NAME

Socket::More::Resolver - Loop Agnostic Asynchronous DNS Resolving

SYNOPSIS

Automatic Event Loop Integration and support

use v5.36;

use AnyEvent; # or IO::Async, Mojo::IOLoop

use Socket::More::Resolver; 

getaddrinfo("www.google.com", 0, {},
  sub {
    # got results
    for(@_){
      # do stuff with results
    }
  },
  sub {
    # got an error. Will be numeric error code, convert to stirng
    say gai_strerror $_[0];
  }


# Normal Event loop setup
my $cv=AE::cv;
$cv->recv;

DESCRIPTION

Easy to use asynchronous DNS resolution with automatic integration into supported event loops or polled manually. It is stand alone module with small footprint.

Key features:

• Automatically integrates into supported event loops

  AnyEvent, IO::Async, Mojo::IOLoop are currently supported and automatically detected. Driver for other loops can be easily added. Non blocking polling is also supported.

• Extendable Event Loop Support

  The user can write a 'driver' for other event loops (and put them on CPAN!)

• Utilises your systems getaddrinfo and getnameinfo

  Gives the results you would expect from your system configuration.

• Threadless Self Managed Worker Pool

  The non blocking and asynchronous behaviour is achieved with a fully contained and self managing worker pool, (no threaded Perl required) and optimised for low memory usage and DNS queries.

MOTIVATION

I wanted a simple way of doing asynchronous name/address lookups that works with local mDNS and local system configuration.

LIMITATIONS AND FEATURES TO BE EXPLORED

• Future/Promise API

  Make a version of getaddrinfo/getnameinfo to return Futures/Promises instead of using callbacks, because people like those.

• Internal mDNS Resolver

  The worker pool works very well for fast DNS lookups, however mDNS lookups take up to 5 seconds (by design), when a name is unknown. This can easily saturate the worker pool if you ask multiple 'wrong names' quickly. Due to the local nature of the mDNS, a standalone event based resolver could solve this.. for the future

USAGE

The resolver is designed to work with or without an event loop with as little fuss as possible. Import your event loop first, if using one, then this module:

#use AnyEvnet; #use IO::Async; #use Mojo::IOLoop
use Socket::More::Resolver; 

This will perform automatic loop integration, pool management with default options and export all symbols and automatically start the worker pool, if it hasn't already been started.

There are a few examples for supported event loops in the 'examples' directory of this distribution.

Import Options

Thanks to Export::These managing this modules exports, module options and symbols can be specified at import time with a hash ref in the import list:

use Socket::More::Resolver {options}, symbols ...;

eg
use Socket::More::Resolver {max_workers=>10, prefork=>1}, qw<getaddrinfo>;

There a handful of options which influence the resolver operation. These are specified as hash ref at import:

• max_workers

  max_worker=>number
  

  Sets the maximum number of workers to spawn. The default is 4.

• prefork

  prefork=>bool
  

  Start all workers at launch instead of as needed.

• no_export

  no_export=>1
  

  When set to a true value, prevents the exporting of symbols into the target namespace.

• no_loop

  no_loop=>bool
  

  When set prevents the integration into event loop. Testing use mainly.

• loop_driver

  loop_driver=>string
  loop_driver=>ARRAY
  loop_driver=>CODE
  

  Provides a hook mechanism to add support for other event loops. If a string or array ref are provided, the contents are unshifted to the internal 'search list' of event loop package names.

  If these packages are loaded, then the first one detected will be considered the event loop to use.

  If a code ref is provided, package name search is bypassed and the code ref is used as a callback.

  See the below on writing a driver.

API

The API is focused on asynchronous usage. That means callbacks are used for reporting results and errors.

getaddrinfo

getaddrinfo(host, port, hints, on_results, on_error);

eg

  getaddrinfo 
    "www.google.com",
    80,
    {family=>AF_INET}, 
    sub {
      for(@_){
        # Process results
      }
    },
    sub {
      # Handle error
    }

host is the hostname or numerical address of the host to resolve port is the port of the host to use hints is hash of hints to adjust processing and restrict results Please refer to Socket or Socke::More::Lookup for details on how these values are used.

on_results is callback which is called with the results (list of hash refs) from the query if no error occurred.

on_error is callback which is called with an error code.

The return value represents the number of outstanding requests/messages to be processed. This will always be a > 0 when resolving a host.

However, if called with no arguments, services the request queue and checks for availability of results. When not using an event loop this acts as the polling mechanism:

eq
 getaddrinfo(...);

 while(getaddrinfo){
  # poll here until all requests are processed
 }

getnameinfo

getnameinfo(addr, flags, on_result, on_error)

addr is the addr field from from a socket or a previous getaddrinfo call hints is hash of hints to adjust processing and restrict results Please refer to Socket or Socke::More::Lookup for details on how these values are used.

on_results is a callback which is called with the result from the query (DNS name) if no error occurred.

on_error is callback which is called with an error code.

Supporting other event loops

If you need to add an event loop which isn't directly supported, the easiest way is to look at the code for one of the existing drivers.

TODO: document this more

How it works (High Level)

When the Socket::More::Resolver package is loaded for the first time, it initialises a pool of pipes to be used by workers. The first 'worker', is used as a templates process and is spawned (forked and exec) into the Socket::More::Resolver::Worker.

Lookup requests are sent to remaining workers which are active to process the blocking request to getaddrinfo or getnameinfo.

Process reaping and re-spawning etc is automatic,

COMPARISION TO OTHER MODULES

Net::DNS::Native

Uses Internal C level threads
Returns file handles for each resolution request
Awkward interface for integration into event loops due to the multiple file
handles

IO::Async

Uses Socket module
Purportedly asynchronouse getaddrinfo, but can block on a single slow request

Mojo::IOLoop

Uses Net::DNS::Native

AnyEvent

Implements it's own resolver
Doesn't use system confuration
Doesn't work with .local multicast DNS

AUTHOR

Ruben Westerberg, drclaw@mac.com

REPOSITORTY and BUGS

Please report any bugs via git hub: https://github.com/drclaw1394/perl-socket-more-resolver

COPYRIGHT AND LICENSE

Copyright (C) 2023 by Ruben Westerberg

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

DISCLAIMER OF WARRANTIES

THIS PACKAGE IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.