ON_CHANGE support for Junos Telemetry Interface (JTI)

OpenConfig support through Google Remote Procedure Calls (gRPC) and JTI is extended to support client streaming and bidirectional streaming of telemetry sensor information. APIs have been implemented in Junos based on Protobuf specifications released by Google for OpenConfig. These APIs perform configuration, operational state retrieval, and telemetry on Junos routers using gRPC as the transport mechanism. This implementation operates by leveraging the LEGO infrastructure to allow external customers to execute the APIs. Client streaming and bidirectional streaming are supported. With client streaming, the client sends a stream of requests to the server instead of a single request. The server typically sends back a single response containing status details and optional trailing metadata.With bidirectional streaming, both client and server send a stream of requests and responses. The client starts the operation by invoking the RPC and the server receives the client metadata, method name, and deadline.The server can choose to send back its initial metadata or wait for the client to start sending requests. The client and server can read and write in any order. The streams operate completely independently. Juniper Extension Toolkit (JET) support provides insight to users regarding the status of clients connected to JSD. JET support for gRPCI includes expanding the maximum number of clients that can connect to JSD from 8 to 30 (the default remains 5). To specify the maximum number of connections, include the max-connections statement at the [edit system services extension-service request-response grpc] hierarchy level. To provide information regarding the status of clients connected to JSD, issue the enhanced show extension-service client information command and include the clients or servers options. The clients option displays request-response client information. The servers option displays request-response server information.