Merge pull request #124 from Metaswitch/multi-mark-node-failed

Reviewer [EM] - Mark node failed, multiple nodes

docs/Handling_Failed_Nodes.md

@@ -48,7 +48,7 @@ To recover from this state:
 
 ## Removing a Node From a Data Store
 
-The `mark_node_failed` script can be used to remove a failed node from a back-end data store. You will need to know the type of the failed node (e.g. "sprout") and its IP address. To remove the failed node log onto a working node in the same site and run the following commands (depending on the failed node's type).
+The `mark_node_failed` script can be used to remove a failed node from a back-end data store. You will need to know the type of the failed node (e.g. "sprout") and its IP address. To remove the failed node log onto a working node in the same site and run the following commands (depending on the failed node's type). If you are removing multiple nodes simultaneously, ensure that you run the `mark_node_failed` scripts for each store type simultaneously (e.g. for multiple sprout removal, mark all failed nodes for memcached simultaneously first, and then mark all failed nodes for chronos).
 
 If you cannot log into a working node in the same site (e.g. because an entire geographically
 redundant site has been lost), you can use a working node in the other site, but in this case you