The Devver Blog

A Boulder startup improving the way developers work.

Posts Tagged ‘caliper

Announcing Gemcutter/Caliper integration

We’re extremely happy to announce that Caliper is now generating metrics for all gems pushed to Gemcutter!

By taking advantage of the new webhooks feature in Gemcutter, Caliper is alerted whenever a new version of a gem is pushed. At that point, we automatically generate metrics. In addition, every gem page on Gemcutter now features a ‘Metrics’ link to the Caliper metrics.


We’re thrilled to be generating metrics for so many great Ruby projects. As always, please send us feedback about how we can improve Caliper!

For more details on webhooks, check out the Changelog screencast by Nick Quaranto.

Many, many thanks to Nick Quaranto, Chad Fowler, and all the other supremely awesome Gemcutter contributors!


Written by Ben

February 2, 2010 at 12:09 pm

Posted in Uncategorized

Tagged with , ,

Shutting down the Devver Test Accelerator

After much deliberation, we’ve decided to shut down our Test Accelerator product on January 22nd, 2010. (the Accelerator was previously just known as “Devver”, but to clarify between our old product and Caliper, we’re referring to it as the “Accelerator” or the “Test Accelerator”).

This has been a difficult decision for us. Understandably, some people have been confused and disappointed by this news, so I wanted to take some time to explain our decision.

For over a year, we worked to build our vision of accelerated Ruby testing in the cloud. We made our share of mistakes and learned a lot in the process. Ultimately, we found the demand was too small to warrant overcoming all the technical challenges that were harder than we anticipated.

We had many different technical challenges, but it boils down to this: we underestimated the difficulty of making it simple to run Ruby/Rails tests in the cloud.

When we began working on the Accelerator, we knew we would need many features: automatic installation of gems, automatic setup of common databases, and support for Test:Unit, Shoulda, and RSpec. However, other features caught us by surprise. For instance, many projects required running daemons, such as memcached or Solr to be running when the tests executed. Also, it was common for projects to work fine on a user’s machine, but fail in the cloud due to undeclared RubyGem dependencies (or dependencies that lacked sufficient version information). Some problems were extra difficult because, due to costs, we needed to be able to run many projects on a single EC2 instance (and it’s currently not possible to create virtual machines within EC2 Xen instances).

We worked hard to overcome these challenges, but it was still too common for users to discover that running tests in the cloud required additional work on their part (or, in some cases, that their project was not supported). And even worse, users had to jump through these hoops before they could assess whether or not the Accelerator would speed up their tests enough to make the process worth it. Because the potential benefit and possible configuration time were both unknown, many users understandably gave up before they experienced the time savings of running tests in parallel. And unfortunately, the projects that were most likely to need acceleration (those with large test suites), were also the most likely to have complex dependencies and require the most setup work.

While we may have been able to solve these problems with a lot of additional engineering, we also found that only a small percentage of teams really needed test acceleration. Some teams loved our solution, because they had test suites that took 10, 20, or even 45 minutes to run. However, most projects had smaller test suites. We found that many teams didn’t mind waiting for suites that took 3-5 minutes (or, more accurately, didn’t mind enough to justify the considerable time investment of setting up tests on the Accelerator).

So, after much discussion, we decided that we needed to create a product that would help a larger set of Ruby teams and require significantly less setup to provide value. Those discussions led to Caliper, a tool to identify risky code and technical debt in Ruby code.

Focus is key in a startup, especially a small one like ours. While we considered keeping the Accelerator running in maintenance mode, we realized we could not provide the level of support our users deserve while executing effectively on Caliper. As a result, we’ve decided to shut down the Accelerator indefinitely.

We deeply appreciate each and every person who helped us with the Accelerator, either by using it, or giving us ideas, feedback, and encouragement. We could not have gotten as far as we did without the help from users, friends, and mentors.

It pains us to shut down the service and we apologize for any inconvenience this causes our users. We hope that you understand our decision and we look forward to helping you improve your code with Caliper.

(Accelerator users: if you need to speed up your tests, here are some possible alternatives to Devver: multitest, parallel_specs, Testjour, and DeepTest. I don’t have experience with these tools, so I can’t comment on how well they work myself, but you may want to check them out.)

Written by Ben

January 6, 2010 at 2:17 pm

Posted in Devver

Tagged with , , ,

Caliper: Next Steps

We released the first version of Caliper just under two months ago. Since then, we’ve fixed bugs, made improvements, and rolled out new features. The feedback we’ve gotten from the community has been encouraging and your suggestions have helped up improve Caliper each week.

Initially, we simply wanted to take an existing tool (namely, metric_fu) and make it dead simple to set up, so that all open-source projects could get access to metric data. However, our larger goal is to improve the usability, features, and data presentation in Caliper so it becomes an indispensable part of your regular Ruby development process.

To that end, I’m happy to announce that support for private projects is on the road map. We’re still working out the details, but we plan to release this feature within the next thirty days.

At the same time, we’ll work with users to figure out how we can make metrics useful enough to be a regular part of your process (by “regular”, we mean that we hope you use metrics at least once a week).

We recently put out a short survey (results here) to try to assess what features are most important for our users. By looking at the results (somewhat limited, likely due to overly wordy questions on my part) and based on some conversations I had at RubyConf, we see a few possible scenarios for where to take Caliper next.

