xenstore reboot/crash watch

xenstore reboot/crash watch

[Ashwin Pankaj]

Hi,

I tried googling this one - but documentation on @releaseDomain key in 
xenstore seems scanty.

   1. If a client registers a watch for this key - does it get called
      every time a domain restarts / crashes ?
   2. Why can't xenstore-ls, xenstore-read et al "see" this key ?
   3. docs/misc/xenstore.txt has this to say - "WATCH                  
      <wpath>|<token>|?
              Adds a watch.
      <snip>

              <wpath> can be a <path> to watch or @<wspecial>.  In the
              latter case <wspecial> may have any syntax but it matches
              (according to the rules above) only the following special
              events which are invented by xenstored:
                  @introduceDomain    occurs on INTRODUCE
                  @releaseDomain      occurs on any domain crash or
                                      shutdown, and also on RELEASE
                                      and domain destruction

              When a watch is first set up it is triggered once straight
              away, with <path> equal to <wpath>.  Watches may be triggered
              spuriously.  The tx_id in a WATCH request is ignored."
        So would the following python code register watch for  restart
      events of ANY domain - 'watch = xswatch("@releaseDomain",
      watch_func, xshandle())' ?

- Regards,
Ashwin

Re: xenstore reboot/crash watch

[Vincent Hanquez]

Ashwin Pankaj wrote:
> Hi,
>
> I tried googling this one - but documentation on @releaseDomain key in 
> xenstore seems scanty.
>
>    1. If a client registers a watch for this key - does it get called
>       every time a domain restarts / crashes ?
>   
yes
>    2. Why can't xenstore-ls, xenstore-read et al "see" this key ?
>   
this is not a database key. this is just a special event.
>         So would the following python code register watch for  restart
>       events of ANY domain - 'watch = xswatch("@releaseDomain",
>       watch_func, xshandle())' ?
>   
yes it seems right.
but it's not a restart event, the event is there to notify that one or 
multiple domain(s) are dead.

-- 
Vincent