Developing apps
  using Perl
    Anatoly Sharifulin
   YAPC::Russia 2012
Hello, World!
«Happy Perl developer»
     about me by Andy Shitov
I program in Perl less
   But it doesn't mean I love it less :-)
JFDI became JFTI
   Just F*cking Talk about It
Success-story
  of one app
And how Perl helped me/us with it
By us I mean Applifto
www.applifto.com
Our applications
Audience polling
DLTTR.com
«Why?» and «For what?»
      in details
 http://www.slideshare.net/sharifulin/ss-12313103
A powerful reason
            for me
      I was moving from LiveJournal to Posterous,
used transfer scripts and changed Twitter and Facebook
 crossposting settings when started to get replies like
                 'Tolya! Stop it! Enough!'
Current analogues
 are nice... not!
 Slow, awkward, plain, trouble working:
TwitWipe, TwitCide, Delete My Tweets, ...
«Stop managering,
let’s start programming»
     And have a talk at #yr2012 :-)
Approach and solutions
Main aims for me

• App must delete tweets quickly
• Appropriate deleting
• Cross-platform app: iOS, Android, Web, ...
Server API
         — hello, Perl!
All logic — on our server API (not Twitter API),
            clients is simple interface
Getting to know
  Twitter API
Little experience:

• Getting user profiles after login through
  Twitter on websites
• Auto-posting to Twitter with
  Net::Twitter(::Lite)
• AnyEvent::Twitter::Stream for real-time
  search (hey, @miyagawa!)
Blocking way
Task can be solved with Net::Twitter(::Lite)
LWP::UserAgent::POE
Transport may be changed in Net::Twitter(::Lite)
NO
Idea — 2 separate
   asynchronous queues
Get timeline and delete tweets using REST Twitter API
             and asynchronous requests
This has to work fast!
Authorization and OAuth
Net::OAuth::All
We've written our OAuth module long time ago,
 supports all OAuth versions (1.0, 1.0A, 2.0)
Net::OAuth::All
https://github.com/likhatskiy/Net-OAuth-All
my $oauth = Net::OAuth::All->new(
	

 consumer_secret => $conf->{consumer_secret},
	

 consumer_key => $conf->{consumer_key },

	

 token          => $data->{access_token       },
	

 token_secret   => $data->{access_token_secret},
);
$oauth
	

 ->via('GET')
	

 ->protected_resource_url('https://api.twiiter.com/...’)
	

 ->put_extra(
	

 	

 include_rts => 'true',
	

 	

 user_id     => $user->{id},
	

 	

 count      => 200,
	

 )
	

 ->request('protected_resource')
;
$oauth->to_header;
$oauth->url; # $oauth->url_with_extra;
Patched the module
            Unauthorized user:
limit of 150 requests per hour from one IP,
 not 350 requests per hour from one user
Asynchronous requests
I use Mojolicious
   Not a secret at all :-)
Mojo::UserAgent
 Mojo::IOLoop
 Good asynchronous HTTP client
my $delay = Mojo::IOLoop->delay;
for (@$tasks) {
   ...
   $delay->begin;
   $ua->get($url => {'Authorization' => $h} => sub {
       my ($ua, $tx) = @_;
       ...
       $delay->end( ... );
   });
}

say $delay->wait;
Server API
Server API
API supports GET and POST requests,
      JSON transmission format,
     response codes 200 and 50x.
Server API
   Starman + Mojolicious
Mojolicious::Plugin::ApiHelpers
Server API
 http://api.dlttr.com
package App::Api;
use App::Base -controller,
  with => [ 'App::Task', 'App::User' ];

sub error { shift->api_error(code => 1) }
sub any { shift->api_error(code => 5) }

...

