convert back to md

1 files changed, 168 insertions, 0 deletions

diff --git a/posts/2010-04-03-more-fun-with-tatsumaki-and-plack.md b/posts/2010-04-03-more-fun-with-tatsumaki-and-plack.md
new file mode 100644
index 0000000..0c926e4
--- /dev/null
+++ b/posts/2010-04-03-more-fun-with-tatsumaki-and-plack.md
@@ -0,0 +1,168 @@
+Lately I've been toying a lot with [Plack](http://plackperl.org/) and two Perl web framework: [Tatsumaki](http://search.cpan.org/perldoc?Tatsumaki) and [Dancer](http://search.cpan.org/perldoc?Dancer). I use both of them for different purposes, as their features complete each other.
+
+Plack
+-----
+
+If you don't already know what Plack is, you would want to take a look at the following Plack resources:
+
+-   [Plack (redesigned) website](http://plackperl.org)
+-   [Plack documentation](http://search.cpan.org/perldoc?Plack)
+-   [Miyagawa's screencast](http://bulknews.typepad.com/blog/2009/11/plack-and-psgi-screencast-and-feedbacks.html)
+-   [Plack advent calendar](http://advent.plackperl.org/)
+
+> As [sukria](http://www.sukria.net/) is planning to talk about [Dancer](http://perldancer.org) during the [FPW 2010](http://journeesperl.fr/fpw2010/index.html), I will probably do a talk about Plack.
+
+After reading some code, I've started to write two middleware: the first one add ETag header to the HTTP response, and the second one provides a way to limit access to your application.
+
+**\*** Plack::Middleware::ETag
+
+This middleware is really simple: for each request, an [ETag](http://en.wikipedia.org/wiki/HTTP_ETag) header is added to the response. The ETag value is a sha1 of the response's content. In case the content is a file, it works like apache, using various information from the file: inode, modified time and size. This middleware can be used with [Plack::Middleware::ConditionalGET](http://search.cpan.org/perldoc?Plack::Middleware::ConditionalGET), so the client will have the ETag information for the page, and when he will do a request next time, it will send an "if-modified" header. If the ETag is the same, a 304 response will be send, meaning the content have not been modified. This module is [available on CPAN](http://search.cpan.org/perldoc?Plack::Middleware::ETag).
+
+Let's see how it works. First, we create a really simple application (we call it app.psgi):
+
+``` perl
+    #!/usr/bin/env perl
+    use strict;
+    use warnings;
+    use Plack::Builder;
+
+    builder {
+        enable "Plack::Middleware::ConditionalGET";
+        enable "Plack::Middleware::ETag";
+        sub {
+            ['200', ['Content-Type' => 'text/html'], ['Hello world']];
+        };
+    };
+```
+
+Now we can test it:
+
+``` example
+    % plackup app.psgi&
+    % curl -D - http://localhost:5000
+    HTTP/1.0 200 OK
+    Date: Sat, 03 Apr 2010 09:31:43 GMT
+    Server: HTTP::Server::PSGI
+    Content-Type: text/html
+    ETag: 7b502c3a1f48c8609ae212cdfb639dee39673f5e
+    Content-Length: 11
+
+    % curl -H "If-None-Match: 7b502c3a1f48c8609ae212cdfb639dee39673f5e" -D - http://localhost:5000
+    HTTP/1.0 304 Not Modified
+    Date: Sat, 03 Apr 2010 09:31:45 GMT
+    Server: HTTP::Server::PSGI
+    ETag: 7b502c3a1f48c8609ae212cdfb639dee39673f5e
+```
+
+**\*** Plack::Middleware::Throttle
+
+[With this middleware](http://git.lumberjaph.net/p5-plack-middleware-throttle.git/), you can control how many times you want to provide an access to your application. This module is not yet on CPAN, has I want to add some features, but you can get the code from git. There is four methods to control access:
+
+Plack  
+Middleware::Throttle::Hourly: how many times in one hour someone can access the application
+
+P  
+M::T::Daily: the same, but for a day
+
+P  
+M::T::Interval: which interval the client must wait between two query
+
+-   by combining the three previous methods
+
+To store sessions informations, you can use any cache backend that provides `get`, `set` and `incr` methods. By default, if no backend is provided, it will store informations in a hash. You can easily modify the defaults throttling strategies by subclassing all the classes.
