[ViewVC] Annotation of: cvs/AnyEvent-HTTP/README

NAME
    AnyEvent::HTTP - simple but non-blocking HTTP/HTTPS client

SYNOPSIS
       use AnyEvent::HTTP;

       http_get "http://www.nethype.de/", sub { print $_[1] };

       # ... do something else here

DESCRIPTION
    This module is an AnyEvent user, you need to make sure that you use and
    run a supported event loop.

    This module implements a simple, stateless and non-blocking HTTP client.
    It supports GET, POST and other request methods, cookies and more, all
    on a very low level. It can follow redirects supports proxies and
    automatically limits the number of connections to the values specified
    in the RFC.

    It should generally be a "good client" that is enough for most HTTP
    tasks. Simple tasks should be simple, but complex tasks should still be
    possible as the user retains control over request and response headers.

    The caller is responsible for authentication management, cookies (if the
    simplistic implementation in this module doesn't suffice), referer and
    other high-level protocol details for which this module offers only
    limited support.

  METHODS
    http_get $url, key => value..., $cb->($data, $headers)
        Executes an HTTP-GET request. See the http_request function for
        details on additional parameters and the return value.

    http_head $url, key => value..., $cb->($data, $headers)
        Executes an HTTP-HEAD request. See the http_request function for
        details on additional parameters and the return value.

    http_post $url, $body, key => value..., $cb->($data, $headers)
        Executes an HTTP-POST request with a request body of $body. See the
        http_request function for details on additional parameters and the
        return value.

    http_request $method => $url, key => value..., $cb->($data, $headers)
        Executes a HTTP request of type $method (e.g. "GET", "POST"). The
        URL must be an absolute http or https URL.

        When called in void context, nothing is returned. In other contexts,
        "http_request" returns a "cancellation guard" - you have to keep the
        object at least alive until the callback get called. If the object
        gets destroyed before the callbakc is called, the request will be
        cancelled.

        The callback will be called with the response body data as first
        argument (or "undef" if an error occured), and a hash-ref with
        response headers as second argument.

        All the headers in that hash are lowercased. In addition to the
        response headers, the "pseudo-headers" (uppercase to avoid clashing
        with possible response headers) "HTTPVersion", "Status" and "Reason"
        contain the three parts of the HTTP Status-Line of the same name.

        The pseudo-header "URL" contains the actual URL (which can differ
        from the requested URL when following redirects - for example, you
        might get an error that your URL scheme is not supported even though
        your URL is a valid http URL because it redirected to an ftp URL, in
        which case you can look at the URL pseudo header).

        The pseudo-header "Redirect" only exists when the request was a
        result of an internal redirect. In that case it is an array
        reference with the "($data, $headers)" from the redirect response.
        Note that this response could in turn be the result of a redirect
        itself, and "$headers->{Redirect}[1]{Redirect}" will then contain
        the original response, and so on.

        If the server sends a header multiple times, then their contents
        will be joined together with a comma (","), as per the HTTP spec.

        If an internal error occurs, such as not being able to resolve a
        hostname, then $data will be "undef", "$headers->{Status}" will be
        "59x" (usually 599) and the "Reason" pseudo-header will contain an
        error message.

        A typical callback might look like this:

           sub {
              my ($body, $hdr) = @_;

              if ($hdr->{Status} =~ /^2/) {
                 ... everything should be ok
              } else {
                 print "error, $hdr->{Status} $hdr->{Reason}\n";
              }
           }

        Additional parameters are key-value pairs, and are fully optional.
        They include:

        recurse => $count (default: $MAX_RECURSE)
            Whether to recurse requests or not, e.g. on redirects,
            authentication retries and so on, and how often to do so.

        headers => hashref
            The request headers to use. Currently, "http_request" may
            provide its own "Host:", "Content-Length:", "Connection:" and
            "Cookie:" headers and will provide defaults for "User-Agent:"
            and "Referer:" (this can be suppressed by using "undef" for
            these headers in which case they won't be sent at all).

        timeout => $seconds
            The time-out to use for various stages - each connect attempt
            will reset the timeout, as will read or write activity, i.e.
            this is not an overall timeout.

