The yang-push Stream The yang-push stream is the data in configuration and operational databases that is described by a supported YANG model. This stream supports an XPath filter to specify what data is of interest within the stream, and where the XPath expression is based on the YANG model that defines the data of interest. Update notifications for this stream can be sent either when data changes or during fixed periods, but not for both, for a given subscription. Subscriptions for data that does not currently exist are permitted, and these run as normal subscriptions. The only target database that is supported is running .
Determining On-Change Capability Currently, there is no indication within YANG models about the type of data that can be subscribed to, by using an on-change subscription. Attempts to subscribe to data that cannot be subscribed to by using on-change subscription results in a failure (dynamic) or an invalid subscription (configured). For more information on On-Change Publication, see the section, On-Change Publication for yang-push . IETF Draft Compliance Telemetry using the yang-push stream is based on the IETF NETCONF working group's early drafts for telemetry. These are:
Custom Subscription to Event Notifications, Version 03 Subscribing to YANG datastore push updates, Version 07 The following features that are described in the corresponding drafts are not supported: Note • Subtree filters • Out-of-band notifications • Any subscription parameter not explicitly stated as supported X-Path Filter for yang-push The dataset within the yang-push stream to be subscribed to should be specified by the use of an XPath filter. The following guidelines apply to the XPath expression: • XPath expressions can have keys to specify a single entry in a list or container.
The supported key specification syntax is [{key name}="{key value}"] The following is an example of an XPath expression: filter xpath /rt:routing-state/routing-instance[name="default"]/ribs/rib[name="ipv4-default"]/routes/route # VALID! Compound keys are supported by the use of multiple key specifications. Key names and values must be exact; no ranges or wildcard values are supported. Model-Driven Telemetry The yang-push Stream Model-Driven Telemetry 34