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Re: [Libvir] Patch to 'ping' XenD when opening connection



On Mon, Jun 12, 2006 at 11:50:36AM -0400, Daniel Veillard wrote:
> On Mon, Jun 12, 2006 at 04:01:33PM +0100, Daniel P. Berrange wrote:
> > Currently the XenD driver's implementation of the 'open' method will return
> > success, regardless of whether XenD is even present. The attached patch
> > makes the open method do a 'ping' to see if XenD is actually there, returning
> > failure if it is not. This ensures that the XenD driver backend doesn't get
> > activated when connecting to alternate non-Xen backends, such as the test
> > backend I committed last week.  
> 
>   Yes that makes sense. I think originally the point was to be able to start 
> some monitoring tool before xend was started (and it's simpler) but now
> this need fixing, you are right.
> 
> > The current 'ping' is simply to call the xenDaemonGetVersion() method since
> > that's a pretty simle & low-overhead way to testing livliness of XenD. Any
> > suggestions for a better ping - if not I'll go ahead & commit this change 
> [...]
> > +    /* A sort of "ping" to make sure the daemon is actually
> > +       alive & well, rather than just assuming it is */
> > +    if ((ret = xenDaemonGetVersion(conn, &version)) < 0) {
> 
>    hum, it seems the connection should be closed in that error case, or
> we may be leaking. Not 100% since I don't have the full context right now.
> Once checked, yes please commit :-)

Each method call in the xenDaemon code does a full HTTP connection setup & tear
down pair, so there are no resources kept open across method calls. Thus there
is no cleanup neccessary (xenDaemonClose is a no-op already).

Regards,
Dan.
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