            Default timeout is 5 minutes.

        proxy => [$host, $port[, $scheme]] or undef
            Use the given http proxy for all requests. If not specified,
            then the default proxy (as specified by $ENV{http_proxy}) is
            used.

            $scheme must be either missing, "http" for HTTP or "https" for
            HTTPS.

        body => $string
            The request body, usually empty. Will be-sent as-is (future
            versions of this module might offer more options).

        cookie_jar => $hash_ref
            Passing this parameter enables (simplified) cookie-processing,
            loosely based on the original netscape specification.

            The $hash_ref must be an (initially empty) hash reference which
            will get updated automatically. It is possible to save the
            cookie_jar to persistent storage with something like JSON or
            Storable, but this is not recommended, as expiry times are
            currently being ignored.

            Note that this cookie implementation is not of very high
            quality, nor meant to be complete. If you want complete cookie
            management you have to do that on your own. "cookie_jar" is
            meant as a quick fix to get some cookie-using sites working.
            Cookies are a privacy disaster, do not use them unless required
            to.

        tls_ctx => $scheme | $tls_ctx
            Specifies the AnyEvent::TLS context to be used for https
            connections. This parameter follows the same rules as the
            "tls_ctx" parameter to AnyEvent::Handle, but additionally, the
            two strings "low" or "high" can be specified, which give you a
            predefined low-security (no verification, highest compatibility)
            and high-security (CA and common-name verification) TLS context.

            The default for this option is "low", which could be interpreted
            as "give me the page, no matter what".

        on_prepare => $callback->($fh)
            In rare cases you need to "tune" the socket before it is used to
            connect (for exmaple, to bind it on a given IP address). This
            parameter overrides the prepare callback passed to
            "AnyEvent::Socket::tcp_connect" and behaves exactly the same way
            (e.g. it has to provide a timeout). See the description for the
            $prepare_cb argument of "AnyEvent::Socket::tcp_connect" for
            details.

        on_header => $callback->($headers)
            When specified, this callback will be called with the header
            hash as soon as headers have been successfully received from the
            remote server (not on locally-generated errors).

            It has to return either true (in which case AnyEvent::HTTP will
            continue), or false, in which case AnyEvent::HTTP will cancel
            the download (and call the finish callback with an error code of
            598).

            This callback is useful, among other things, to quickly reject
            unwanted content, which, if it is supposed to be rare, can be
            faster than first doing a "HEAD" request.

            Example: cancel the request unless the content-type is
            "text/html".

               on_header => sub {
                  $_[0]{"content-type"} =~ /^text\/html\s*(?:;|$)/
               },

        on_body => $callback->($partial_body, $headers)
            When specified, all body data will be passed to this callback
            instead of to the completion callback. The completion callback
            will get the empty string instead of the body data.

            It has to return either true (in which case AnyEvent::HTTP will
            continue), or false, in which case AnyEvent::HTTP will cancel
            the download (and call the completion callback with an error
            code of 598).

            This callback is useful when the data is too large to be held in
            memory (so the callback writes it to a file) or when only some
            information should be extracted, or when the body should be
            processed incrementally.

            It is usually preferred over doing your own body handling via
            "want_body_handle", but in case of streaming APIs, where HTTP is
            only used to create a connection, "want_body_handle" is the
            better alternative, as it allows you to install your own event
            handler, reducing resource usage.

        want_body_handle => $enable
            When enabled (default is disabled), the behaviour of
            AnyEvent::HTTP changes considerably: after parsing the headers,
            and instead of downloading the body (if any), the completion
            callback will be called. Instead of the $body argument
            containing the body data, the callback will receive the
            AnyEvent::Handle object associated with the connection. In error
            cases, "undef" will be passed. When there is no body (e.g.
            status 304), the empty string will be passed.

