Dr. Dobb's Journal - February 2008 - (Page 10)

D02vox_p4ma 12/7/07 3:12 PM Page 10 Alia Vox by John Graham-Cumming Software Builds and the Virtual Time Machine Making efficient use of available hardware IF YOU ARE NOT yet using virtualization in your build environment, then it’s time to get moving. Applying virtual machine technology to a build system, just as many have done in the test environment, means being able to give instant answers to questions like “Can you give me the log files for build XYZ?” “Which system headers , were used for project ABC?” and it means always being able to say “Yes” when someone asks for a rebuild of an ancient software version. Fundamentally, software build man- other file they can be backed up, versioned, and reloaded when agement is about the process of getting needed. all the right software components—a If builds are performed on a virtual machine, that machine can particular version of the source, the spe- be saved and tagged with each build. Or a virtual machine “snapcific tools (such as compilers and linkers) shot” can be taken and tagged with the build number. You could and the right third-party code (such as even check the snapshot into version control when the build is system libraries)—on to a machine with tagged. the right operating system and running Now the configuration of an old build is on hand at any time. the build script. Just fire up the right VM to go back in time. You’ll be taken right Once the build script has run, the back to the moment the build finished, with the complete machine object code generated has to be extract- state available, and a cursor flashing at a shell prompt ready for the ed, source code tagged, and precious log next command. files and other output saved for later use. But keeping the complete state is not the only advantage of virFrequently, a complete record of the con- tualization. Old operating systems can be made to run on new hardfiguration of the build machine is needed ware by virtualizing the interfaces that the OS sees. It’s no longer (including tool, library, and OS versions) necessary to keep ancient hardware around—and working—if that as well as a bill-of-materials listing all the Windows 98 VM can run on the latest virtualized Intel box. source code that went into the build. Virtual machines also mean that pristine configurations are Complete, detailed records are neces- always available. The ultimate “make clean” is booting from a sary because the build machine’s configu- newly initialized virtual machine. A repository of configurations ration will inevitably change as time goes can be built and run on any machine available to the build team. by and other builds are performed on it. The problem of maintaining specific machines for specific builds But what if that were not the case? What goes from being a hardware issue to a software one. if every time the build finished, the entire And the same hardware can be used to support different OS machine was placed in a vault in case the configurations, making more efficient use of build infrastructure. build had to be reproduced? Each time the All these changes mean that software production management build manager performed a build, they’d products need to understand virtualization and help the build have to go out and buy a new machine. team manage virtual assets. If the management system is Sounds ridiculous? Yes. But wouldn’t virtualization-aware, then it can control the entire process of startit be great? ing the right virtual machines, getting sources, running builds, There would be no problem repro- archiving output, and saving virtual machine snapshots. ducing an old build when an important The latest software production management products (includcustomer demands a bug fix, or a securi- ing my company’s ElectricCommander) integrate with the classic ty headache means rereleasing old code. suite of build tools (such as SCM, scripting languages, make or ant No problem grepping an old log file. No tools, and test systems) and have been enhanced to be problem asking questions about what virtualization-aware. exactly went into a build. No need to In short, virtualization makes more efficient use of existing guess what the configuration was, or build hardware, simplifies the management of different build consweat trying to reproduce an old build. figurations, and gives the build manager a virtual time machine Happily, virtual machines turn phys- capable of taking them back to the moment when any given build ical hardware into files. And like any was completed. DDJ John is founder of Electric Cloud, which focuses on improving software production processes. He can be contacted at jgc@electric-cloud.com 10 Dr. Dobb’s Journal l www.ddj.com l February 2008 http://www.ddj.com

Table of Contents Feed for the Digital Edition of Dr. Dobb's Journal - February 2008

Dr. Dobb's Journal - February 2008 Contents Hmmmm Alia Vox Developer Diaries Developer’s Notebook South American Software Development Conversations Inside Visual Studio 2008 BibPort: Creating Bibliographic References Continuous LINQ The ZK Framework Static Testing C++ Code The Agile Edge Effective Concurrency Swaine’s Flames

Dr. Dobb's Journal - February 2008

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