---
layout: post
summary: In which I write about Tatsumaki.
title: Tatsumaki, or how to write a nice webapp in less than two hours
---
Until today, I had a script named "lifestream.pl". This script was triggered via cron once every hour, to fetch various feeds from services I use (like <a href="http://github.com/">github</a>, <a href="http://identi.ca/">identi.ca</a>, ...) and to process the result through a template and dump the result in a HTML file.
Today I was reading <a href="http://github.com/miyagawa/Tatsumaki">Tatsumaki's code</a> and some examples (<a href="http://github.com/gugod/Social">Social</a> and <a href="http://github.com/miyagawa/Subfeedr">Subfeedr</a>). Tatsumaki is a "port" <a href="http://www.tornadoweb.org/">tornado</a> (a non blocking server in Python), based on Plack and AnyEvent. I though that using this to replace my old lifestream script would be a good way to test it. Two hours later I have a complete webapp that works (and the code is available <a href="http://git.lumberjaph.net/p5-lifestream.git/">here</a>).
The code is really simple: first, I define an handler for my HTTP request. As I have only one things to do (display entries), the handler is really simple:
{% highlight perl %}
package Lifestream::Handler;
use Moose;
extends 'Tatsumaki::Handler';
sub get {
my $self = shift;
my %params = %{$self->request->params};
$self->render(
'lifestream.html',
{ memes => $self->application->memes($params{page}),
services => $self->application->services
}
);
}
1;
{% endhighlight %}
For all the get request, 2 methods are called : <strong>memes</strong> and <strong>services</strong>. The <strong>memes</strong> get a list of memes to display on the page. The services get the list of the various services I use (to display them on a sidebar).
Now, as I don't want to have anymore my lifestream.pl script in cron, I will let Tatsumaki do the polling. For this, I add a service to my app, which is just a worker.
{% highlight perl %}
package Lifestream::Worker;
use Moose;
extends 'Tatsumaki::Service';
use Tatsumaki::HTTPClient;
sub start {
my $self = shift;
my $t;
$t = AE::timer 0, 1800, sub {
scalar $t;
$self->fetch_feeds;
};
}
sub fetch_feeds {
my ($self, $url) = @_;
Tatsumaki::HTTPClient->new->get(
$url,
sub {
#do the fetch and parsing stuff
}
);
}
{% endhighlight %}
From now, every 60 minutes, feeds will be checked. Tatsumaki::HTTPClient is a HTTP client based on AnyEvent::HTTP.
Let's write the app now
{% highlight perl %}
package Lifestream;
use Moose;
extends "Tatsumaki::Application";
use Lifestream::Handler;
use Lifestream::Worker;
sub app {
my ($class, %args) = @_;
my $self = $class->new(['/' => 'Lifestream::Handler',]);
$self->config($args{config});
$self->add_service(Lifestream::Worker->new(config => $self->config));
$self;
}
sub memes {
}
sub services {
}
{% endhighlight %}
The <strong>memes</strong> and <strong>services</strong> method called from the handler are defined here. In the app method, I "attch" the "/" path to the handler, and I add the service.
and to launch the app
{% highlight perl %}
my $app = Lifestream->app(config => LoadFile($config));
require Tatsumaki::Server;
Tatsumaki::Server->new(
port => 9999,
host => 0,
)->run($app);
{% endhighlight %}
And that's it, I now have a nice webapp, with something like only 200 LOC. I will keep playing with <a href="http://www.slideshare.net/miyagawa/tatsumaki">Tatsumaki</a> as I have more ideas (and probably subfeedr too). Thanks to <a href="http://bulknews.typepad.com/">miyagawa</a> for all this code.
