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diff --git a/posts/2010-04-03-more-fun-with-tatsumaki-and-plack.org b/posts/2010-04-03-more-fun-with-tatsumaki-and-plack.org new file mode 100644 index 0000000..d4f1732 --- /dev/null +++ b/posts/2010-04-03-more-fun-with-tatsumaki-and-plack.org @@ -0,0 +1,209 @@ +Lately I've been toying a lot with [[http://plackperl.org/][Plack]] and +two Perl web framework: +[[http://search.cpan.org/perldoc?Tatsumaki][Tatsumaki]] and +[[http://search.cpan.org/perldoc?Dancer][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: + +- [[http://plackperl.org][Plack (redesigned) website]] +- [[http://search.cpan.org/perldoc?Plack][Plack documentation]] +- [[http://bulknews.typepad.com/blog/2009/11/plack-and-psgi-screencast-and-feedbacks.html][Miyagawa's + screencast]] +- [[http://advent.plackperl.org/][Plack advent calendar]] + +#+BEGIN_QUOTE + As [[http://www.sukria.net/][sukria]] is planning to talk about + [[http://perldancer.org][Dancer]] during the + [[http://journeesperl.fr/fpw2010/index.html][FPW 2010]], I will + probably do a talk about Plack. +#+END_QUOTE + +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 +[[http://en.wikipedia.org/wiki/HTTP_ETag][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 +[[http://search.cpan.org/perldoc?Plack::Middleware::ConditionalGET][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 +[[http://search.cpan.org/perldoc?Plack::Middleware::ETag][available on +CPAN]]. + +Let's see how it works. First, we create a really simple application (we +call it app.psgi): + +#+BEGIN_SRC 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']]; + }; + }; +#+END_SRC + +Now we can test it: + +#+BEGIN_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 +#+END_EXAMPLE + +*** Plack::Middleware::Throttle + +[[http://git.lumberjaph.net/p5-plack-middleware-throttle.git/][With this +middleware]], 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: + +#+BEGIN_SRC 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']]; + }; + }; +#+END_SRC + +then test + +#+BEGIN_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 +#+END_EXAMPLE + +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 +[[http://www.sukria.net/fr/archives/2010/03/19/let-the-dancer-rest/][Dancer +REST stuff]] +[[/easily-create-rest-interface-with-the-dancer-1.170/][added +recently]]. + +** another Tatsumaki application with Plack middlewares + +To demonstrate the use of this two middleware, +[[http://git.lumberjaph.net/p5-feeddiscovery.git/][I wrote a small +application]] with Tatsumaki. This application fetch a page, parse it to +find all the feeds declared, and return a JSON with the result. + +#+BEGIN_EXAMPLE + % GET http://feeddiscover.tirnan0g.org/?url=http://lumberjaph.net/blog/ +#+END_EXAMPLE + +will return + +#+BEGIN_EXAMPLE + % [{"href":"http://lumberjaph.net/blog/index.php/feed/","type":"application/rss+xml","title":"i'm a lumberjaph RSS Feed"}] +#+END_EXAMPLE + +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: + +#+BEGIN_SRC 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; + }; +#+END_SRC + +The application itself is really simple: for a given url, the +Tatsumaki::HTTPClient fetch an url, I use +[[http://search.cpan.org/perldoc?Web::Scraper][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. |