package Mojo::Redis::Cache; use Mojo::Base -base; use Mojo::JSON; use Protocol::Redis; use Storable (); use Time::HiRes (); use constant OFFLINE => $ENV{MOJO_REDIS_CACHE_OFFLINE}; has connection => sub { OFFLINE ? shift->_offline_connection : shift->redis->_dequeue->protocol(Protocol::Redis->new(api => 1))->encoding(undef); }; has deserialize => sub { \&Storable::thaw }; has default_expire => 600; has namespace => 'cache:mojo:redis'; has refresh => 0; has redis => sub { Carp::confess('redis is required in constructor') }; has serialize => sub { \&Storable::freeze }; sub compute_p { my $compute = pop; my $self = shift; my $key = join ':', $self->namespace, shift; my $expire = shift || $self->default_expire; my $p = $self->refresh ? Mojo::Promise->new->resolve : $self->connection->write_p(GET => $key); return $p->then(sub { my $data = $_[0] ? $self->deserialize->(shift) : undef; return $self->_maybe_compute_p($key, $expire, $compute, $data) if $expire < 0; return $self->_compute_p($key, $expire, $compute) unless $data; return $data->[0]; }); } sub memoize_p { my ($self, $obj, $method) = (shift, shift, shift); my $args = ref $_[0] eq 'ARRAY' ? shift : []; my $expire = shift || $self->default_expire; my $key = join ':', '@M' => (ref($obj) || $obj), $method, Mojo::JSON::encode_json($args); return $self->compute_p($key, $expire, sub { $obj->$method(@$args) }); } sub _compute_p { my ($self, $key, $expire, $compute) = @_; my $set = sub { my $data = shift; my @set = $expire < 0 ? $self->serialize->([$data, _time() + -$expire]) : ($self->serialize->([$data]), PX => 1000 * $expire); $self->connection->write_p(SET => $key => @set)->then(sub {$data}); }; my $data = $compute->(); return UNIVERSAL::can($data, 'then') ? $data->then(sub { $set->(@_) }) : $set->($data); } sub _maybe_compute_p { my ($self, $key, $expire, $compute, $data) = @_; # Nothing in cache return $self->_compute_p($key => $expire, $compute)->then(sub { ($_[0], {computed => 1}) }) unless $data; # No need to refresh cache return ($data->[0], {expired => 0}) if $data->[1] and _time() < $data->[1]; # Try to refresh, but use old data on error my $p = Mojo::Promise->new; eval { $self->_compute_p($key => $expire, $compute)->then( sub { $p->resolve(shift, {computed => 1, expired => 1}) }, sub { $p->resolve($data->[0], {error => $_[0], expired => 1}) }, ); } or do { $p->resolve($data->[0], {error => $@, expired => 1}); }; return $p; } sub _offline_connection { state $c = eval <<'HERE' or die $@; package Mojo::Redis::Connection::Offline; use Mojo::Base 'Mojo::Redis::Connection'; our $STORE = {}; # Meant for internal use only sub write_p { my ($conn, $op, $key) = (shift, shift, shift); if ($op eq 'SET') { $STORE->{$conn->url}{$key} = [$_[0], defined $_[2] ? $_[2] + Mojo::Redis::Cache::_time() * 1000 : undef]; return Mojo::Promise->new->resolve('OK'); } else { my $val = $STORE->{$conn->url}{$key} || []; my $expired = $val->[1] && $val->[1] < Mojo::Redis::Cache::_time() * 1000; delete $STORE->{$conn->url}{$key} if $expired; return Mojo::Promise->new->resolve($expired ? undef : $val->[0]); } } 'Mojo::Redis::Connection::Offline'; HERE my $redis = shift->redis; return $c->new(protocol => $redis->protocol_class->new(api => 1), url => $redis->url); } sub _time { Time::HiRes::time() } 1; =encoding utf8 =head1 NAME Mojo::Redis::Cache - Simple cache interface using Redis =head1 SYNOPSIS use Mojo::Redis; my $redis = Mojo::Redis->new; my $cache = $redis->cache; # Cache and expire the data after 60.7 seconds $cache->compute_p("some:key", 60.7, sub { my $p = Mojo::Promise->new; Mojo::IOLoop->timer(0.1 => sub { $p->resolve("some data") }); return $p; })->then(sub { my $some_key = shift; }); # Cache and expire the data after default_expire() seconds $cache->compute_p("some:key", sub { return {some => "data"}; })->then(sub { my $some_key = shift; }); # Call $obj->get_some_slow_data() and cache the return value $cache->memoize_p($obj, "get_some_slow_data")->then(sub { my $data = shift; }); # Call $obj->get_some_data_by_id({id => 42}) and cache the return value $cache->memoize_p($obj, "get_some_data_by_id", [{id => 42}])->then(sub { my $data = shift; }); See