Continuous Integration

From NEST

1 Introduction
2 Continuous Integration at NEST Initiative
3 Further reading

Introduction

Continuous Integration (CI) is a software development practice where quality control is continuously applied to the product as opposed to the traditional procedure of applying quality control after completing all development (during the so called integration phase). In essence, it is a way of decreasing the risks associated with the integration by spreading required efforts over time, which helps to improve on the quality of software, and to reduce the time taken to deliver it.

Stringent quality control is particularly important in the context of NEST, a neuronal network simulator with the emphasis on correctness, reproducibility and performance. However, given the limited amount of the available resources, it is wasteful to transfer the responsibility to re-run the test suite for all target platforms on every single code base change to the shoulders of the developers.

In order to address this problem, a Jenkins-based CI infrastructure was created during the NEST Google Summer of Code 2011 project, which would allow for regular testing of changes that are getting into the tree and timely reporting of identified problems. This way, issues will be discovered earlier and the amount of efforts to fix them will be significantly decreased (hopefully).

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Continuous Integration at NEST Initiative

The current CI implementation is now available at the following URL:

https://qa.nest-initiative.org/

At the moment, a self-signed SSL certificate is being used, which offers encryption, but not authentication. In order to use the system, you need to add an exception in your browser; the current certificate's SHA-1 fingerprint is as follows:

45 23 EA C1 6D B8 41 7C D9 32 7B A3 AF FA 6F 6E FF CA D9 F8

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Build jobs

The CI system is set up to regularly poll the version control repository hosting the main official NEST source tree. Whenever changes are detected, the latest source code is downloaded to a build executor machine and the following actions are performed:

Bootstrap the build system
Build and install NEST
Run the test suite
Bootstrap MyModule
Build and install MyModule

If any of these steps fails (returns a non-zero exit code), the build is marked as failed and a notification is sent to the developers mailing list.

Additionally, a number of metrics are collected from the build log to obtain a cumulative project "health" indicators:

Build status:
- Success (all steps completed successfully)
- Unstable (some publishers reported non-fatal errors, e.g. there were failed tests)
- Failed (a fatal error happened during the build, e.g. non-zero exit code was returned)
Weather report (how many failures there were out of 5 latest builds)
Test suite report (all JUnit-compatible reports are aggregated)
Compiler warnings report (all GCC4 / LD warnings are aggregated)

The values of these indicators are archived along with the build logs and trends can be graphed for arbitrary periods of time.

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User registration

Registered users enjoy a number of benefits as compared to the anonymous users. Most notably they may:

Access projects workspace on the build executors
Schedule / remove / edit builds manually
Be granted personal build jobs for their branches
Be allowed to create jobs (to be discussed)

Project workspace access allows one to view the source code and build directories / logs as they are on the build executor machines, which can be helpful in diagnosing build problems.

If you'd like to register with the system, please contact the administrators!

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Technical details

The infrastructure resides on a Dell PowerEdge R710 server hosted in a private BCF rack at Uni Freiburg running KVM hypervisor which controls virtual machines that host Jenkins and build executors.

The repositories hosting the up to date versions of the configuration (anubis-puppet) and documentation (anubis-docs) are available online. Please refer to these repositories for more detailed documentation regarding the setup, which is out of the scope of this brief user manual.

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