[Xen-devel] PATCH: Ignore errors from dieing domains in RPC server

["Daniel P. Berrange" <berrange@xxxxxxxxxx>]

When a domain is in the process of shutting down there is a small window
when the domain is known to XenD, but it will be unable to form an SXPR
for it due it being in the middle of device hot-unplug. This causes the
'xm list' command to totally fail with an error like

# xm list
Error: Device 0 not connected
Usage: xm list [options] [Domain, ...]

List information about all/some domains.
  -l, --long                     Output all VM details in SXP
  --label                        Include security labels


The 'xm list' command calls into the 'domains' method of XMLRPCServer.py
in XenD. This method just iterates over the list of domains, fetching
the sxpr for each in turn, but with no exception handling. So if a single
domain fails to generate an sxpr, no data is returned even for other
domains which are still functional.  This patch simply makes XenD ignore
and skip over domains which throw an exception, logging the problematic
domain.

NB, this problem only hits 'xm list' if it is configured to use the legay
XMLRPC server instead of XenAPI.

   Signed-off-by: Daniel P. Berrange <berrange@xxxxxxxxxx>

diff -r 27aaff984b36 tools/python/xen/xend/server/XMLRPCServer.py
--- a/tools/python/xen/xend/server/XMLRPCServer.py      Thu Jul 10 17:33:23 
2008 +0100
+++ b/tools/python/xen/xend/server/XMLRPCServer.py      Fri Jul 11 12:28:02 
2008 +0100
@@ -64,7 +64,14 @@
 def domains_with_state(detail, state, full):
     if detail:
         domains = XendDomain.instance().list_sorted(state)
-        return map(lambda dom: fixup_sxpr(dom.sxpr(not full)), domains)
+        ret = []
+        for dom in domains:
+            try:
+                ret.append(fixup_sxpr(dom.sxpr(not full)))
+            except:
+                log.warn("Failed to query SXPR for domain %s" % str(dom))
+                pass
+        return ret
     else:
         return XendDomain.instance().list_names(state)
 


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