A Survey of Web API client code on CPAN
Why a survey? And how do you start?
For the past few years, I've organized most of my thinking on Blogger – I first got into it while keeping various friends posted on my efforts with house renovation, and it just kind of stuck. Now I tend to start a new blog for every project I undertake. At some point (actually, on December 17, 2011) I had the bright idea that I should be able to do my task management right in Blogger as well, perhaps by the simple expedient of typing a title like "Task: do XXX" right into a blog post.
Earlier that day, I had realized that Blogger has an API, and suddenly, it was obvious how to proceed with this plan. I needed to write a Web API client to build my task indexer.
But like nearly everything I do, I was beset by the sudden fear that I might do it wrong. Maybe I'd be making assumptions I'd regret. Maybe other people were doing it better. (Note to self: this is why you never get anything done.)
I've got very little time to work on side projects – two teenagers, a full-time freelance translation business, and the aforementioned house renovation project make sure of that – so essentially everything technical is on the back burner, and so this one stayed as well, while I chewed on my fear. Occasionally in an off-moment I'd hit CPAN and look for modules that implemented other API clients, and I'd wonder what sorts of functionality might be nice in a more general Web API client support module. Finally, I just started scanning down the list of modules a search returned for "RESTful API", with the vague idea of doing a more or less comprehensive survey. Then I saw the WebService namespace and realized it contains over thirteen hundred modules. Good God. Not something I could actually survey in any meaningful way.
Clearly I needed to search CPAN in a more specifically useful manner. And just as clearly, I needed to do that locally. Which led me to CPAN::Mini. Randall Schwarz wrote this in 2002 when a colleague asked him for a CD with CPAN burned on it and he realized that the size of "the CPAN" (when did we drop the "the"? Or is it just me?) was far too large, but a "mini-CPAN" with just the latest version of each module would be 200 MB and easily fit on a CD.
As of this writing, of course, even a mini-CPAN won't fit on a CD, being 1.84 GB in over 30,000 files. But I downloaded it anyway. I have a CPAN.
What I'm going to do first is just to find all the dependencies on LWP, WWW::Curl, Net::Curl, HTTP::Client, HTTP::Client::Parallel, HTTP::Tiny, and HTTP::Lite. If I run across any other basic HTTP clients, I'll include them in the seed list as well.
No, wait, I guess what I'm going to do first is to try to come up with a more or less complete list of HTTP clients on CPAN, while whistling past the infinite-regress graveyard. (Note: this is a TODO in the article.)
Anyway, the modules we find that way will break down into three categories: (1) modules that implement an API client, (2) support modules that provide an API client framework, and (3) modules that just retrieve HTTP for other purposes, which we'll ignore. Then I'll repeat the step for the modules found in (2) to find indirect dependencies. Obviously, the tool I want is something that can take an input module name and return a list of all modules that depend on it, so I'll do that in the next section.
It might be instructive to get a list of all the URLs used in these APIs. But my ultimate goal here is to see how people are doing things, and see how many of these implementations might be useful in coming up with best Perl practices for writing a Web API client.
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