HTTP(3pm)
π HTTP(3pm) β AnyEvent::HTTP π
okay so bestie, welcome to HTTP(3pm), the manual page for AnyEvent::HTTP. It's giving main character energy, and we're keeping every single fact, no cap. β¨
β¨ NAME β¨
AnyEvent::HTTP β simple but non-blocking HTTP/HTTPS client π¦
π SYNOPSIS π
use AnyEvent::HTTP;
http_get "http://www.nethype.de/", sub { print $_[1] };
# ... do something else hereπ DESCRIPTION π
This module is an AnyEvent user, you need to make sure that you use and run a supported event loop. okay so that's the vibe check first.
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. π₯
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. π
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. π«Ά
π¦ METHODS π¦
πΈ http_get $url, key => value..., $cb->($data, $headers) πΈ
Executes an HTTP-GET request. See the http_request function for details on additional parameters and the return value.
πΊ http_head $url, key => value..., $cb->($data, $headers) πΊ
Executes an HTTP-HEAD request. See the http_request function for details on additional parameters and the return value.
πΌ http_post $url, $body, key => value..., $cb->($data, $headers) πΌ
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.
π http_request $method => $url, key => value..., $cb->($data, $headers) π
Executes a HTTP request of type $method (e.g. GET, POST). The URL must be an absolute http or https URL. β¨
When called in void context, nothing is returned. In other contexts, http_request returns a "cancellation guard" - you have to keep the object at least alive until the callback gets called. If the object gets destroyed before the callback is called, the request will be cancelled. β οΈ
The callback will be called with the response body data as first argument (or undef if an error occurred), and a hash-ref with response headers (and trailers) as second argument.
All the headers in that hash are lowercased. In addition to the response headers, the "pseudo-headers" (uppercase to avoid clashing with possible response headers) HTTPVersion, Status and Reason contain the three parts of the HTTP Status-Line of the same name. If an error occurs during the body phase of a request, then the original Status and Reason values from the header are available as OrigStatus and OrigReason. π
The pseudo-header URL contains the actual URL (which can differ from the requested URL when following redirects - for example, you might get an error that your URL scheme is not supported even though your URL is a valid http URL because it redirected to an ftp URL, in which case you can look at the URL pseudo header).
The pseudo-header Redirect only exists when the request was a result of an internal redirect. In that case it is an array reference with the ($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. π
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, $headers->{Status} will be 590-599 and the Reason pseudo-header will contain an error message. Currently the following status codes are used:
595- errors during connection establishment, proxy handshake. π596- errors during TLS negotiation, request sending and header processing. π597- errors during body receiving or processing. π«598- user aborted request viaon_headeroron_body. π599- other, usually nonretryable, errors (garbled URL etc.). π«
A typical callback might look like this:
sub {
my ($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: π«
recurse => $count(default:$MAX_RECURSE) β Whether to recurse requests or not, e.g. on redirects, authentication and other retries and so on, and how often to do so.
Only redirects to http and https URLs are supported. While most common redirection forms are handled entirely within this module, some require the use of the optional URI module. If it is required but missing, then the request will fail with an error.
headers => hashrefβ The request headers to use. Currently,http_requestmay provide its ownHost:,Content-Length:,Connection:andCookie:headers and will provide defaults at least forTE:,Referer:andUser-Agent:(this can be suppressed by usingundeffor these headers in which case they won't be sent at all).
You really should provide your own User-Agent: header value that is appropriate for your program - I wouldn't be surprised if the default AnyEvent string gets blocked by webservers sooner or later.
Also, make sure that your headers names and values do not contain any embedded newlines. β οΈ
timeout => $secondsβ The time-out to use for various stages - each connect attempt will reset the timeout, as will read or write activity, i.e. this is not an overall timeout.
Default timeout is 5 minutes.
proxy => [$host, $port[, $scheme]] or undefβ Use the given http proxy for all requests, or no proxy ifundefis used.
$scheme must be either missing or must be http for HTTP.
If not specified, then the default proxy is used (see AnyEvent::HTTP::set_proxy).
Currently, if your proxy requires authorization, you have to specify an appropriate Proxy-Authorization header in every request.
Note that this module will prefer an existing persistent connection, even if that connection was made using another proxy. If you need to ensure that a new connection is made in this case, you can either force persistent to false or e.g. use the proxy address in your sessionid.
body => $stringβ The request body, usually empty. Will be sent as-is (future versions of this module might offer more options).cookie_jar => $hash_refβ 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 - see the AnyEvent::HTTP::cookie_jar_expire function if you wish to remove expired or session-only cookies, and also for documentation on the format of the cookie jar.
