keepalived: Add to_backup.sh script

community-tutorials/high-availability-keepalived/01-en.md

@@ -161,7 +161,8 @@ CURL_CHECK='
     </SOAP-ENV:Body>
 </SOAP-ENV:Envelope>'
 
-REROUTE_RESULT=$(curl -s -H "Content-Type: text/xml; charset=utf-8" -H "SOAPAction:" -d "$CURL_REROUTE" -X POST https://www.servercontrolpanel.de:443/WSEndUser?xsd=1)
+# Do not trigger re-route before checking if the current may even has the correct IP
+# REROUTE_RESULT=$(curl -s -H "Content-Type: text/xml; charset=utf-8" -H "SOAPAction:" -d "$CURL_REROUTE" -X POST https://www.servercontrolpanel.de:443/WSEndUser?xsd=1)
 CHECK_RESULT=$(curl -s -H "Content-Type: text/xml; charset=utf-8" -H "SOAPAction:" -d "$CURL_CHECK" -X POST https://www.servercontrolpanel.de:443/WSEndUser?xsd=1)
 FAILOVER_IP_ACTIVE=$(echo $CHECK_RESULT | grep YOUR_FAILOVER_IP | wc -l)
 
@@ -186,6 +187,19 @@ Hints:
 - _YOUR_VSERVER_NAME_ can be found in your SCP in the _General_ section of the corresponding server.
 - _YOUR_VSERVER_MAC_ can also be found in your SCP in the _General_ section of the corresponding server (note that you need the MAC of your primary interface not the MAC of the vLAN).
 
+
+**to_backup.sh**
+
+```
+#!/usr/bin/bash
+
+# Ensure no to_master script is still running even though we got into backup state
+
+if pgrep to_master.sh; then killall to_master.sh; fi
+```
+
+The above script kills the `to_master.sh` script if it is already running on this host. This prevents a race condition where 2 servers might want the vIP routed to themselves
+
 # Step 3 - Set up Keepalived
 
 ## Step 3.1 - Install Keepalived
@@ -229,6 +243,8 @@ vrrp_instance VI_1 {
         10.132.0.100
     }
     notify_master /PATH/TO/YOUR/SCRIPT/to_master.sh
+    notify_backup /PATH/TO/YOUR/SCRIPT/to_backup.sh
+    notify_fault /PATH/TO/YOUR/SCRIPT/to_backup.sh
 }
 ```
 
@@ -249,6 +265,8 @@ vrrp_instance VI_1 {
         10.132.0.100
     }
     notify_master /PATH/TO/YOUR/SCRIPT/to_master.sh
+    notify_backup /PATH/TO/YOUR/SCRIPT/to_backup.sh
+    notify_fault /PATH/TO/YOUR/SCRIPT/to_backup.sh
 }
 ```