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Another crazy idea (dima)
This is a set of ideas how criu can be used
This is a set of ideas how criu can be used.
== Container [[live migration]] ==
== Container live migration ==
This is the use case from what the whole checkpoint/restore project appeared. Container is checkpointed, then the image is copied on another box, then restored. From the remote observer point of view the container is just frozen for a while. You can find more details on this scenario [[LXC | here]]
This is the use case from what the whole checkpoint/restore project appeared. Container is checkpointed, then the image is copied on another box, then restored. From the remote observer point of view the container is just frozen for a while.
''For more info, see [[:Category:live migration]].''
== Slow-boot services speed up ==
== Slow-boot services speed up ==
We have a rough preliminary measurement, showing that VNC server + eclipse start time reduces from ~29 seconds to ~1.5.
We have a rough preliminary measurement, showing that VNC server + eclipse start time reduces from ~29 seconds to ~1.5.
== Reboot-less kernel upgrade ==
''Main article: [[slow-boot services speed up]].''
== Seamless kernel upgrade ==
When replacing a kernel on a box we can do it without stopping critical activity. Checkpoint it, then replace the kernel (e.g. using kexec) then restore services back. In a perfect world the applications memory shouldn't be put to disk image, but should rather be kept in RAM.
When replacing a kernel on a box we can do it without stopping critical activity. Checkpoint it, then replace the kernel (e.g. using kexec) then restore services back. In a perfect world the applications memory shouldn't be put to disk image, but should rather be kept in RAM.
''Main article: [[Seamless kernel upgrade]]''.
== Networking load balancing ==
== Networking load balancing ==
Not the whole project, but the [[TCP_connection|TCP repair]] can be used to offload an app-level request handling on another box.
Not the whole project, but the [[TCP connection|TCP repair]] can be used to offload an app-level request handling on another box.
== HPC issues ==
== HPC issues ==
Suspending a screen session and restoring it on another box might be interesting.
Suspending a screen session and restoring it on another box might be interesting.
Suspending some X app (browser?) and restoring it later is also worth thinking about but requires knowledge of X-protocol.
Suspending some X app (browser?) and restoring it later is also worth thinking about but requires knowledge of X-protocol.
''Main article: [[X applications]].''
== Processes duplication ==
== Processes duplication ==
With CRIU one can save a series of app's states (all but first incremental) and revert later to any of them. The "apply-images" item from TODO list should help to revert the state faster, especially if the memory changes tracker state is with us.
With CRIU one can save a series of app's states (all but first incremental) and revert later to any of them. The "apply-images" item from TODO list should help to revert the state faster, especially if the memory changes tracker state is with us.
One of examples when this snapshot might be useful is debugging. One might need to bring an application into a "desired" state fast, and having dump at that state would speed things up.
''Main article: [[Incremental dumps]].''
== Move "forgotten" applications into "screen" ==
== Move "forgotten" applications into "screen" ==
Sometimes it's useful to launch a process in "screen". If you forgot to switch into screen, but launched a task, criu can help to "migrate" the app into it.
Sometimes it's useful to launch a process in "screen". If you forgot to switch into screen, but launched a task, criu can help to "migrate" the app into it.
== Applications behavior analysis on another machine ==
It's possible to take periodic snapshots of running applications and transfer them on another machine for debugging or behavior and performance analysis.
== Debugging of hung application ==
If there's some service, that got hung, but need to be restarted quickly, it's possible to take a dump of one, restart and debug why it hanged later, using its restored copy.
== Fault-tolerant systems ==
With CRIU it's possible to periodically duplicate process on another box. Requires [[applying images]] facility.
== Update dryrun ==
Before updating a kernel/system libs one may duplicate a system service(s) into VM with updates and check they continue to run OK. If this test passes, then the real system update can be done.
== Zero downtime crash restore ==
Checkpoint critical service from /proc/vmcore in crash kernel and migrate on another machine.
[[Category:Using]]
[[Category:Editor help needed]]