Note that this cookie implementation is not 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 most cookie-using sites working. Cookies are a privacy disaster, do not use them unless required to. π¨
When cookie processing is enabled, the Cookie: and Set-Cookie: headers will be set and handled by this module, otherwise they will be left untouched.
tls_ctx => $scheme | $tls_ctxβ Specifies the AnyEvent::TLS context to be used for https connections. This parameter follows the same rules as thetls_ctxparameter to AnyEvent::Handle, but additionally, the two stringsloworhighcan 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".
See also the sessionid parameter.
sessionid => $stringβ The module might reuse connections to the same host internally (regardless of other settings, such astcp_connectorproxy). Sometimes (e.g. when using TLS or a specfic proxy), you do not want to reuse connections from other sessions. This can be achieved by setting this parameter to some unique ID (such as the address of an object storing your state data or the TLS context, or the proxy IP) - only connections using the same unique ID will be reused. πͺͺon_prepare => $callback->($fh)β In rare cases you need to "tune" the socket before it is used to connect (for example, to bind it on a given IP address). This parameter overrides the prepare callback passed toAnyEvent::Socket::tcp_connectand behaves exactly the same way (e.g. it has to provide a timeout). See the description for the$prepare_cbargument ofAnyEvent::Socket::tcp_connectfor details. π οΈtcp_connect => $callback->($host, $service, $connect_cb, $prepare_cb)β In even rarer cases you want total control over how AnyEvent::HTTP establishes connections. Normally it uses AnyEvent::Socket::tcp_connect to do this, but you can provide your owntcp_connectfunction - obviously, it has to follow the same calling conventions, except that it may always return a connection guard object.
The connections made by this hook will be treated as equivalent to connections made the built-in way, specifically, they will be put into and taken from the persistent connection cache. If your $tcp_connect function is incompatible with this kind of re-use, consider switching off persistent connections and/or providing a sessionid identifier. π
There are probably, like, so many weird uses for this function β from tracing the hosts http_request actually tries to connect to, to (inexact but fast) host => IP address caching, or even socks protocol support. iykyk. π
on_header => $callback->($headers)β when you set this, the callback gets called with the header hash the moment headers have successfully arrived from the remote server (not on locally-generated errors, ok? those don't count).
It has to return either true (and then AnyEvent::HTTP keeps going π), or false, in which case AnyEvent::HTTP cancels the download and calls the finish callback with an error code of 598.
This callback is useful for, among other things, quickly rejecting unwanted content β which, if that content is supposed to be rare, can be faster than first doing a HEAD request.
The downside? Cancelling the request makes it impossible to re-use the connection. also the on_header callback will not receive any trailer (headers sent after the response body). sad but true.
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)β when specified, all body data gets passed to this callback instead of to the completion callback. So the completion callback gets the empty string instead of the body data. bestie, don't be confused by that.
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).
The downside to cancelling the request is that it makes it impossible to re-use the connection.
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 => $enableβ when enabled (default is disabled), the behaviour of AnyEvent::HTTP changes considerably: after parsing the headers, and instead of downloading the body (if any), the completion callback will be called. Instead of the$bodyargument containing the body data, the callback will receive theAnyEvent::Handleobject associated with the connection. In error cases,undefwill be passed. When there is no body (e.g. status304), 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, use chunked transfer encoding etc., and configured in unspecified ways. The user is responsible for this handle (it will not be used by this module anymore). π it's yours now, congratulations.
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.
persistent => $booleanβ try to create/reuse a persistent connection. When this flag is set (default: true for idempotent requests, false for all others), thenhttp_requesttries to re-use an existing (previously-created) persistent connection to same host (i.e. identical URL scheme, hostname, port and sessionid) and, failing that, tries to create a new one.
Requests failing in certain ways will be automatically retried once, which is dangerous for non-idempotent requests, which is why it defaults to off for them. The reason for this is because the bozos who designed HTTP/1.1 made it impossible to distinguish between a fatal error and a normal connection timeout, so you literally never know whether there was a problem with your request or not. π
When reusing an existent connection, many parameters (such as TLS context) will be ignored. See the sessionid parameter for a workaround.
keepalive => $booleanβ only used whenpersistentis also true. This parameter decides whetherhttp_requesttries to handshake a HTTP/1.0-style keep-alive connection (as opposed to only a HTTP/1.1 persistent connection).
The default is true, except when using a proxy, in which case it defaults to false, as HTTP/1.0 proxies cannot support this in a meaningful way.
handle_params => { key => value ... }β the key-value pairs in this hash will be passed to any AnyEvent::Handle constructor that is called β not all requests will create a handle, and sometimes more than one is created, so this parameter is only good for setting hints.