            The handle object might or might not be in TLS mode, might be
            connected to a proxy, be a persistent connection etc., and
            configured in unspecified ways. The user is responsible for this
            handle (it will not be used by this module anymore).

            This is useful with some push-type services, where, after the
            initial headers, an interactive protocol is used (typical
            example would be the push-style twitter API which starts a
            JSON/XML stream).

            If you think you need this, first have a look at "on_body", to
            see if that doesn't solve your problem in a better way.

        Example: make a simple HTTP GET request for http://www.nethype.de/

           http_request GET => "http://www.nethype.de/", sub {
              my ($body, $hdr) = @_;
              print "$body\n";
           };

        Example: make a HTTP HEAD request on https://www.google.com/, use a
        timeout of 30 seconds.

           http_request
              GET     => "https://www.google.com",
              timeout => 30,
              sub {
                 my ($body, $hdr) = @_;
                 use Data::Dumper;
                 print Dumper $hdr;
              }
           ;

        Example: make another simple HTTP GET request, but immediately try
        to cancel it.

           my $request = http_request GET => "http://www.nethype.de/", sub {
              my ($body, $hdr) = @_;
              print "$body\n";
           };

           undef $request;

  DNS CACHING
    AnyEvent::HTTP uses the AnyEvent::Socket::tcp_connect function for the
    actual connection, which in turn uses AnyEvent::DNS to resolve
    hostnames. The latter is a simple stub resolver and does no caching on
    its own. If you want DNS caching, you currently have to provide your own
    default resolver (by storing a suitable resolver object in
    $AnyEvent::DNS::RESOLVER).

  GLOBAL FUNCTIONS AND VARIABLES
    AnyEvent::HTTP::set_proxy "proxy-url"
        Sets the default proxy server to use. The proxy-url must begin with
        a string of the form "http://host:port" (optionally "https:..."),
        croaks otherwise.

        To clear an already-set proxy, use "undef".

    $AnyEvent::HTTP::MAX_RECURSE
        The default value for the "recurse" request parameter (default: 10).

    $AnyEvent::HTTP::USERAGENT
        The default value for the "User-Agent" header (the default is
        "Mozilla/5.0 (compatible; U; AnyEvent-HTTP/$VERSION;
        +http://software.schmorp.de/pkg/AnyEvent)").

    $AnyEvent::HTTP::MAX_PER_HOST
        The maximum number of concurrent connections to the same host
        (identified by the hostname). If the limit is exceeded, then the
        additional requests are queued until previous connections are
        closed.

        The default value for this is 4, and it is highly advisable to not
        increase it.

    $AnyEvent::HTTP::ACTIVE
        The number of active connections. This is not the number of
        currently running requests, but the number of currently open and
        non-idle TCP connections. This number of can be useful for
        load-leveling.

SEE ALSO
    AnyEvent.

AUTHOR
       Marc Lehmann <schmorp@schmorp.de>
       http://home.schmorp.de/

    With many thanks to Дмитрий Шалашов, who provided
    countless testcases and bugreports.