+
+Let's write another application to test it:
+
+``` perl
+    #!/usr/bin/env perl
+    use strict;
+    use warnings;
+    use Plack::Builder;
+
+    builder {
+        enable "Plack::Middleware::Throttle::Hourly", max => 2;
+        sub {
+            ['200', ['Content-Type' => 'text/html'], ['Hello world']];
+        };
+    };
+```
+
+then test
+
+``` example
+    % curl -D - http://localhost:5000/
+    HTTP/1.0 200 OK
+    Date: Sat, 03 Apr 2010 09:57:40 GMT
+    Server: HTTP::Server::PSGI
+    Content-Type: text/html
+    X-RateLimit-Limit: 2
+    X-RateLimit-Remaining: 1
+    X-RateLimit-Reset: 140
+    Content-Length: 11
+
+    Hello world
+
+    % curl -D - http://localhost:5000/
+    HTTP/1.0 200 OK
+    Date: Sat, 03 Apr 2010 09:57:40 GMT
+    Server: HTTP::Server::PSGI
+    Content-Type: text/html
+    X-RateLimit-Limit: 2
+    X-RateLimit-Remaining: 0
+    X-RateLimit-Reset: 140
+    Content-Length: 11
+
+    Hello world
+
+    % curl -D - http://localhost:5000/
+    HTTP/1.0 503 Service Unavailable
+    Date: Sat, 03 Apr 2010 09:57:41 GMT
+    Server: HTTP::Server::PSGI
+    Content-Type: text/plain
+    X-RateLimit-Reset: 139
+    Content-Length: 15
+
+    Over rate limit
+```
+
+Some HTTP headers are added to the response :
+
+-   **X-RateLimit-Limit**: how many request can be done
+-   **X-RateLimit-Remaining**: how many requests are available
+-   **X-RateLimit-Reset**: when will the counter be reseted (in seconds)
+
+This middleware could be a very good companion to the [Dancer REST stuff](http://www.sukria.net/fr/archives/2010/03/19/let-the-dancer-rest/) [added recently](file:///easily-create-rest-interface-with-the-dancer-1.170/).
+
+another Tatsumaki application with Plack middlewares
+----------------------------------------------------
+
+To demonstrate the use of this two middleware, [I wrote a small application](http://git.lumberjaph.net/p5-feeddiscovery.git/) with Tatsumaki. This application fetch a page, parse it to find all the feeds declared, and return a JSON with the result.
+
+``` example
+    % GET http://feeddiscover.tirnan0g.org/?url=http://lumberjaph.net/blog/
+```
+
+will return
+
+``` example
+    % [{"href":"http://lumberjaph.net/blog/index.php/feed/","type":"application/rss+xml","title":"i'm a lumberjaph RSS Feed"}]
+```
+
+This application is composed of one handler, that handle only **GET** request. The request will fetch the url given in the **url** parameter, scrap the content to find the links to feeds, and cache the result with Redis. The response is a JSON string with the informations.
+
+The interesting part is the app.psgi file:
+
+``` perl
+    my $app = Tatsumaki::Application->new(['/' => 'FeedDiscovery::Handler'],);
+
+    builder {
+        enable "Plack::Middleware::ConditionalGET";
+        enable "Plack::Middleware::ETag";
+        enable "Plack::Middleware::Throttle::Hourly",
+            backend => Redis->new(server => '127.0.0.1:6379',),
+            max     => 100;
+        $app;
+    };
+```
+
+The application itself is really simple: for a given url, the Tatsumaki::HTTPClient fetch an url, I use [Web::Scraper](http://search.cpan.org/perldoc?Web::Scraper) to find the \*link rel="alternate"\* from the page, if something is found, it's stored in Redis, then a JSON string is returned to the client.