“Code exploration”
In this scenario, you’d primarily use Caliper to jump into an existing code base, in order to help you better understand where the problematic areas are. This might be used by consultants for a project-level code review, for understanding how to start contributing to an open-source project, or even to periodically do a survey of problems of your own project. The primary features for this scenario would be our Hot Spots feature (which list the worst methods, classes, and files in the project). Important new features include a display that shows the source code with the problems displayed alongside the source.

“Quality monitoring”
In this scenario, the primary usage for Caliper is to set and maintain certain metrics thresholds within your code base. You’d set levels for the various tools and then get alerts when those thresholds are reached. Key features would include an ability to customize thresholds for each tool, a dashboard that displays offending classes and methods, and customizable notifications.

“Refactoring assistant”
In this scenario, a single developer uses Caliper to assist them in refactoring up his/her code, perhaps after reviewing a commit that will be pushed, or because a specific section of code is known to be overly complex. Caliper would both find the biggest problems and provide feedback on how refactorings change the metrics. Key features would include an improved commit-based view of metric changes as well as the ability to push code directly to Caliper before merge that code into a shared ‘master’ branch.

Do any of these scenarios resonate with you? Would you prefer one over another? Is there another scenario that would be more useful? If you are currently using metrics in your project, how do you use them and what features do you want? If you don’t currently use metrics, what features would make you change your mind? Please make your voice heard in the comments, so we can make Caliper a valuable addition to your toolbox.

Written by Ben

November 24, 2009 at 4:57 pm

Posted in Devver

Tagged with , ,

Announcing Caliper Community Statistics

For the past few months, we’ve been building Caliper to help you easily generate code metrics for your Ruby projects. We’ve recently added another dimension of metrics information: community statistics for all the Ruby projects that are currently in Caliper.

The idea of community statistics is two-fold. From a practical perspective, you can now compare your project’s metrics to the community. For example, Flog measures the complexity of methods. Many people wonder exactly defines a good Flog score for an individual method. In Jake Scruggs’ opinion, a score of 0-10 is “Awesome”, while a score of 11-20 is “Good enough”. That sounds correct, but with Caliper’s community metrics, we can also compare the average Flog scores for entire projects to see what defines a good average score.

To do so, we calculate the average Flog method score for each project and plot those averages on a histogram, like so:


Looking at the data, we see that a lot of projects have an average Flog score between 6 and 12 (the mean is 10.3 and the max is is 21.3).

If your project’s average Flog score is 9, does that mean it has only “Awesome” methods, Flog-wise? Well, remember that we’re looking at the average score for each project. I suspect that in most projects, lots of tiny methods are pulling down the average, but there are still plenty of big, nasty methods. It would be interesting to look at the community statistics for maximum Flog score per project or see a histogram of the Flog scores for all methods across all projects (watch this space!).

Since several of the metrics (like Reek, which detects code smells) have scores that grow in proportion to the number of lines of code, we divide the raw score by each project’s lines of code. As a result, we can sensibly compare your project to other projects, no matter what the difference in size.

The second reason we’re calculating community statistics is so we can discover trends across the Ruby community. For example, we can compare the ratio of lines of application code to test code. It’s interesting to note that a significant portion of projects in Caliper have no tests, but that, for the projects that do have tests, most of them have a code:test ratio in the neighborhood of 2:1.


Other interesting observations from our initial analysis:
* A lot of projects (mostly small ones) have no Flay duplications.
* Many smaller projects have no Reek smells, but the average project has about 1 smell per 9 lines of code.

Want to do your own analysis? We’ve built a scatter plotter so you can see if any two metrics have any correlation. For instance, note the correlation between code complexity and code smells.

Here’s a scatter plot of that data (zoomed in):


Over the coming weeks, we’ll improve the graphs we have and add new graphs that expose interesting trends. But we need your help! Please let us know if you spot problems, have ideas for new graphs, or have any questions. Additionally, please add your project to Caliper so it can be included in our community statistics. Finally, feel free to grab the raw stats from our alpha API* and play around yourself!

* Quick summary:


for JSON,

curl -H 'Accept:text/x-yaml'

for YAML. More details. API is under development, so please send us feedback!

Written by Ben

November 19, 2009 at 8:37 am

Posted in Development, Ruby, Tools

Tagged with ,

Announcing Caliper

If you’re anything like us, you recognize the usefulness of code quality metrics. But configuring metrics tools and linking them to your Continuous Integration system is a chore you may not have found time for. Here at Devver we’re all about taking the pain out of common development chores. Which is why we’re pleased to announce a new Devver service: Caliper.

Caliper is the easy way to get code metrics – like cyclomatic complexity and code duplication – about your project. Just go to Enter the public Git repository URL of a Ruby project. In a few moments, we’ll give you a full set of metrics, generated by the awesome metric_fu gem.

Try it out right here:

If your project is hosted on Github, we can even re-generate metrics automatically every time someone makes a commit. Just add the URL

to your project’s Post-Receive Hooks.

Caliper is currently an Alpha product. We will be be rapidly adding features and refinements over the next few weeks. If you have a problem, a question, or a feature request, please let us know!

Written by avdi

October 9, 2009 at 8:44 am