods are intended as points for subclasses to
    override, to add extra functionallity.


       $http->prepare_request( $request )

    Called just before the HTTP::Request object is sent to the server.


       $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.


    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

    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

      * 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


       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


 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;


      * - Hypertext Transfer Protocol --


    Parts of this code, or bugfixes to it were paid for by

      * SocialFlow

      * Shadowcat Systems

      * NET-A-PORTER

      * Cisco


    Paul Evans <>