|
|
'Failover' refers to the process in which all the functions being performed by the primary server (i.e currently active-server) are automatically taken over by a redundant or standby server upon the failure or sudden termination of the primary server. This results in uninterrupted access to the application. Failover makes the Web NMS systems fault-resilient. The process of switching over has been designed to be smooth and automatic that the end user does not feel the impact of the failure of the primary server or the subsequent taking over by the standby.
Central Server and Distributed Mediation Server Failover
Web NMS has primary and standby Servers, both having the configurations and design to serve the same functionality. When the primary server fails, the standby server takes over the functions of primary and becomes the primary server. When the Central Server fails, the front-end and Distributed Mediation Server connected to it, automatically connect to the standby/secondary server. For detailed information on failover, please refer to Failover of Web NMS as the same procedure is applicable to both the Central and Distributed Mediation Servers.
What Happens to the Distributed Mediation Servers Connected to Primary Central Server ?
The Distributed Mediation Servers send/receive data to/from the primary Central Server. During the primary Central Server failover, the Distributed Mediation Servers should be configured to identify this failover and shift the communication from the primary Central Server to the standby Central Server.
The standby Central Server Name, Port, SwitchOver Interval and Retries values should be provided in the configuration file NOCServerDetails.xml present in the Distributed Mediation Server in the <DMS Home>/conf directory. When there is a failure in communication between the Distributed Mediation Server and the primary Central Server, for an interval greater than the SwitchOver Interval or for a count greater than Retries, then the data is sent to the standby Central Server at the specified port.
Configuration Parameters in NOCServerDetails.xml
The parameters present in NOCServerDetails.xml are explained below
|
Parameter |
Description |
|
NOCServerName |
Host name where the Central Server is running. |
|
NOCServerPort |
Port number in which the Central Server is running. |
|
DMSID |
ID with which the Distributed Mediation Server gets registered with the Central Server |
|
CustomerName |
Name of the customer to which this Distributed Mediation Server belongs. |
|
Organisation |
Name of the organization to which the customer belongs. |
|
ContactPerson |
Name of the contact person in the organization. |
|
ContactEmail |
E-mail address of the contact person. |
|
StandByNOCServerName |
Host name of the standby Central Server. |
|
StandByNOCServerPort |
Port number of the standby Central Server. |
|
SwitchOverInterval |
Duration after which the Distributed Mediation Server starts communicating with the standby Central Server.
|
|
Retries |
Count after which the Distributed Mediation Server starts communicating with the standby Central Server.
Note: During failover, both the values SwitchOverInterval and Retries are checked. Whichever condition is satisfied first will take precedence and failover will be affected. Both the parameters SwitchOverInterval and Retries serve the same purpose. |
|
ReEstablishInterval |
Count after which the Distributed Mediation Server contacts the Central server,once the connection is lost with the Central server
|
The communication shift from the primary Central Server to the standby Central Server is triggered based on the following configurations made in the NOCServerDetails.xml file in the <DMS Home>/conf directory.
|
S.No |
StandByNOCServerName |
StandBYNOCServerPort |
SwitchOverInterval |
Retries |
SwitchOverAction |
|
1 |
Configured |
Configured |
Configured |
Configured |
Action is triggered when the Switchover Interval or Retries exceeds the specified value. |
|
2 |
Configured |
Configured |
Configured |
Not Configured |
Action is triggered when the Switchover Interval exceeds the specified value. |
|
3 |
Configured |
Configured |
Not Configured |
Configured |
Action is triggered when the Retries exceeds the specified value. |
|
4 |
Configured |
Configured |
Not Configured |
Not Configured |
Action is based on the default SwitchOverInterval of 3600 seconds |
|
5 |
Not Configured |
Not Configured |
Not Configured |
Not Configured |
No SwitchOver action occurs. |
Sample Entries in the Configuration File
|
... <Details NOCServerName="localhost" NOCServerPort="7777" DMSID="DM" StandbyNOCServerName="Advent-Test" StandbyNOCServerPort="9800" SwitchOverInterval="3600" Retries="3" ReEstablishInterval="300"/> <CustomerDetails CustomerName="Test" Organisation="AdventNet" ContactPerson="A" ContactEmail="admin@adventnet.com"/> ... |
|
|