Results tagged “Plack”

Recently I’ve been reviewing how various Perl frameworks and modules generate HTTP headers. After reviewing several approaches, it’s clear that there are two major camps: those which put the response headers in a specific order and those which don’t. Surely one approach or the other would seem like it would be more spec-compliant, but RFC 2616 provides conflicting guidance on this point.

The bottom line is that spec says that “the order in which header fields with differing field names are received is not significant”. But then it goes on to say that it is a “good practice” (and it puts “good practice” in quotes) to order the headers a particular way. So, without strict guidance from the spec about the importance of header ordering, it would be interesting to know if header order caused a problem in practice.

The Plack::Middleware::RearrangeHeaders documentation suggests there is some benefit to strict header ordering: “to work around buggy clients like very old MSIE or broken HTTP proxy servers”

You might wonder what the big deal is— why not just stick to the “good practice” recommendation all the time? The difference can be seen in the benchmarks provided by HTTP::Headers::Fast. By ignoring the good-practice header order, an alternate implementation was able to speed-up header generation to be about twice as fast. Considering that a web-app needs to generate a header on every single request, making header generation smaller and faster is potentially a tangible win, while also still being spec-compliant.