Standby filter

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In a failover deployment, the standby filter is used by the backup domain in a failover pair. That means the backup domain when the primary is active, or the primary domain if the backup is active. The standby filter only allows health check (ItnmHealthCheck) events through the Event Gateway. These events are passed to the Failover plugin and tell the system to switch back to primary mode. Note that for failover behaviour, any modifications to this filter must still ensure that the standby filter accepts health check events.

When the primary server is active, the Event Gateway on the backup server does not perform any event enrichment. When the primary server is down and the backup server is active, the Event Gateway on the backup server performs event enrichment of events in the ObjectServer.

The standby filter is configured in the EventGatewaySchema.cfg configuration file. This file is located at: $NCHOME/etc/precision/EventGatewaySchema.cfg.

The example below shows how the standby filter is configured in the EventGatewaySchema.cfg configuration file.

The section of code that is relevant to the standby filter is listed in the following lines. This insert configures the Event Gateway to only pass ItnmHealthCheck events when the primary server is down and the backup server is active.

The following table describes the relevant lines from this insert:
Table 1. Lines of code relevant to the standby filter
Line numbers Description
1 Configure the incoming filter by making an insert into the config.nco2ncp table.
4 Specify an insert into the StandbyEventFilter field of the config.nco2ncp table.
11 Set the filter as follows:

"EventId in ('ItnmHealthChk', 'ItnmDatabaseConnection')",

This clause only passes events that have the event ID set to the value ItnmHealthChk or ItnmDatabaseConnection.
The following table describes the relevant lines from this insert.
insert into config.nco2ncp
(
    EventFilter,
    StandbyEventFilter,
    FieldFilter
)
values
(
    "LocalNodeAlias <> '' and (NmosDomainName = 
        '$DOMAIN_NAME' or NmosDomainName = '')",
    "EventId in ('ItnmHealthChk', 'ItnmDatabaseConnection')",
    [
        "Acknowledged",
        "AlertGroup",
        "EventId",
        "FirstOccurrence",
        "LastOccurrence",
        "LocalNodeAlias",
        "LocalPriObj",
        "LocalRootObj",
        "Manager",
        "NmosCauseType",
        "NmosDomainName",
        "NmosEntityId",
        "NmosEventMap",
        "NmosManagedStatus",
        "NmosObjInst",
        "NmosSerial",
        "Node",
        "RemoteNodeAlias",
        "EventId",
        "Serial",
        "ServerName",
        "Severity",
        "Summary",
        "SuppressEscl",
        "Tally",
        "Type"
    ]
);