Example: set the maximum read size to 4096, to potentially conserve memory at the cost of speed.
handle_params => {
max_read_size => 4096,
},Example: do a simple HTTP GET request for http://www.nethype.de/ and print the response body.
http_request GET => "http://www.nethype.de/", sub {
my ($body, $hdr) = @_;
print "$body\n";
};Example: do a HTTP HEAD request on https://www.google.com/, use a timeout of 30 seconds.
http_request
HEAD => "https://www.google.com",
headers => { "user-agent" => "MySearchClient 1.0" },
timeout => 30,
sub {
my ($body, $hdr) = @_;
use Data::Dumper;
print Dumper $hdr;
}
;Example: do 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;π¦ DNS CACHING π¦
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. So if you want DNS caching, you currently have to provide your own default resolver (by storing a suitable resolver object in $AnyEvent::DNS::RESOLVER) or your own tcp_connect callback. no default cache for you bestie, you gotta bring your own. π
π GLOBAL FUNCTIONS AND VARIABLES π
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, and it croaks otherwise. π¨
To clear an already-set proxy, use undef.
When AnyEvent::HTTP is loaded for the first time it will query the default proxy from the operating system, currently by looking at $ENV{http_proxy}.
AnyEvent::HTTP::cookie_jar_expire $jar[, $session_end]
Remove all cookies from the cookie jar that have been expired. If $session_end is given and true, then additionally remove all session cookies.
You should call this function (with a true $session_end) before you save cookies to disk, and you should call this function after loading them again. If you have a long-running program you can additionally call this function from time to time. πͺβ¨
A cookie jar is initially an empty hash-reference that is managed by this module. Its format is subject to change, but currently it is as follows:
The key "version" has to contain 2, otherwise the hash gets cleared. All other keys are hostnames or IP addresses pointing to hash-references. The key for these inner hash references is the server path for which this cookie is meant, and the values are again hash-references. Each key of those hash-references is a cookie name, and the value, you guessed it, is another hash-reference β this time with the key-value pairs from the cookie, except for "expires" and "max-age", which have been replaced by a "_expires" key that contains the cookie expiry timestamp. Session cookies are indicated by not having an "_expires" key.
Here is an example of a cookie jar with a single cookie, so you have a chance of understanding the above paragraph:
{
version => 2,
"10.0.0.1" => {
"/" => {
"mythweb_id" => {
_expires => 1293917923,
value => "ooRung9dThee3ooyXooM1Ohm",
},
},
},
}$date = AnyEvent::HTTP::format_date $timestamp
Takes a POSIX timestamp (seconds since the epoch) and formats it as a HTTP Date (RFC 2616). timezone girlie behavior, slay. π°οΈ
$timestamp = AnyEvent::HTTP::parse_date $date
Takes a HTTP Date (RFC 2616) or a Cookie date (netscape cookie spec) or a bunch of minor variations of those, and returns the corresponding POSIX timestamp, or undef if the date cannot be parsed.
$AnyEvent::HTTP::MAX_RECURSE
The default value for the recurse request parameter (default: 10).
$AnyEvent::HTTP::TIMEOUT
The default timeout for connection operations (default: 300).
$AnyEvent::HTTP::USERAGENT
The default value for the User-Agent header (the default is Mozilla/5.0 (compatible; U; AnyEvent-HTTP/$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 additional requests are queued until previous connections are closed. Both persistent and non-persistent connections are counted in this limit.
The default value for this is 4, and it is highly advisable to not increase it much. fr fr, leave it alone.
For comparison: the RFC's recommend 4 non-persistent or 2 persistent connections, older browsers used 2, newer ones (such as firefox 3) typically use 6, and Opera uses 8 because like, they have the fastest browser and give a shit for everybody else on the planet. ππ
$AnyEvent::HTTP::PERSISTENT_TIMEOUTβ bestie, this is how long an idle persistent connection just sits there, vibing, before AnyEvent::HTTP finally goes "okay you're done, bye" and closes it. Default:3. β³$AnyEvent::HTTP::ACTIVEβ the number of active connections. And no, it's not the number of requests running right now π it's the number of currently open and non-idle TCP connections. Which, lowkey, is a genuinely useful number if you're doing load-leveling. π
π SHOWCASE π
Okay so this part is where we get into the more elaborate "real-world" examples and code snippets β the ones that actually ate, fr fr. Pull up a chair, grab a π, let's go.
π¦ HTTP/1.1 FILE DOWNLOAD π¦
Downloading files over HTTP is, like, genuinely tricky? Especially the second something goes wrong and you're sitting there wanting to resume instead of starting over like a clown. π
So here's a function that kicks off a download and resumes one. It uses the last modified time to check whether the file content changed, it plays nice with a whole bunch of HTTP/1.0 servers too, and on older servers it usually just gives up and falls back to a full re-download. No cap.
