Currently, vdsm deamon script starts (respawn) vdsm process as vdsm user, and during that vdsm starts super vdsm process as root.

• when vdsm dies, svdsm process supposed to notice and exit by itself.
• if svdsm dies, in the next proxy call by vdsm, vdsm supposed to

start new svdsm instance after verifying that old instance is dead and call it. This is super vdsm and vdsm startup design in general. --

In current implementation we have some edge cases that we need to handle:

• vsdm can try to communicate with old instance of svdsm.
• vdsm can kill wrong process that got last svdsm pid before starting

the new instance of svdsm.

• vdsm can try to communicate with svdsm before svdsm starts to serve

requests. And i guess there are many more possible senerios that can cause bugs..

As it seems, it doesn't make sense that vdsm manages root process, and can kill it..

What if svdsm will be the manager of vdsm:

• deamon script starts up svdsm instance instead of vdsm
• svdsm forks vdsm and changes its privilege (uid to vdsm)
• vdsm receives as parameter svdsm pid for sudo requests

you mean vdsm can kill svdsm? I'd suggest svdsm exports a getProxy().killSvdsm() functinon.

• when vdsm dies, svdsm will start new instance of vdsm automatically,

supervdsm poke should be change to periodically wait() and restart.

and note the crash reason to syslog.

• svdsm starts with respawn, so when svdsm dies, vdsm dies also as its

son process, and another instance of svdsm will start automatically and start new instance of vdsm.

usecase: svdsm recieve SIGTERM, (1)if svdsm waits to join vdsm in a thread: vdsm as its child process should receive signal to terminate, Using Process() to start vdsm, and if supervdsm reload SIGTERM(sigterm handler is to kill vdsm), supervdsm will never join vdsm and exit.It will just hang there.

(2)when svdsm not wait: vdsm still be alive,svdsm will need to kill vdsm at next time startup or will result in: error: [Errno 98] Address already in use when start a new vdsm to bind xmlrpc server

also, Not sure about if it is safe for svdsm to terminate vdsm because vdsm may in the middle of other activities.

Also, svdsm can init whatever vdsm needs and is limited to do as a vdsm user (check log permissions, clean old temporary files and so on if needed..)

Royce Lv has already started to work on such design here http://gerrit.ovirt.org/#/c/4145/

So my previous choice is to : 1) As root, create a new process for supervdsmServer 2) Drop privileges in the parent 3) Start vdsm in the parent

Then, if vdsm detects a problem with supervdsm, it can just exit. This will cause respawn to restart everything again. So if either process (vdsm, or supervdsm) dies, the whole thing will be respawned.

See the draft here, let's discuss about it: http://www.ovirt.org/Normalize_vdsm_start_up_process

I'm also agree with breaking these two as dependent services just as vdsmd and libvirtd. These will involve supervdsm died and vdsm reconnect, if we use key this will be security issue. So now we use key as local variable.If just use child/parent pipe, here is similar restart logic to handle.

I want to update it and push it forward.

I would like to hear more opinions and point of views on this change,

Thanks.