Add support for multiple download attempts for assets that need to be fetched

This will be disabled by default, and can be enabled with
`$app->asset->store->retries(5)`.

Author: kraih

lib/Mojolicious/Plugin/AssetPack/Store.pm

@@ -8,6 +8,7 @@ use Mojo::URL;
 use Mojolicious::Types;
 use Mojolicious::Plugin::AssetPack::Asset;
 use Mojolicious::Plugin::AssetPack::Util qw(diag checksum has_ro DEBUG);
+use Time::HiRes                          qw(sleep);
 
 use constant CACHE_DIR => 'cache';
 
@@ -26,6 +27,8 @@ has asset_class        => 'Mojolicious::Plugin::AssetPack::Asset';
 has default_headers    => sub { +{"Cache-Control" => "max-age=31536000"} };
 has fallback_headers   => sub { +{"Cache-Control" => "max-age=60"} };
 has fallback_templates => sub { +{%FALLBACK_TEMPLATES} };
+has retry_delay        => 3;
+has retries            => 0;
 
 has _types => sub {
   my $t = Mojolicious::Types->new;
@@ -257,14 +260,22 @@ sub _download {
 
   return $asset if $attrs{url}->host ne 'local' and $asset = $self->_already_downloaded($url);
 
-  my $tx = $self->ua->get($url);
-  my $h  = $tx->res->headers;
+  my $tx;
+  my $retries = $self->retries;
+  while (1) {
+    $tx = $self->ua->get($url);
+    last unless my $err = $tx->error;
+
+    if ($retries-- > 0) {
+      sleep $self->retry_delay;
+      next;
+    }
 
-  if (my $err = $tx->error) {
     $self->_log->warn("[AssetPack] Unable to download $url: $err->{message}");
     return undef;
   }
 
+  my $h  = $tx->res->headers;
   my $ct = $h->content_type || '';
   if ($ct ne 'text/plain') {
     $ct =~ s!;.*$!!;
@@ -388,6 +399,20 @@ This is currently an EXPERIMENTAL feature.
 
 See L<Mojolicious::Static/paths> for details.
 
+=head2 retry_delay
+
+  my $delay = $self->retry_delay;
+  $self     = $self->retry_delay(0.5);
+
+Delay in seconds between download attempts for assets that need to be fetched, defaults to C<3>.
+
+=head2 retries
+
+  my $retries = $self->retries;
+  $self       = $self->retries(5);
+
+Number of times asset downloads will be attempted for assets that need to be fetched, defaults to C<0>.
+
 =head2 ua
 
   $ua = $self->ua;

t/fetch-retry.t

@@ -0,0 +1,47 @@
+use lib '.';
+use t::Helper;
+
+use Mojo::IOLoop;
+use Mojo::Server::Daemon;
+use Mojolicious;
+
+my $t = t::Helper->t(pipes => [qw(Css Fetch)]);
+
+my $app = Mojolicious->new;
+$app->config->{attempts} = 0;
+$app->routes->get(
+  '/test.css' => sub {
+    my $c = shift;
+    return $c->render(data => 'Internal server error', status => 500) if $c->app->config->{attempts}++ <= 2;
+    $c->render(data => 'body { color: #00f }');
+  }
+);
+my $responses = [];
+$app->hook(
+  before_dispatch => sub {
+    shift->on(finish => sub { push @$responses, shift->res->code });
+  }
+);
+my $daemon = Mojo::Server::Daemon->new(listen => ['http://*'], ioloop => $t->app->asset->ua->ioloop, app => $app);
+my $port   = $daemon->start->ports->[0];
+
+subtest 'Defaults' => sub {
+  is $t->app->asset->store->retries,     0, 'no retries by default';
+  is $t->app->asset->store->retry_delay, 3, '3 second retry delay by default';
+};
+
+subtest 'Download asset with multiple attempts' => sub {
+  $t->app->asset->store->retries(3)->retry_delay(0.1);
+  $t->app->asset->process('app.css' => "http://127.0.0.1:$port/test.css");
+
+  $t->get_ok('/')->status_is(200)->content_like(qr{Hello world});
+  $t->get_ok($t->tx->res->dom->at('link')->{href})->status_is(200)->content_like(qr{body.+color.+00f});
+  is_deeply $responses, [500, 500, 500, 200], 'right responses';
+};
+
+done_testing;
+
+__DATA__
+@@ index.html.ep
+%= asset 'app.css'
+Hello world