CPAN Testers Has an API

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[Watch this lightning talk on The Perl Conference YouTube channel]

I've been working on the CPAN Testers project since 2015. In all that time, I've been focused on maintenance (which has involved more operations/administration tasks than any actual code changes) and modernization. It's that modernization effort that has led to a new CPAN Testers API.

This new API uses the Mojolicious web framework, along with an OpenAPI schema to expose all of the most useful CPAN Testers data. OpenAPI is a specification for web APIs, and there are tools like Swagger to generate a useful documentation website from your spec, like the CPAN Testers API documentation website.

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2017 Perl Toolchain Summit

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This year I had one goal for CPAN Testers: Replace the current Metabase API with a new API that did not write to Amazon SimpleDB. The current high-availability database that raw incoming test reports are written is Amazon SimpleDB behind an API called Metabase. Metabase is a highly-flexible data storage API designed to work with massive, unstructured data sets and still allow for sane organization and storage of data. Unfortunately, Amazon SimpleDB is as it says on the tin: Simple. Worse, it's expensive: Like most Amazon services, it charges for usage, so there's a huge incentive for CPAN Testers to use it as little as possible (which made some of the code quite obtuse).

So, I made a plan to excise the Metabase. Since we already cached every raw test report locally in the CPAN Testers MySQL database, I planned to write a new Metabase API that wrote directly to the cache, and then adjust the backend processing to read from the cache. I spent the better part of a month working through all the Metabase APIs, how the data was stored in the database, and how to translate between a simple JSON format and the serialized Metabase objects. However, some proper schema design prevented me from finishing this project: A single NOT NULL column could not be changed to allow nulls very easily, it being a 600GB table. The one time where a well-designed schema was a bad thing!

But then Garu, author of cpanm-reporter and CPAN::Testers::Common::Client came up with an idea to make a new test report format. These new reports would have to be stored in a new place, and I discovered that MySQL had recently started building some rich JSON tooling. Making a new JSON test report format and storing it in our new high-availability MySQL cluster seemed like a perfect solution for storing our raw test reports.

After a few weeks of discussion, I finally realized that it would be an easier task to make a backwards-compatible Metabase API write to the new test report MySQL table, even though it increased the amount of work that needed to be done:

  • Complete the new test report format schema (Garu)
  • Write the new backwards-compatibility Metabase API (Me)
  • Write a new test report processor that writes to the old Metabase cache tables (Joel Berger)
  • Write a migration script from the old Metabase cache tables to the new test report JSON object (?)

With that plan, I headed for Lyon.

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Nerds Rejecting Nerds

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https://medium.com/@maradydd/when-nerds-collide-31895b01e68c

I was linked to this article after a discussion that was triggered by a Tweet: https://twitter.com/shadowcat_mst/status/852265380156510214

In this article, the author describes a group called "weird nerds", later renamed "hackers", and goes through some of the reasons why this group is rejecting new members of their community (namely "brogrammers" and "geek feminists", a false equivalence if ever there was one).

As someone who fits the author's idea of a hacker (the classical definition of hacker, not someone who breaks into computers), and yet has never felt like part of the hacker community, there are a lot of things in here that are bad, but I'll comment for now on a couple quotes:

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Timeout for Parallel::ForkManager

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At tonight's Chicago Perl Mongers Office Hours, Ray came up with an interesting problem. While testing all of CPAN for CPAN Testers, how do you detect when a test is hanging and kill it before it takes down the entire machine? How do you simply kill a test that is taking too long? And how do you do it without having a wholly separate watchdog program?

Ray's using Parallel::ForkManager to execute testing jobs in parallel across multiple Perl installs. There are a few ways we could implement timeouts, including IPC::Run's timeout function, or the alarm Perl built-in, but these must all be implemented in the child process. It'd be nicer if we could use the parent process to watch its own children.

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Choosing a Log Level

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Like all subjective decisions in technology, which log level to use is the cause of much angry debate. Worse, different logging systems use different levels: Log4j has 6 severity levels, and Syslog has 8 severity levels. While both lists of log levels come with guidance as to which level to use when, there's still enough ambiguity to cause confusion.

When choosing a log level, it's important to know how visible you want the message to be, how big of a problem it is, and what you want the user to do about it. With that in mind, this is the decision tree I follow when choosing a log level:

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