1;
my $api = $r->route('/api')->to('api#', api => 1);
$api->route('/:action', action => qr/login|oauth/)->to;

my $apiu = $api->bridge->to('#auth', sign => 1);
$apiu->bridge('/task/new')->to('#task_check')
     ->route->to('#task_new');

$api->bridge('/')->to('#auth', maybe => 1, sign => 0)
    ->route->to('#hello');
10 methods,123 tests
 and documentation
 Most methods require user authorization
     and check sign (api_id + secret)
Test::Mojo
         Test::More
       Testing API methods access,
input-output data, signature check and etc.
Test::Mojo
 Test::More
A real task from a test user
All methods
       are covered
        Without Mock-objects, no check
if a correct cluster of tweets have been deleted
Too laborious
and needless
 A real cycle cannot be tested:
posting tweets – deleting – check
$t->get_ok("$url/")
  ->status_is(200)
  ->header_is('Access-Control-Allow-Origin', '*')
  ->json_content_is({hello => 'Hello DLTTR!'})
;

$t->get_ok(sign get => "$url/task/new")
  ->status_is(200)
  ->json_content_is({error => {msg =>
    'User authorization failed', code => 2}})
;
Too risky to test on
your own account :-)

— You don't care about you Twitter acc, do you?
— Yep!
— So I can delete all your tweets?
— Nooooooooooooooo!!!
Simple
         debug reguests
To check the quality of client work requests/responses
  with before_dispatch + after_dispatch may be used
Three queues
1. Queue for timelines
  Search and filters on tweets ID to delete,
      paging with since_id and max_id
1. Queue for timelines
       Max. 200 tweets per request,
   getting timeline one by one per user,
              Rate Limit check
«Limits» by Twitter
               No access to all tweets,
only the latest ~3200 or starting from any exact date,
           counter is not on zero and etc.
2. Queue for deleting
      tweets
Deleting with 'clusters' of 200 tweets, no limits.
           «Buster» or «Cannon» :-)
2. Queue for deleting
      tweets
  Error processing — Twitter API error
      doesn't always mean a failure
3. Queue for
           Push notify
                       On iOS
   Net::APNS::Persistent (also AnyEvent::APNS),
to check if tokens are valid — Net::APNS::Feedback
3. Queue for
          Push notify
                On Android
WWW::Google::C2DM and WWW::Google::ClientLogin
Database
So easy — mysql
  Storing and task orders,
      just to relax :-)
2 finer points:
1. Create correct index
         For queues
2. Disable request
        caching
select SQL_NO_CACHE * from task where ...
Site and web-version
www.dlttr.com
www.dlttr.com
Site and web-version
• Starman + Mojolicious
• Mojolicious::Plugin::I18N2
  — my fork of I18N plugin
• Mojolicious::Plugin::OAuth
  — login through Net::OAuth::All
• Mojolicious::Plugin::ShareHelpers
• Mojolicious::Plugin::UtilHelpers
Admin and statistics
«Big Brother»
All details on users, number of tasks, feedbacks
             and real-time statistics
Statistics on users
Users wall
«Ordinary» apps don't
have statistics like that
1M+ tweets deleted,
   3K+ users,
20% make purchase
      For 2 months
Promotion
Promotion on Twitter
 Following, favorites, replies and search —
             Net::Twitter(::Lite)
Promotion on Twitter
 But they blocked me three times already :-)
Summary
Positive
• Easy solution using pure Perl
  (work time is about 30 hours)
• Works fast, really fast
• Right delete tweets
• Any changes, updates, new services
  — everything's on the server, no hard
• Real-time statistics
Only one negative:
    Server's down — the app doesn't work,
users become mad, low rates and spell curses :-)
Check out DLTTR!
http://dlttr.com/app http://dlttr.com/android
                www.dlttr.com
«Seems like a simple app
 but in fact it's awesome
       and in Perl»
P. S.
At #BarCampKrr
       I had a talk
     «Developing app
  from idea to release»
(Perl wasn't mentioned)
But everything came
  down to... Perl
           «What language do you use?»,
                     «But why?»,
«Is it difficult to find programmers like those?» :-)
use Perl or die;
Thanks!
 Anatoly Sharifulin
YAPC::Russia 2012

Developing apps using Perl