CRIU: Time and Space travel Service for Linux Applications
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CRIU is a tool that allows checkpointing and restoring the state of Linux applications and processes. It can be used for live migration of applications between hosts, enabling rebootless kernel upgrades, speeding up slow service startups through restoration from previous snapshots, and advanced debugging and testing use cases. CRIU works in userspace and uses kernel APIs to dump and restore process state. It has been in development for 3 years and is included in several Linux distributions. It has been tested with many common applications like Apache, nginx, databases, and more.
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More (funny) use cases
Forgot to launch your program in screen
– Live-migrate it there
Playing a game without the save button
– Snapshot it
[Put your own use case here]
http://criu.org/Usage_scenarios](https://image.slidesharecdn.com/criu-texas-linux-fest-2014-140614182445-phpapp01-150521092810-lva1-app6891/85/CRIU-Time-and-Space-travel-Service-for-Linux-Applications-22-320.jpg)
CRIU: Time and Space travel Service for Linux Applications
- 1. CRIU: Time and Space Travel Service for Linux Applications Kir Kolyshkin Texas Linux Fest, 14 Jun 2014
- 2. 2 Agenda What is CRIU? Project history and state Usage scenarios Live migration Reboot-less kernel upgrade Slow services startup Advanced debugging and testing and more...
- 3. 3 What is CRIU? Checkpoint Restore In Userspace Checkpoint or Dump Restore or Restart Full info about state
- 4. 4 CRIU pre-history ● OpenVZ project ● Containers live migration feature ● Containers → Upstream Linux ● 1500+ kernel patches from us ● Kernel-level checkpoint-restore merge failed ● User-level checkpoint-restore ...
- 5. 5 Why in userspace? Kernel User-space Dump: - ptrace - /proc - netlink - syscalls Restore: - syscalls Process kmod C/R API
- 6. 6 Some history Project started almost 3 years ago – an RFC on kernel memory API extension – small command line tool – minimal dump of process' internals First release – v0.1 -- 23 Jul 2012 (x86 and basic stuff) Since then – Kernel part completed a year ago (150+ kernel patches: new APIs for reading and setting process' state)
- 7. 7 Current project state The latest release – v1.3rc1 – supports x86_64 & ARM & AARM64 – support features that typical apps use – works on unmodified linux-3.11+ – Included into Debian, Fedora, Ubuntu, Arch, SUSE, Gentoo, CoreOS... Explicitly checked – Apache, nginx, Oracle*, mysql, mongodb – ssh/sshd, openvpn, cron, sendmail – Java, gcc, make – VNC + { gimp, mplayer, blender, supertux } – Screen + { bash, top, tcpdump, tar/bz2 } * some kernel tweaks required
- 8. 8 Some vitals - 55K lines of code - 150+ kernel patches - contribs from Google, Huawei, Samsung, Canonical
- 9. 9 Usage scenarios ● Live migration ● incl. Docker, LXC, OpenVZ containers ● Kernel upgrade w/o reboot ● Slow services startup ● Periodic snapshots (HPC) ● Advanced debugging and testing
- 10. 10 Live migration Host A Host B
- 11. 11 Live migration Host A Host B Shared FS Pre-migrate memory with memory tracker http://criu.org/P.Haul
- 12. 12 Load balancing on cluster Host A Host C Host B
- 13. 13 Power saving on cluster Host A Host C Host B
- 14. 14 Node maintenance Host A Host B
- 15. 15 Kernel upgrade w/o reboot Host Kernel A Kexec Kernel B
- 16. 16 Slow services startup time# service foo start Service readiness Spawn process Load config Top-up caches Initialize resource pools Ready T 100%
- 17. 17 Slow services startup time Tt < T Ready Spawn process 100% Service readiness # service foo restore
- 18. 18 Periodic snapshots time Memory tracker helps to keep images smaller
- 19. 19 HPC time Power failure 0% 20% 40% 60% 60%
- 20. 20 Advanced debugging Production Host Application in trouble Developer Host Debugger
- 21. 21 Advanced testing ... New test or new hardware ?
- 22. 22 More (funny) use cases Forgot to launch your program in screen – Live-migrate it there Playing a game without the save button – Snapshot it [Put your own use case here] http://criu.org/Usage_scenarios
- 23. 23 Recap ● Started as containers live-migration tool ● General tool to dump/restore apps state ● v1.2 + Linux-3.11+ can do the trick ● A lot of interesting technologies ● Memory tracker ● Migration of TCP connections ● Injecting your code into a running application ● Detecting kernel objects sharing ● etc.
- 24. 24 Resources http://criu.org – main site, documentation http://git.criu.org – git repo with tool sources http://plus.google.com/+CRIU page criu@openvz.org mailing list Kir Kolyshkin <kir@openvz.org> that's me Thank you!