[CRIU] Reg unix stream checkpointing and other issues.

[Sanidhya Kashyap]

Hi,

I am using criu to checkpoint/restore sysbench tool with mysql. When I
run sysbench on the localhost where the mysql server resides, then I
am unable to checkpoint the sysbench process. It always says: 'Can't
dump half of stream unix socket connection'. You can find the criu log
(with v4 level) here: http://ur1.ca/i5xtf

Then, I went on to try checkpointing of two processes in one shot i.e.
specifying both of the processes ids in one i.e. for sysbench and for
mysql. I thought, why don't I checkpoint both of them and see how it
goes. There, I found that as it was already failing for sysbench, so
it didn't proceed ahead.

I also tried to simply dump the msyql service that keeps on running.
There also, I was unsuccessful, as I got two errors:
1) Uncollected sockets, will probably fail later.
2) can't handle non-regular mappings...

Then the checkpointing failed there as well. This link -
http://ur1.ca/i5xty provides the log of criu checkpoint with v4 level
for the mysql service.

Finally, I was successfully able to dump the sysbench over the network. #sigh

But still, I have some questions which I would like to know:
1) How can I dump the another half of unix socket connection?

2) Even if I am able to dump the another half, will the application
work when I restore it or the another half needs to do something?

3) In what conditions, do I see uncollected sockets, and non-regular mappings?

4) What is the work around for the above i.e. uncollected sockets and
non-regular mappings?

5) Is there a possibility of checkpointing multiple processes which
are sharing the resources on a single host, like unix stream and
types? If yes, then what is the way to achieve it?

Since, I am new to criu, so that's why I have so many questions.
Please, bear with it.

Thanks,
Sanidhya