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Joe Damato

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HighLoad++ 2014

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Joe Damato

  1. 1. scaling compiled applications Joe Damato @joedamato
  2. 2. about me • Joe Damato • San Francisco, CA • i like: • systems programming • debugging • performance analysis
  3. 3. @joedamato
  4. 4. timetobleed.com
  5. 5. sassanosystems.c om
  6. 6. http://jenkins-ci.org/
  7. 7. Repeatable builds • the most important thing for compiled software • set up a build server • with jenkins (or another type of software) • backup your built objects • copying them to s3 is not a horrible idea • regardless of source control system or branching strategy, ensure you can always rebuild any version of your software
  8. 8. Jenkins problems (maybe • git plugin didn’t work on windows fixed?) • branch building is painful, jenkins API can help • getting windows build agent working is painful
  9. 9. почему? why?
  10. 10. tools for... • RPMs • DEBs • Everything else • windows installers (MSIs) • other linux/unix like OS’s • etc
  11. 11. chroot ??
  12. 12. chroot: • • • an operation that changes the apparent root directory for the current running process [...]. A program that is run in such a modified environment cannot name (and therefore normally not access) files outside the designated directory tree. (from wikipedia)
  13. 13. RPM mock https://fedorahosted.org/mock/
  14. 14. DEB pbuilder https://wiki.ubuntu.com/PbuilderHowto
  15. 15. Everything else • KVM • Amazon EC2 • other virtualization
  16. 16. KVM EC2
  17. 17. KVM • Create a base image on disk • Clone base image • Boot the cloned image • Do the build and copy built object out. • Delete cloned image when done • Base image is still pristine and can be reused.
  18. 18. Create builds in cleanroom • Avoid contaminating builds with artifacts from previous builds. • chroots help • use mock or pbuilder for RPMs and DEBs • KVM, EC2, or equivalent for everything else • Always create pristine base images and do builds in a copy. • Use SSDs
  19. 19. Tool problems • git-buildpackage can’t set changelog distribution field • signing key setup is really painful (especially for RPMs) • deb naming scheme for packages is quite painful • all tools are undocumented and very hard to actually use • recent versions of KVM provided by ubuntu fail to boot VMs sometimes
  20. 20. two types of linking.... • • dynamic linking static linking
  21. 21. static linking • calls to functions in library are resolved at compile time. • code from the library is copied into the resulting binary.
  22. 22. dynamic linking • calls to functions are resolved at runtime. • code for a library lives in it’s own object: • libblah.so.4 • libblah.dll
  23. 23. http://www.akkadia.org/drepper/no_static_linking.html
  24. 24. почему? why?
  25. 25. static linking • figure out which libraries your app needs • pick a supported major release, if possible • build and package this library • link it statically against your binary during build • you now have fewer stones to turn over when debugging
  26. 26. static linking • you will need to track your upstream deps • you will probably want to package your upstream deps • you can then point your chroots and build envs at private deb, rpm, etc repos in your internal infrastructure • merging upstream changes in becomes its own project
  27. 27. почему? why?
  28. 28. Use files • src/ •redhat5/ •some_internal_thing.c •ubuntu1204/ •some_internal_thing.c •debian6/ •some_internal_thing.c
  29. 29. Use the build system Determine which file to build at compile time.
  30. 30. Use modules • break up ifdef soup into separate files • use the build system to compile the right file at build time • this seems obvious but many C libraries and programs are full of crazy ifdef soup.
  31. 31. Use modules • very easy to fall down a rabbit hole breaking things apart • can make the build process more complicated and harder to debug
  32. 32. почему? why?
  33. 33. Capture debug symbols • DEB and RPM can both output debug packages that contain debug symbols. • output these packages. • store these and make backups. • (or just don’t strip your binary)
  34. 34. Use googlecoredumper to catch • you can use google-coredumper segfaults, bus errors, and other bad things. • you can output a coredump when this happens. • you can use this coredump and your debug symbols to figure out what is going on.
  35. 35. Plan for failure • Have a backup plan • Capture debug symbols during your automated build process. • Store them somewhere safe (and make backups). • Capture coredumps (if possible). • Use coredumps and debug symbols to figure out what happened.
  36. 36. Plan for failure • can significantly increase complexity • google coredumper can’t help if your kernel is buggy • some linux distributions don’t allow ptrace • google coredumper only supports linux
  37. 37. http://jenkins-ci.org/
  38. 38. Check things like... • Is the binary actually statically linked? • Does it get copied to the right path? • Are the right config files autogenerated? • Does the version string the program outputs match the package version? • ....
  39. 39. You also need... correctness testing.
  40. 40. RSpec is useful for this.
  41. 41. Automated Testing test every • It will be impossible to build and change on every supported platform. • Use your build server to do this for you. • Test things like: • installing/uninstalling the object • object is actually statically linked • correctness testing (RSpec can be useful)
  42. 42. Automated testing too much • Fine line between not enough and • Windows can be painful, but cygwin can help with scripting • Easy to forget about testing the actual package install/removal • Can be difficult to get working with branch builds
  43. 43. To summarize...
  44. 44. sassanosystems.c om @joedamato
  45. 45. спасиб о

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