NAME

UniEvent::Resolver - performs asynchronous DNS resolution.

SYNOPSIS

my $loop = UniEvent::Loop->new;
my $resolver = new UniEvent::Resolver($loop);

# simplified form and cancellation
my $req = $resolver->resolve('crazypanda.ru', sub {
    my ($addr, $err, $req) = @_;
    say "cancelled" if $err == UE::SystemError::operation_canceled;
});
$req->cancel;

# advanced form
my $req = $resolver->resolve({
    node       => 'crazypanda.ru',
    service    => 'https',
    use_cache  => 1,
    on_resolve => sub {
        my ($addr, $err, $req) = @_;
        return if $err;
        say "resolved as ", $addr->[0]->ip, ":", $addr->[0]->port;
    },
});

# using loop's resolver
$loop->resolver->resolve('crazypanda.ru', sub { ... });

DESCRIPTION

Resolver performs asynchronous DNS resolution, i.e. it maps symbolic names like "crazypanda.ru" into IP addresses like 91.234.119.79.

Under the hood it uses c-ares library for performing resolution.

Normally, you don't need to call resolver methods directly, as methods like connect($host, $port) in UniEvent::Tcp implicitly uses this resolver. However if you need to resolve something by yourself, it is recommended to use per-loop resolver instance accessible via loop's resolver() method. Such usage shares resolver's cache and worker connections across all loop's consumers.

$loop->resolver->resolve(...);

Per-loop resolver is autocreated with default config on first use. If you need your own custom-configured resolver, you need to create resolver instance and use it instead of per-loop resolver. Alternatively, you can change some settings in per-loop resolver.

METHODS

new([$loop = default], [$config = default])

Constructs new resolver instance, binding the supplied $loop to it and using the provided config. The config is a hashref with the following properties:

cache_expiration_time

If a cache entry is older (in seconds) than cache_expiration_time, it will be deleted from cache and the actual resolving will be made, adding a fresh entry into cache.

Default value: 600 seconds.

cache_limit

Maximum size of cached addresses in the resolver cache. All entries in cache will be cleared upon hitting the limit.

If set to zero, requests will not be cached at all.

Default value: 10000 records.

query_timeout

Timeout value for single request resolution, in seconds.

Default value: 5 seconds.

workers

Maximum number of concurrently resolved requests.

Default value: 5.

resolve($hostname, $callback, [$timeout = 5.0])

resolve(\%params)

Initiates asynchronous DNS resolution. In the simple form, just hostname (node) to be resolved, callback and request timeout is expected. In more advanced form, hashref with the following options is expected:

node [required]

The host name to be resolved

timeout

Max time for address resolution, in seconds

service

string with port number or name of the service (see /etc/services) for port mapping.

port

Port number

hints

Address info hints. Use hints function for costruction.

use_cache

If set to false, cache is not used and actual resolving will be made (after which cache will not be updated).

on_resolve

The callback.

The UniEvent::Resolver::Request is returned. It can be used for tracking address resolution or for the request cancellation.

Callback signature is:

my ($addresses, $error, $request) = @_;

Where $addresses is the array of Net::SockAddr.

cache_expiration_time([$value]) {

Get/set cache expiration time in seconds.

cache_limit ([$value])

Get/set cache limit.

cache_size ()

Returns current size of the cache (number of entries).

queue_size ()

Returns the amount of requests, which are waiting to be resolved by workers.

clear_cache ()

Clears cache by force.

reset()

Cancels all resolving and pending requests. Their callbacks will be called with UE::SystemError::operation_canceled error.

FUNCTIONS

hints($family, $socktype, [$protocol = 0], [$flags = 0])

Constructs address info hints for address resolution.

use UniEvent;
use UniEvent::Resolver;

my $hints = UniEvent::Resolver::hints(AF_INET, SOCK_STREAM, PF_INET)

The address info hints is opaque structure without any user visible operations on it. Its sole purpose is to construct hints for the address resolution.

Flags can be:

NUMERICSERV

If this option is set service field will be treated as a numeric value, i.e. instead of "https" it will assume the number "443" (as a string).

CANONNAME

Resolves CNAME records

Check type constant

cpanm UniEvent

perl -MCPAN -e shell
install UniEvent