Revision:	1.13
Committed:	Wed Jun 16 19:17:30 2010 UTC (13 years, 11 months ago) by root
Branch:	MAIN
CVS Tags:	rel-1_46, rel-1_45
Changes since 1.12:	+24 -4 lines
Log Message:	1.45
#	User	Rev	Content
1	root	1.1	NAME
2	root	1.2	AnyEvent::HTTP - simple but non-blocking HTTP/HTTPS client
3	root	1.1
4			SYNOPSIS
5	root	1.2	use AnyEvent::HTTP;
6	root	1.1
7	root	1.3	http_get "http://www.nethype.de/", sub { print $_[1] };
8
9			# ... do something else here
10
11	root	1.1	DESCRIPTION
12			This module is an AnyEvent user, you need to make sure that you use and
13			run a supported event loop.
14
15	root	1.2	This module implements a simple, stateless and non-blocking HTTP client.
16			It supports GET, POST and other request methods, cookies and more, all
17			on a very low level. It can follow redirects supports proxies and
18			automatically limits the number of connections to the values specified
19			in the RFC.
20
21			It should generally be a "good client" that is enough for most HTTP
22			tasks. Simple tasks should be simple, but complex tasks should still be
23			possible as the user retains control over request and response headers.
24
25			The caller is responsible for authentication management, cookies (if the
26			simplistic implementation in this module doesn't suffice), referer and
27			other high-level protocol details for which this module offers only
28			limited support.
29
30			METHODS
31			http_get $url, key => value..., $cb->($data, $headers)
32			Executes an HTTP-GET request. See the http_request function for
33	root	1.5	details on additional parameters and the return value.
34	root	1.2
35			http_head $url, key => value..., $cb->($data, $headers)
36			Executes an HTTP-HEAD request. See the http_request function for
37	root	1.5	details on additional parameters and the return value.
38	root	1.2
39			http_post $url, $body, key => value..., $cb->($data, $headers)
40	root	1.4	Executes an HTTP-POST request with a request body of $body. See the
41	root	1.5	http_request function for details on additional parameters and the
42			return value.
43	root	1.2
44			http_request $method => $url, key => value..., $cb->($data, $headers)
45			Executes a HTTP request of type $method (e.g. "GET", "POST"). The
46			URL must be an absolute http or https URL.
47
48	root	1.5	When called in void context, nothing is returned. In other contexts,
49			"http_request" returns a "cancellation guard" - you have to keep the
50			object at least alive until the callback get called. If the object
51			gets destroyed before the callbakc is called, the request will be
52			cancelled.
53
54	root	1.8	The callback will be called with the response body data as first
55			argument (or "undef" if an error occured), and a hash-ref with
56			response headers as second argument.
57	root	1.2
58			All the headers in that hash are lowercased. In addition to the
59	root	1.13	response headers, the "pseudo-headers" (uppercase to avoid clashing
60			with possible response headers) "HTTPVersion", "Status" and "Reason"
61			contain the three parts of the HTTP Status-Line of the same name.
62
63			The pseudo-header "URL" contains the actual URL (which can differ
64			from the requested URL when following redirects - for example, you
65			might get an error that your URL scheme is not supported even though
66			your URL is a valid http URL because it redirected to an ftp URL, in
67			which case you can look at the URL pseudo header).
68
69			The pseudo-header "Redirect" only exists when the request was a
70			result of an internal redirect. In that case it is an array
71			reference with the "($data, $headers)" from the redirect response.
72			Note that this response could in turn be the result of a redirect
73			itself, and "$headers->{Redirect}[1]{Redirect}" will then contain
74			the original response, and so on.
75	root	1.3
76	root	1.6	If the server sends a header multiple times, then their contents
77			will be joined together with a comma (","), as per the HTTP spec.
78	root	1.2
79			If an internal error occurs, such as not being able to resolve a
80			hostname, then $data will be "undef", "$headers->{Status}" will be
81	root	1.8	"59x" (usually 599) and the "Reason" pseudo-header will contain an
82			error message.
83	root	1.2
84			A typical callback might look like this:
85
86			sub {
87			my ($body, $hdr) = @_;
88
89			if ($hdr->{Status} =~ /^2/) {
90			... everything should be ok
91			} else {
92			print "error, $hdr->{Status} $hdr->{Reason}\n";
93			}
94			}
95
