NAME

Net::Curl::Parallel - perform concurrent HTTP requests using libcurl

SYNOPSIS

  use Net::Curl::Parallel;

  my $fetch = Net::Curl::Parallel->new(
    agent           => 'Net::Curl::Parallel/v0.1',
    slots           => 10,
    max_redirects   => 3,
    connect_timeout => 50,  # ms
    request_timeout => 500, # ms
  );

  # Add requests to be handled concurrently
  my ($req1) = $fetch->add(HTTP::Request->new(...));         # pass an HTTP::Request instance
  my ($req2) = $fetch->add(GET => 'http://www.example.com'); # pass HTTP::Request constructor args
  my ($req3) = $fetch->try(GET => ...);                      # like add() but don't croak on failure

  # Request the... uh, well, requests
  $fetch->perform;

  # Collect individually
  my $res1 = $fetch->collect($req1);
  my $res2 = $fetch->collect($req2);
  my $res3 = $fetch->collect($req3);

  # Collect a few
  my @responses = $fetch->collect($req1, $req2);

  # Or get the whole set
  my @responses = $fetch->collect;

  # Perform a single request
  my $response = Net::Curl::Parallel->fetch(...);

DESCRIPTION

 Stop trying to make fetch happen; it's not going to happen
   <https://www.youtube.com/watch?v=Pubd-spHN-0>
   -- author of superior module, L<ZR::Curl>, fREW "mean-girl" Schmidt

CLASS METHODS

fetch

Performs a single request and returns the response. Accepts the same parameters as "add" or "try" and returns a Net::Curl::Parallel::Response. Internally, this routine uses "try", so failed requests do not die. Instead, check the value of "failed" in Net::Curl::Parallel::Response.

  my $response = Net::Curl::Parallel->fetch(GET => ...);

  if ($response->failed) {
    ...
  } else {
    ...
  }

max_curls_in_pool

Please see the NOTES below about this class method.

METHODS

new

The default values for constructor arguments have been selected as sensible for an interactive web request. Please exercise care when increasing these numbers to ensure web service worker availability as well as to avoid bandwidth saturation and throttling.

agent

User agent string. Defaults to 'Net::Curl::Parallel/v0.1'.

slots

Max number of requests to process simultaneously. Defaults to 10.

max_redirects

Max number of times a remote server may redirect any single request. Defaults to undef (no redirects).

connect_timeout

Max initial connection time in milliseconds. Defaults to 50.

request_timeout

Max total request time in milliseconds. Defaults to 500.

keep_alive

Autmatically set Connection: keep-alive on all HTTP requests. Defaults to true.

If a request already has a Connection: header, that header will be left alone.

verbose

Turn on verbose logging within curl. Defaults to false.

add

Adds any number of HTTP::Request objects to the download set. May also be called with arguments to pass unchanged to the HTTP::Request constructor, in which case all arguments are consumed and a single request is added.

Any request which fails will croak, preventing the servicing of any further requests. Completed requests result in an Net::Curl::Parallel::Response object.

Returns a list of array indexes that identify the location of the responses in the result array returned by "perform". The order of the returned indexes corresponds to the order of requests passed to add as parameters.

  my @ids  = $fetch->add($req1, $req2, $req3);
  my ($id) = $fetch->add(GET => ...);

  # This also works.
  my $id   = $fetch->add(GET => ...);

try

Similar to "add", but a failed request will result in a failed HTTP::Response with an error message rather than croaking.

  $fetch->try(HTTP::Request->new(...));

  my ($response) = $fetch->perform;

  if ($response->failed) {
    handle_errors($response->error);
  } else {
    do_stuff($response);
  }

perform

Performs all requests and returns a list of each response in the order it was added. This method will not return until all requests have completed or an unhandled error is encountered. Returns a list of Net::Curl::Parallel::Response objects corresponding to the index values returned by the "add" and "try" methods.

The behavior of an individual request when an error is encountered (e.g. unable to reach the remote host, timeout, etc.) is determined by whether the request was added by "add" or "try".

NOTE: This means perform() could end prematurely if a request added with "add" throws an exception, even if all the other requests were added with "try".

collect

When called in list context, returns a list of responses corresponding to the list of request ids passed in. If called without arguments, the defaults to all responses.

When called in scalar context, returns a single response corresponding to the request id passed in. If called without arguments, returns an array ref holding all responses.

NOTE: This will not block if the request is not completed with "perform".

NOTES

POSTs and Expect header

If you "add" a POST request, libcurl normally adds a 'Expect: 100-continue' header depending on the body size. This can often result in undesirable behavior, so Net::Curl::Parallel disables that by adding a blank 'Expect:' header by default.

You can set an 'Expect:' header and Net::Curl::Parallel will leave it alone.

Pool of curls

In order to conserve memory, there is a process-global pool of Net::Curl::Easy objects. These are the objects that do the actual HTTP requests. You can access them with $self->curls.

The pool's size defaults to 50. You can set this by calling

  # Or whatever number
  Net::Curl::Parallel->max_curls_in_pool(20);

The pool will be resized the next time "perform" completes.

Note: The pool's max size is ignored while "perform" is running; the max is only enforced at the end of "perform".

CAVEATS

Remember to call perform

  jp    [4:07 PM] ah, helps if you actually `perform` the requests
  jober [4:09 PM] Ah, good caveat. I ought to put that in the docs.
  jp    [4:09 PM] it is in there, just a little hidden

MAINTAINER

Rob Kinyon <rob.kinyon@gmail.com>

SUPPORT

Initial versions written by ZipRecruiter staff (jober and others).

Codebase and support generously provided by ZipRecruiter for opensourcing.

COPYRIGHT & LICENSE

Copyright (C) 2010-onwards by ZipRecruiter

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

cpanm Net::Curl::Parallel

perl -MCPAN -e shell
install Net::Curl::Parallel