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Metrics for Ruby With Caliper

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Caliper provides metrics for Ruby projects, and it couldn't be any easier: just point Caliper to your Git repository, wait for a few seconds, and see how fit your code is.

Caliper is a free service provided by Devver, the company known for their test acceleration service (see Faster Ruby Test Execution With Devver on InfoQ). The calculation of the various metrics is done by metric_fu, wich in turn uses tools like Roodi (warns about design issues) and Saikuro (a cyclomatic complexity analyzer). Caliper aggregates all these data and provides a nice overview. For an example, take a look at these Sinatra hot spots.

Benjamin Brinckerhoff from Devver told us that they plan to integrate even more metrics:

We're not entirely sure which ones we'll add yet. This largely depends upon the responses we hear from our users. However, here are some ideas.
  • Towelie, detects duplication, similar to Flay.
  • rcov, already included in metric_fu, but not yet supported by Caliper.
  • Railroad, class diagram generator.
  • TODO detector, determines which files have the most instances of TODO (or other strings that serve as programmer notes). The exact strings would be customizable, we'd likely build this ourselves (it should be fairly easy).
When we add these tools, we plan to add them to metric_fu as well (assuming the metric_fu teams agrees they would be good additions!). In the meantime, we're working hard to make the existing metric_fu data easier to understand and work with.

Just calculating the metrics isn't enough, the code should also be refactored afterwards. This blog on Devver shows how Caliper's metrics were used to improve its own code base. Caliper also integrates well with other services like GitHub and via post-commit hooks.

The service is free for open source projects, a paid service for private projects is being considered.

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