Writing up Evacuation Pattern and Detected Failure doc

Updating evacuating pattern docs.

docs/evacuation_patterns.md

@@ -1,31 +1,42 @@
 # Masakari's Evacuation Patterns
 
 Masakari starts to evacuate VM instances basing on instance, process and/or
-host failures monitored by each process. This documents describes patterns about
-the evacuations executed by masakari-controller.
+host failures monitored by each process. This documents describes evacuation
+patterns executed by masakari-controller.
 
-Each monitor notifies indivisual failures to controller based on what they
-monitor. You can choose which falures of instances are rescued by Masakari,
-deploying which monitoring process or not.
+Each monitoring process notifies indivisual failures to controller based on
+what they monitor.
+You can choose which kind of failure are rescued by deploying each monitoring
+process or not.
 
 ## Evacuation patterns
 
-The section shows events that tigger Masakari to call which nova API.
+The section shows events that tigger Masakari to call nova API and evacuation patterns
+based on the events.
+Conditions when the monitoring processes send an event is listed in Detected Failure section.
 
-| Events | Monitored by | Previous instance's status | Rescue steps | Post instance's status |
+| Events Types | Monitored by | Previous instance's status | Rescue steps | Post instance's status |
 | :--- | :--- | :--- | :--- | :--- |
 | instance down | instancemonitor | active | nova.stop -> nova.start | active |
-| instance down | instancemonitor | stopped | nova.reset('stopped') | stopped |
+| instance down | instancemonitor | stopped *1 | nova.reset('stopped') | stopped |
 | instance down | instancemonitor | resized | nova.reset('error') -> nova.stop -> nova.start | active |
+| process down | processmonitor | - *2 | nova.service-disable | - |
 | host down | hostmonitor | active | nova.evacuate | active |
 | host down | hostmonitor | stopped | nova.evacuate | stopped |
 | host down | hostmonitor | resized | nova.reset('error') -> nova.evacuate | active |
 
-TBD: The table doesn't show all patterns for the evacuation now.
-Feel free to fill it out :-)
+*1 Ideally speaking, stopped instances don't exist on hosts, so instancemonitor can't send it.
+However, it could happen in some race conditions, so Masakari implements the pattern.
+
+*2 When process down occurs, masakari doesn't change instance status.
+It just changes nova-compute status to disable status not to schedule new instance onto the host.
 
 ## Detected Failures
 
-The section describes what event monitored by Masakari's monitoring processes.
+The section describes Masakari's processes monitor what failures.
 
-TBD
+| Monitoring Processes | Failures | Related Event Types |
+| :--- | :--- | :--- |
+| instancemonitor | VM instance process crush or killing a VM instance | instance down |
+| processmonitor | monitored process goes down and unable to restart it | process down |
+| hostmonitor | host status in pacemaker is changed to OFFLINE or RemoteOFFLINE | host down |