[CRIU] the new p.haul interface p.haul-wrap question

[Nikita Spiridonov]

On Mon, 2015-10-12 at 16:14 +0200, Adrian Reber wrote:
> In the past (before 'implement migration over existing connections') I
> have started p.haul-service on the destination machine and was able to
> migrate as many processes to the destination machine without restarting
> p.haul-service. Using the newly introduced p.haul-wrap this is no longer
> possible. The first connection works but the second connection just
> hangs with:
> 
> # ./p.haul-wrap client host02 pid `pidof minimal`   -v 4  -j  
> Establish connection...
> Exec p.haul: ./p.haul pid 5678 -v 4 -j --to host02 --fdrpc 3 --fdmem 4 --fdfs 5
> 14:04:33.753: Starting p.haul
> 14:04:33.753: Use existing connections, fdrpc=3 fdmem=4 fdfs=5
> 
> Which is a bit annoying as p.haul-service (or ./p.haul-wrap service) has
> to be restarted for every new migration request. Even for failed
> migration requests.
> 
> It also says pretty clear that 'p.haul-wrap' is for testing purposes
> only which is a bit confusing as there is right now no other way to use
> p.haul from the command-line.
> 
> So I am kind of missing the removed stand-alone p.haul mode as I do not
> know how to set up the required file descriptors for the communication
> between the p.haul processes.
> 
> 
> 		Adrian

The idea beside that standalone mode remotion was to remove connections
establishment from p.haul and use it exclusively for iterative disks and
memory migration. Connection establishment makes code a bit more
complicated and honestly saying when we make this decision we don't
think that it will affect somebody.

I will return standalone mode back in several days. Don't know for now
which way is better, fix "p.haul-wrap service" to serve multiple clients
or preserve connections establishment in p.haul/p.haul-service, have to
think it over.