While the InfoHub database is available to any reader for asynchronous access without a need to be identified in the Configuration File, an InfoHub can also notify a reader when InfoHub data has a characteristic specified in a Subscription (see "Defining a Subscription"). For example, the Reference Implementation SNMP sub-agent uses this technique to generate SNMP traps without an asynchronous external request or polling. While most of the InfoHub works independently of any adapters, in order to perform asynchronous alerts or notifications, it requires some context for the Subscriber adapters. The syntax of the Subscriber Descriptor is:

Subscriber:{InfoDictID | InfoDictName}:[SubscriberName]:[SubscriberID]
[Tip]InfoHub Internals

When a Subscription detects an alert condition it queues the item (with a timestamp) under ^InfoHubInfo(InfoHubId,"Alerts") and INTRPTs all Subscribers attached to that Subscription. The Subscriber adapter process handles the queued alert item and KILLs its descendant node at its Subscriber ID; if there are no more Subscriber descendant nodes, it KILLs the queued item.

Configuration stores Subscriber specifications in the following node:

^InfoHubConf(InfoHubID,"Subscribers",SubscriberID,BeginningSequenceNumber)=​[EndingSequenceNumber]:​InfoDictID:SubscriberName

Example:

Subscriber:Reporters:SNMP:404
Subscriber:Reporters:NAGIOS:503

This example configures two subscribers–SNMP and NAGIOS. This example is a part of SimpleMonitor.conf in the ULFM Reference Implementation.

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