Infrastructure as Code (IaC) is a novel paradigm that makes system administrators’ work quite  similar to the work of programmers. In fact, today system administrators (sysadmins) do not have to  manually perform the provisioning, configuration, and deployment processes as they can exploit some  IaC languages to write pieces of code which automate such processes and can be executed more and  more times.

Thanks to this possibility, infrastructural code can become part of the whole codebase associated  to a certain software system and can, therefore, be maintained, verified, fixed and optimized using  approaches similar to those adopted for traditional software code.

IaC languages are always associated to corresponding engines that interpret the IaC code and  execute it. In almost all cases each language is specific to a particular engine. The only  exception is TOSCA, which is a standard language supported by a variety of engines, e.g., Cloudify,  Opera and Brooklyn (this last one supports also another language).

The combination of IaC languages and the corresponding engines allow people without sysadmin  skills, e.g., application logic developers, to execute the set up of a whole software system, thus  easily replicating the application operational environment. This capability is an important  enabling factor for DevOps practices as it improves the ability of developers to run complete  complex systems, get a clue about their actual behavior, and identify possible optimizations.  Moreover, it allows the Dev and Ops sub-teams to work in a coordinated way and to be aware of each  other's activities.

Since open source software development is often the place where innovative approaches and practices  are applied, we have been trying to assess the adoption of IaC in open source projects.

With this objective in mind, we have analysed the situation in GitHub. We have considered the  population of active repositories, i.e., the highly rated (ten stars) repositories with at least  one commit from 2018, these are 460,155. Within this population, we have searched for those that  include in their description some reference to well-known IaC languages. In Table 1, the first and  second columns show the results of this analysis with reference to those languages that, according  to [1], are the most well- known and used. In total, about 1.3% of the repositories in the initial  population includes some reference to IaC in their description. This number can be considered a  sort of lower bound for the actual number as we expect that there are repositories storing IaC but  not referring to this explicitly in their description.

This is because IaC is a support code and, as such, not necessarily mentioned among the most  relevant characteristics of an application. Moreover, this percentage, even if small, is still  significant considering that IaC is a relatively new technology. To give an idea, according to [2],  Matlab is the 10th most used programming language with a share of 2%.

In terms of popularity of the various IaC languages, the analysis confirms the findings published  in [1] and based on the results of a survey with 44 respondents. The most referenced languages are  Kubernetes (2,269 repositories),  Ansible (1,620 repositories) and Terraform (561 repositories)  (see the second column of Table 1). Conversely, TOSCA, which is the only standardization effort in  the list, still features a limited adoption in the open source context we have considered.

While an in depth analysis of IaC bugs is the subject of our future work, we have started analysing  the commit history of some of those repositories that include IaC. Due to the limitations of the  querying API offered by GitHub, we could select at most 1,000 repositories for each of the IaC  languages we have considered. This has allowed us to consider 4,240 repositories (see the third  column in Table 1). These show an average percentage of IaC code that vary from being less than 1%  to about 15% (see the seventh column in Table 1), with an average number of LOC for IaC software  which is below 200 (see the sixth column in Table 1). It is interesting to see that some  maintenance activities are specifically dedicated to IaC, with an average number of commits due to  bug fixing on IaC code that varies between the 121 of Puppet (20 commits per year) and the 4 of  Brooklyn (0.67 per year) (see the fifth column of Table 1), with most repositories that see at  least one commit per year from the time the first IaC file has

appeared in the repository (eighth column) to the current time. Looking at the specific  characteristics of the languages we have considered, it seems that configuration languages such as  Puppet and Chef need more files compared to those other languages which are focusing on  orchestrating a complete deployment process.

Language/toolTotal population per IaC languageNumber of extracted repositoriesTotal number of bug commitsAvg number of bug commits in repoAvg number of LOC in IaC filesAvg percentage IaC files in repoFirst IaC file addition in repo

Language/tool Total population per IaC language Number of extracted repositories Total number of bug commits Avg number of bug commits in repo Avg number of LOC in IaC files Avg percentage IaC files in repo First IaC file addition in repo
Salt 74 74 732 13.81 50.20 9.48% 2013-04-26
Brooklyn 14 14 4 4.00 67.45 0.33% 2015-12-16
TOSCA 23 23 27 6.75 111.25 1.34% 2015-10-26
Cloudformation 223 223 105 6.18 219.58 6.53% 2014-04-19
Terraform 561 561 4233 14.35 81.19 9.72% 2015-02-03
Docker Compose 332 332 436 4.89 38.25 3.45% 2015-02-27
Packer 179 179 866 20.14 172.52 4.85% 2013-07-18
Puppet 180 180 18595 120.75 79.91 11.84% 2007-08-07
Kubernetes 2269 1000 5218 64.42 159.29 2.68% 2015-09-01
Chef 290 290 9201 38.49 81.81 14.54% 2009-01-17
Vagrant 364 364 223 4.37 55.43 2.75% 2012-02-14
Ansible 1,620 1000 8212 28.22 61.98 5.63% 2012-10-19
Total 6129 4240 47852 326.36 1178.87

Table 1. Analysis of IaC languages adoption in GitHub.

We do not yet know the causes and the implications of the differences we have highlighted, but our analysis certainly shows a significant interest in the open source community around IaC. Also, it shows the presence of a significant number of languages, some of which were born only recently (for instance, from Table 1 we can see that the first Kubernetes file has been included in a repository in 2015, but are already quite well-known and adopted.

The SODALITE project will enter in this scenario with the objective of offering tools that make possible the adoption of multiple IaC languages and tools for managing complex and highly heterogeneous software systems and that, at the same time, allows users to abstract from the peculiarities of such languages by exploiting a high level modeling language and inference mechanisms that guide the IaC definition process.

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