Add proper handling of the "crashed" Xen state

Whenever an instance would enter the crashed state due to kernel issues
or other horrible problems, Ganeti would not be able to interpret the
data and would report strange and incomprehensible errors. This patch
fixes this by adding proper handling for the "crashed" state.

Signed-off-by: Hrvoje Ribicic <riba@google.com>
Reviewed-by: Helga Velroyen <helgav@google.com>

diff --git a/lib/hypervisor/hv_xen.py b/lib/hypervisor/hv_xen.py
index 9a68766..576b518 100644 (file)
--- a/lib/hypervisor/hv_xen.py
+++ b/lib/hypervisor/hv_xen.py
@@ -115,6 +115,15 @@ def _RunInstanceList(fn, instance_list_errors):
   return result.stdout.splitlines()
 
 
+class _InstanceCrashed(errors.GenericError):
+  """Instance has reached a violent ending.
+
+  This is raised within the Xen hypervisor only, and should not be seen or used
+  outside.
+
+  """
+
+
 def _ParseInstanceList(lines, include_node):
   """Parses the output of listing instances by xen.
 
@@ -146,6 +155,10 @@ def _ParseInstanceList(lines, include_node):
     except (TypeError, ValueError), err:
       raise errors.HypervisorError("Can't parse instance list,"
                                    " line: %s, error: %s" % (line, err))
+    except _InstanceCrashed:
+      # The crashed instance can be interpreted as being down, so we omit it
+      # from the instance list.
+      continue
 
     # skip the Domain-0 (optional)
     if include_node or data[0] != _DOM0_NAME:
@@ -240,6 +253,18 @@ def _IgnorePaused(instance_info):
   return instance_info.replace('p', '-')
 
 
+def _IsCrashed(instance_info):
+  """Returns whether an instance is in the crashed Xen state.
+
+  When a horrible misconfiguration happens to a Xen domain, it can crash,
+  meaning that it encounters a violent ending. While this state usually flashes
+  only temporarily before the domain is restarted, being able to check for it
+  allows Ganeti not to act confused and do something about it.
+
+  """
+  return instance_info.count('c') > 0
+
+
 def _XenToHypervisorInstanceState(instance_info):
   """Maps Xen states to hypervisor states.
 
@@ -250,6 +275,9 @@ def _XenToHypervisorInstanceState(instance_info):
   """
   instance_info = _IgnorePaused(instance_info)
 
+  if _IsCrashed(instance_info):
+    raise _InstanceCrashed("Instance detected as crashed, should be omitted")
+
   if _IsInstanceRunning(instance_info):
     return hv_base.HvInstanceState.RUNNING
   elif _IsInstanceShutdown(instance_info):