96			Additional parameters are key-value pairs, and are fully optional.
97			They include:
98
99			recurse => $count (default: $MAX_RECURSE)
100			Whether to recurse requests or not, e.g. on redirects,
101			authentication retries and so on, and how often to do so.
102
103			headers => hashref
104			The request headers to use. Currently, "http_request" may
105			provide its own "Host:", "Content-Length:", "Connection:" and
106			"Cookie:" headers and will provide defaults for "User-Agent:"
107	root	1.10	and "Referer:" (this can be suppressed by using "undef" for
108			these headers in which case they won't be sent at all).
109	root	1.2
110			timeout => $seconds
111			The time-out to use for various stages - each connect attempt
112	root	1.11	will reset the timeout, as will read or write activity, i.e.
113			this is not an overall timeout.
114
115			Default timeout is 5 minutes.
116	root	1.2
117			proxy => [$host, $port[, $scheme]] or undef
118			Use the given http proxy for all requests. If not specified,
119			then the default proxy (as specified by $ENV{http_proxy}) is
120			used.
121
122	root	1.10	$scheme must be either missing, "http" for HTTP or "https" for
123			HTTPS.
124	root	1.2
125			body => $string
126			The request body, usually empty. Will be-sent as-is (future
127			versions of this module might offer more options).
128
129			cookie_jar => $hash_ref
130			Passing this parameter enables (simplified) cookie-processing,
131			loosely based on the original netscape specification.
132
133			The $hash_ref must be an (initially empty) hash reference which
134			will get updated automatically. It is possible to save the
135			cookie_jar to persistent storage with something like JSON or
136	root	1.8	Storable, but this is not recommended, as expiry times are
137	root	1.2	currently being ignored.
138
139			Note that this cookie implementation is not of very high
140			quality, nor meant to be complete. If you want complete cookie
141			management you have to do that on your own. "cookie_jar" is
142			meant as a quick fix to get some cookie-using sites working.
143			Cookies are a privacy disaster, do not use them unless required
144			to.
145
146	root	1.8	tls_ctx => $scheme \| $tls_ctx
147			Specifies the AnyEvent::TLS context to be used for https
148			connections. This parameter follows the same rules as the
149			"tls_ctx" parameter to AnyEvent::Handle, but additionally, the
150			two strings "low" or "high" can be specified, which give you a
151			predefined low-security (no verification, highest compatibility)
152			and high-security (CA and common-name verification) TLS context.
153
154			The default for this option is "low", which could be interpreted
155			as "give me the page, no matter what".
156
157	root	1.11	on_prepare => $callback->($fh)
158			In rare cases you need to "tune" the socket before it is used to
159			connect (for exmaple, to bind it on a given IP address). This
160			parameter overrides the prepare callback passed to
161			"AnyEvent::Socket::tcp_connect" and behaves exactly the same way
162			(e.g. it has to provide a timeout). See the description for the
163			$prepare_cb argument of "AnyEvent::Socket::tcp_connect" for
164			details.
165
166	root	1.8	on_header => $callback->($headers)
167			When specified, this callback will be called with the header
168			hash as soon as headers have been successfully received from the
169			remote server (not on locally-generated errors).
170
171			It has to return either true (in which case AnyEvent::HTTP will
172			continue), or false, in which case AnyEvent::HTTP will cancel
173			the download (and call the finish callback with an error code of
174			598).
175
176			This callback is useful, among other things, to quickly reject
177			unwanted content, which, if it is supposed to be rare, can be
178			faster than first doing a "HEAD" request.
179
180			Example: cancel the request unless the content-type is
181			"text/html".
182
183			on_header => sub {
184			$_[0]{"content-type"} =~ /^text\/html\s*(?:;\|$)/
185			},
186
187			on_body => $callback->($partial_body, $headers)
188			When specified, all body data will be passed to this callback
189			instead of to the completion callback. The completion callback
190			will get the empty string instead of the body data.
191
192			It has to return either true (in which case AnyEvent::HTTP will
193			continue), or false, in which case AnyEvent::HTTP will cancel
194			the download (and call the completion callback with an error
195			code of 598).
196
