+def _CheckNodeFreeMemory(cfg, node, reason, requested):
+ """Checks if a node has enough free memory.
+
+ This function check if a given node has the needed amount of free
+ memory. In case the node has less memory or we cannot get the
+ information from the node, this function raise an OpPrereqError
+ exception.
+
+ Args:
+ - cfg: a ConfigWriter instance
+ - node: the node name
+ - reason: string to use in the error message
+ - requested: the amount of memory in MiB
+
+ """
+ nodeinfo = rpc.call_node_info([node], cfg.GetVGName())
+ if not nodeinfo or not isinstance(nodeinfo, dict):
+ raise errors.OpPrereqError("Could not contact node %s for resource"
+ " information" % (node,))
+
+ free_mem = nodeinfo[node].get('memory_free')
+ if not isinstance(free_mem, int):
+ raise errors.OpPrereqError("Can't compute free memory on node %s, result"
+ " was '%s'" % (node, free_mem))
+ if requested > free_mem:
+ raise errors.OpPrereqError("Not enough memory on node %s for %s:"
+ " needed %s MiB, available %s MiB" %
+ (node, reason, requested, free_mem))
+
+