Changes

This is a set of ideas how criu can be used

This is a set of ideas how criu can be used.

== Container [[:Category:live migration|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.

== [[Slow-boot services speed up]] ==

 

== Slow-boot services speed up ==

If some service starts up too long (it can perform complex state initialization for example) we can checkpoint it after it finishes starting up and on the 2nd and subsequent starts restore it from the image.

If some service starts up too long (it can perform complex state initialization for example) we can checkpoint it after it finishes starting up and on the 2nd and subsequent starts restore it from the image.

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.

== [[Seamless kernel upgrade]] ==

 

== 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.

== 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 ==

# Periodic state save to avoid recomputation in case of a cluster crash. Take server snapshot every few minutes and put on other machine. When doing failover resurrect the other side quickly.

# Periodic state save to avoid recomputation in case of a cluster crash. Take server snapshot every few minutes and put on other machine. When doing failover resurrect the other side quickly.

== [[X applications|Desktop environment]] suspend/resume ==

== Desktop environment suspend/resume ==

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.

== Processes duplication ==

== Processes duplication ==

Some arcades require you to complete next level to "fixup" the progress. With criu it can be done at any point.

Some arcades require you to complete next level to "fixup" the progress. With criu it can be done at any point.

== [[Incremental dumps|Snapshots]] of apps ==

== Snapshots of apps ==

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.

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.

== Move "forgotten" applications into "screen" ==

== Move "forgotten" applications into "screen" ==

== Fault-tolerant systems ==

== Fault-tolerant systems ==

With CRIU it's possible to periodically duplicate process on another box. Requires [[Applying images]] facility.

With CRIU it's possible to periodically duplicate process on another box. Requires [[applying images]] facility.

== Update dryrun ==

== 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.

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.