It calls that completion callback with either undef β which means a nonretryable error happened, sorry bestie β 0 when the download was partial and should be retried, and 1 if it was successful. β¨
use AnyEvent::HTTP;
sub download($$$) {
my ($url, $file, $cb) = @_;
open my $fh, "+<", $file
or die "$file: $!";
my %hdr;
my $ofs = 0;
if (stat $fh and -s _) {
$ofs = -s _;
warn "-s is ", $ofs;
$hdr{"if-unmodified-since"} = AnyEvent::HTTP::format_date +(stat _)[9];
$hdr{"range"} = "bytes=$ofs-";
}
http_get $url,
headers => \%hdr,
on_header => sub {
my ($hdr) = @_;
if ($hdr->{Status} == 200 && $ofs) {
# resume failed
truncate $fh, $ofs = 0;
}
sysseek $fh, $ofs, 0;
1
},
on_body => sub {
my ($data, $hdr) = @_;
if ($hdr->{Status} =~ /^2/) {
length $data == syswrite $fh, $data
or return; # abort on write errors
}
1
},
sub {
my (undef, $hdr) = @_;
my $status = $hdr->{Status};
if (my $time = AnyEvent::HTTP::parse_date $hdr->{"last-modified"}) {
utime $time, $time, $fh;
}
if ($status == 200 || $status == 206 || $status == 416) {
# download ok || resume ok || file already fully downloaded
$cb->(1, $hdr);
} elsif ($status == 412) {
# file has changed while resuming, delete and retry
unlink $file;
$cb->(0, $hdr);
} elsif ($status == 500 or $status == 503 or $status =~ /^59/) {
# retry later
$cb->(0, $hdr);
} else {
$cb->(undef, $hdr);
}
}
;
}
download "http://server/somelargefile", "/tmp/somelargefile", sub {
if ($_[0]) {
print "OK!\n";
} elsif (defined $_[0]) {
print "please retry later\n";
} else {
print "ERROR\n";
}
};𧦠SOCKS PROXIES π§¦
Socks proxies? Not directly supported by AnyEvent::HTTP, bestie, I'm sorry. π You've got options though: compile your perl so it supports socks, or run an external program like socksify (dante) or tsocks so your program uses a socks proxy transparently. Very "let someone else handle it" energy, honestly iconic.
Or, alternatively, for AnyEvent::HTTP only, you can bring your own tcp_connect function that does the proxy handshake itself β here's an example that works with socks4a proxies:
use Errno;
use AnyEvent::Util;
use AnyEvent::Socket;
use AnyEvent::Handle;
# host, port and username of/for your socks4a proxy
my $socks_host = "10.0.0.23";
my $socks_port = 9050;
my $socks_user = "";
sub socks4a_connect {
my ($host, $port, $connect_cb, $prepare_cb) = @_;
my $hdl = new AnyEvent::Handle
connect => [$socks_host, $socks_port],
on_prepare => sub { $prepare_cb->($_[0]{fh}) },
on_error => sub { $connect_cb->() },
;
$hdl->push_write (pack "CCnNZ*Z*", 4, 1, $port, 1, $socks_user, $host);
$hdl->push_read (chunk => 8, sub {
my ($hdl, $chunk) = @_;
my ($status, $port, $ipn) = unpack "xCna4", $chunk;
if ($status == 0x5a) {
$connect_cb->($hdl->{fh}, (format_address $ipn) . ":$port");
} else {
$! = Errno::ENXIO; $connect_cb->();
}
});
$hdl
}Then you use socks4a_connect instead of tcp_connect when you're out here doing http_requests β possibly after you've switched off the other proxy types first:
AnyEvent::HTTP::set_proxy undef; # usually you do not want other proxies
http_get 'http://www.google.com', tcp_connect => \&socks4a_connect, sub {
my ($data, $headers) = @_;
...
};πΈ Tiny note because I love you: that set_proxy undef line is there because usually you do not want other proxies hanging around while you're doing this. Keep it.
π SEE ALSO π
AnyEvent.
<br>
π AUTHOR π
- Marc Lehmann
<schmorp@schmorp.de> http://home.schmorp.de/
And also β with many thanks to ΠΠΌΠΈΡΡΠΈΠΉ Π¨Π°Π»Π°ΡΠΎΠ², who provided countless testcases and bugreports. π«Ά An absolute legend, protecting us all from bugs.
And that's the whole page, bestie!! No crumbs left. π This was perl v5.36.0, dated 2022-10-14, and it's the HTTP(3pm) man page β go forth and slay your HTTP requests. π
β¨
π¦ where this page comes from
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