197			This callback is useful when the data is too large to be held in
198			memory (so the callback writes it to a file) or when only some
199			information should be extracted, or when the body should be
200			processed incrementally.
201
202			It is usually preferred over doing your own body handling via
203	root	1.9	"want_body_handle", but in case of streaming APIs, where HTTP is
204			only used to create a connection, "want_body_handle" is the
205			better alternative, as it allows you to install your own event
206			handler, reducing resource usage.
207	root	1.8
208			want_body_handle => $enable
209			When enabled (default is disabled), the behaviour of
210			AnyEvent::HTTP changes considerably: after parsing the headers,
211			and instead of downloading the body (if any), the completion
212			callback will be called. Instead of the $body argument
213			containing the body data, the callback will receive the
214			AnyEvent::Handle object associated with the connection. In error
215			cases, "undef" will be passed. When there is no body (e.g.
216			status 304), the empty string will be passed.
217
218			The handle object might or might not be in TLS mode, might be
219			connected to a proxy, be a persistent connection etc., and
220			configured in unspecified ways. The user is responsible for this
221			handle (it will not be used by this module anymore).
222
223			This is useful with some push-type services, where, after the
224			initial headers, an interactive protocol is used (typical
225			example would be the push-style twitter API which starts a
226			JSON/XML stream).
227
228			If you think you need this, first have a look at "on_body", to
229	root	1.9	see if that doesn't solve your problem in a better way.
230	root	1.8
231	root	1.2	Example: make a simple HTTP GET request for http://www.nethype.de/
232
233			http_request GET => "http://www.nethype.de/", sub {
234			my ($body, $hdr) = @_;
235			print "$body\n";
236			};
237
238			Example: make a HTTP HEAD request on https://www.google.com/, use a
239			timeout of 30 seconds.
240
241			http_request
242			GET => "https://www.google.com",
243			timeout => 30,
244			sub {
245			my ($body, $hdr) = @_;
246			use Data::Dumper;
247			print Dumper $hdr;
248			}
249			;
250
251	root	1.5	Example: make another simple HTTP GET request, but immediately try
252			to cancel it.
253
254			my $request = http_request GET => "http://www.nethype.de/", sub {
255			my ($body, $hdr) = @_;
256			print "$body\n";
257			};
258
259			undef $request;
260
261	root	1.13	DNS CACHING
262			AnyEvent::HTTP uses the AnyEvent::Socket::tcp_connect function for the
263			actual connection, which in turn uses AnyEvent::DNS to resolve
264			hostnames. The latter is a simple stub resolver and does no caching on
265			its own. If you want DNS caching, you currently have to provide your own
266			default resolver (by storing a suitable resolver object in
267			$AnyEvent::DNS::RESOLVER).
268
269	root	1.2	GLOBAL FUNCTIONS AND VARIABLES
270			AnyEvent::HTTP::set_proxy "proxy-url"
271			Sets the default proxy server to use. The proxy-url must begin with
272	root	1.12	a string of the form "http://host:port" (optionally "https:..."),
273			croaks otherwise.
274
275			To clear an already-set proxy, use "undef".
276	root	1.2
277			$AnyEvent::HTTP::MAX_RECURSE
278			The default value for the "recurse" request parameter (default: 10).
279
280			$AnyEvent::HTTP::USERAGENT
281			The default value for the "User-Agent" header (the default is
282	root	1.8	"Mozilla/5.0 (compatible; U; AnyEvent-HTTP/$VERSION;
283	root	1.2	+http://software.schmorp.de/pkg/AnyEvent)").
284
285	root	1.8	$AnyEvent::HTTP::MAX_PER_HOST
286	root	1.10	The maximum number of concurrent connections to the same host
287	root	1.8	(identified by the hostname). If the limit is exceeded, then the
288			additional requests are queued until previous connections are
289			closed.
290	root	1.2
291	root	1.8	The default value for this is 4, and it is highly advisable to not
292			increase it.
293	root	1.2
294			$AnyEvent::HTTP::ACTIVE
295			The number of active connections. This is not the number of
296			currently running requests, but the number of currently open and
297			non-idle TCP connections. This number of can be useful for
298			load-leveling.
299	root	1.1
300			SEE ALSO
301	root	1.2	AnyEvent.
302	root	1.1
303			AUTHOR
304	root	1.3	Marc Lehmann <schmorp@schmorp.de>
305			http://home.schmorp.de/
306	root	1.1
307	root	1.7	With many thanks to Дмитрий Шалашов, who provided
308			countless testcases and bugreports.
309