L<https://github.com/jhthorsen/mojo-redis/blob/master/examples/cache.pl> for example L<Mojolicious> application. =head1 DESCRIPTION L<Mojo::Redis::Cache> provides a simple interface for caching data in the Redis database. There is no "check if exists", "get" or "set" methods in this class. Instead, both L</compute_p> and L</memoize_p> will fetch the value from Redis, if the given compute function / method has been called once, and the cached data is not expired. If you need to check if the value exists, then you can manually look up the the key using L<Mojo::Redis::Database/exists>. =head1 ENVIRONMENT VARIABLES =head2 MOJO_REDIS_CACHE_OFFLINE Set C<MOJO_REDIS_CACHE_OFFLINE> to 1 if you want to use this cache without a real Redis backend. This can be useful in unit tests. =head1 ATTRIBUTES =head2 connection $conn = $self->connection; $self = $self->connection(Mojo::Redis::Connection->new); Holds a L<Mojo::Redis::Connection> object. =head2 default_expire $num = $self->default_expire; $self = $self->default_expire(600); Holds the default expire time for cached data. =head2 deserialize $cb = $self->deserialize; $self = $self->deserialize(\&Mojo::JSON::decode_json); Holds a callback used to deserialize data from Redis. =head2 namespace $str = $self->namespace; $self = $self->namespace("cache:mojo:redis"); Prefix for the cache key. =head2 redis $conn = $self->redis; $self = $self->redis(Mojo::Redis->new); Holds a L<Mojo::Redis> object used to create the connection to talk with Redis. =head2 refresh $bool = $self->refresh; $self = $self->refresh(1); Will force the cache to be computed again if set to a true value. =head2 serialize $cb = $self->serialize; $self = $self->serialize(\&Mojo::JSON::encode_json); Holds a callback used to serialize before storing the data in Redis. =head1 METHODS =head2 compute_p $promise = $self->compute_p($key => $expire => $compute_function); $promise = $self->compute_p($key => $expire => sub { return "data" }); $promise = $self->compute_p($key => $expire => sub { return Mojo::Promise->new }); This method will store the return value from the C<$compute_function> the first time it is called and pass the same value to L<Mojo::Promise/then>. C<$compute_function> will not be called the next time, if the C<$key> is still present in Redis, but instead the cached value will be passed on to L<Mojo::Promise/then>. C<$key> will be prefixed by L</namespace> resulting in "namespace:some-key". C<$expire> is the number of seconds before the cache should expire, and will default to L</default_expire> unless passed in. The last argument is a callback used to calculate cached value. C<$expire> can also be a negative number. This will result in serving old cache in the case where the C<$compute_function> fails. An example usecase would be if you are fetching Twitter updates for your website, but instead of throwing an exception if Twitter is down, you will serve old data instead. Note that the fulfilled promise will get two variables passed in: $promise->then(sub { my ($data, $info) = @_ }); C<$info> is a hash and can have these keys: =over 2 =item * computed Will be true if the C<$compute_function> was called successfully and C<$data> is fresh. =item * expired Will be true if C<$data> is expired. If this key is present and false, it will indicate that the C<$data> is within the expiration period. The C<expired> key can be found together with both L</computed> and L</error>. =item * error Will hold a string if the C<$compute_function> failed. =back Negative C<$expire> is currently EXPERIMENTAL, but unlikely to go away. =head2 memoize_p $promise = $self->memoize_p($obj, $method_name, \@args, $expire); $promise = $self->memoize_p($class, $method_name, \@args, $expire); L</memoize_p> behaves the same way as L</compute_p>, but has a convenient interface for calling methods on an object. One of the benefits is that you do not have to come up with your own cache key. This method is pretty much the same as: $promise = $self->compute_p( join(":", $self->namespace, "@M", ref($obj), $method_name, serialize(\@args)), $expire, sub { return $obj->$method_name(@args) } ); See L</compute_p> regarding C<$expire>. =head1 SEE ALSO L<Mojo::Redis> =cut