Added Galera autoassemble procedure description for HA cluster.

Closes-Bug: #1250573

Change-Id: Ic93640cddc1d0fb8d55b153da1039288909f81a4

pages/frequently-asked-questions/0030-howtos.rst

@@ -73,10 +73,32 @@ redeploying the environment. To do so, follow these steps:
 HowTo: Enable/Disable Galera Cluster Autorebuild Mechanism
 ----------------------------------------------------------
 
-By defaults Fuel reassembles Galera cluster automatically without need for any 
-user interaction.
+By default Fuel reassembles Galera cluster automatically without need for any 
+user interaction. The OCF script looks for existense of `mysqlprimaryinit`
+variable and tries to assemble the cluster in a following way:
 
-To prevent `autorebuild feature` you shall do::
+  - script checks for variable above and for temporary config file created
+    explicitly on deployment stage - if first is present and second missing,
+    then script enters autorebuild phase, otherwise it is skipped;
+
+  - script checks for the status of the current node - if it is syncronized
+    with quorum, procedure stops, otherwise latest epoch takes place as a
+    corosync variable parameter for selected node;
+
+  - sleep for five minutes come in place allowing other nodes to join
+    corosync quorum and push their epochs too;
+
+  - for every node in quorum script does comparison of epochs and if there is
+    at least one node with higher epoch, skips the rest and starts standalone
+    service which will join newly formed cluster later; if there is no higher
+    epochs script checks for temporary `mysqlmaster` flag and neither sets it if
+    flag does not exists nor falls back to the standalong mode;
+
+  - mysql process launches with empty `gcomm://` string forming a new quorum
+    and `mysqlmaster` deletes immediately, other nodes joins in a very short time.
+
+
+To prevent `autorebuild feature` you should do::
 
   crm_attribute -t crm_config --name mysqlprimaryinit --delete
 
@@ -84,6 +106,10 @@ To re-enable `autorebuild feature` you should do::
   
   crm_attribute -t crm_config --name mysqlprimaryinit --update done
 
+To try an automated reassemble without reboot if cluster is broken just issue::
+
+  crm resource restart clone_p_mysql
+
 .. index:: HowTo: Troubleshoot Corosync/Pacemaker
 
 How To Troubleshoot Corosync/Pacemaker