From 0afbfaee75e8480e8e0ed0a3bbd3749a4756f727 Mon Sep 17 00:00:00 2001 From: franck cuny Date: Fri, 10 Sep 2010 23:25:10 +0200 Subject: initial import --- ...04-03-more-fun-with-tatsumaki-and-plack.textile | 166 +++++++++++++++++++++ 1 file changed, 166 insertions(+) create mode 100644 _posts/2010-04-03-more-fun-with-tatsumaki-and-plack.textile (limited to '_posts/2010-04-03-more-fun-with-tatsumaki-and-plack.textile') diff --git a/_posts/2010-04-03-more-fun-with-tatsumaki-and-plack.textile b/_posts/2010-04-03-more-fun-with-tatsumaki-and-plack.textile new file mode 100644 index 0000000..21aaa0c --- /dev/null +++ b/_posts/2010-04-03-more-fun-with-tatsumaki-and-plack.textile @@ -0,0 +1,166 @@ +--- +layout: post +category: perl +title: More fun with Tatsumaki and Plack +--- + +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. + +h3. 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/ + +.bq 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. + +h4. 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): + +{% highlight 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']]; + }; +}; +{% endhighlight %} + +Now we can test it: + +{% highlight bash %} +> 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 +{% endhighlight %} + +h4. Plack::Middleware::Throttle + +"With this middleware":http://github.com/franckcuny/plack--middleware--throttle, 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 on github. 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: + +{% highlight 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']]; + }; +}; +{% endhighlight %} + +then test + +{% highlight bash %} +$ 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 +{% endhighlight %} + +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":http://lumberjaph.net/blog/index.php/2010/03/19/easily-create-rest-interface-with-the-dancer-1170/. + +h3. another Tatsumaki application with Plack middlewares + +To demonstrate the use of this two middleware, "I've wrote a small application":http://github.com/franckcuny/feeddiscovery with Tatsumaki. This application fetch a page, parse it to find all the feeds declared, and return a JSON with the result. + +{% highlight bash %} + GET http://feeddiscover.tirnan0g.org/?url=http://lumberjaph.net/blog/ +{% endhighlight %} + +will return + +{% highlight javascript %} + [{"href":"http://lumberjaph.net/blog/index.php/feed/","type":"application/rss+xml","title":"iām a lumberjaph RSS Feed"}] +{% endhighlight %} + +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: + +{% highlight 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; +}; +{% endhighlight %} + +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. -- cgit v1.2.3