The API is as simple as
srv := MakePhaulServer(config)
cln := MakePhaulClient(local, remote, config)
cln.Migrate()
* config is the PhaulConfig struct that contains pid to migrate,
memory transfer channel (file descriptor) that phaul can use
to send/receive memory and path to existing directory where
phaul can put intermediate files and images.
* local is PhaulLocal interface with (for now) the single method
- DumpCopyRestore(): method that phaul calls when it's time
to do engine-specific dump, images copy and restore on
the destination side.
Few words about the latter -- we've learned, that different
engines have their own way to call CRIU to dump a container,
so phaul, instead of dumping one by its own, lets the caller
do it. To keep-up with pre-dump stuff, the client should
not forget to do three things:
- set the TrackMem option to true
- set the ParentImg to the passed value
- set the Ps (page server) channel with 'config.Memfd'
The criu object is passed here as well, so that caller can
call Dump() on it (once we have keep_open support in libcriu
this will help to avoid additional criu execve).
The method also should handle the PostDump notification and
do images-copy and restore in it. Not sure how to wrap this
into phaul better.
* remote is PhaulRemote interface whose method should be called
on the dst side on the PhaulServer object using whatever RPC
the caller finds acceptable.
As a demonstration the src/test/main.go example is attached. To
see how it goes 'make' it, then start the 'piggie $outfile'
proggie and run 'test $pid' command. The piggie will be, well,
live migrated locally :) i.e. will appear as a process with
different pid (it lives in a pid namespace).
Changes since v2:
* Reworked the API onto local/remote/config scheme
* Added ability to configure diretory for images
* Re-used server side Criu object for final restore
Changes since v1:
* Supported keep_open-s for pre-dumps
* Added code comments about interface
* Simplified the example code
Further plans for this are
- move py p.haul to use this compiled library
- add post-copy (lazy pages) support (with Mike help)
- add image-cache and image-proxy (with Ridrigo help)
- add API/framwork for FS migration
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>
