Playing with NSO API and Postman

[jeyriku]

Hi Team,

I wondered with there was some sort of "standard" to achieve a get request from NSO API ?

As you might notice i am quite new to APIs, Restconf, whatever...and wondered if we could easily browse NSO CDB using restconf get requests without a documentation.

I spent a couple of minutes to build a correct request and finally remembered that NSO could do it for me thanks to CLI

Here was the request :

http://jeysrv03:82/restconf/data/tailf-ncs:devices/device=jeycisco01/config/tailf-ned-cisco-ios:hostname

This request aimed to retrieve the hostname of my router.

and the command i passed to NSO CLI to retrieve the correct path to be put in my request :

admin@ncs# show running-config devices device jeycisco01 config hostname | display restconf
/restconf/data/tailf-ncs:devices/device=jeycisco01/config/tailf-ned-cisco-ios:hostname Jeycisco01

I was wondering how & why this path was built, espacially this part,

/restconf/data/tailf-ncs:devices/device=jeycisco01/config/tailf-ned-cisco-ios:hostname

Can someone explain the relationship between this path in my request and the CDB tree and tell me why there is no exact match between the URL i have to provide and the path i can see from Postman.

When browsing the datas through Postman i can not see any reference to tailf-ncs in the Yang tree as well as tailf-ned-cisco-ios, which lead me to form bad request.

Thanks in advance for your help !

Jerems

[rhinst001 · Accepted solution]

That identifies the name of the yang module where that node is defined.

From the restconf API docs:

This is how RESTCONF handle namespaces, where the prefix is the YANG module name and the namespace is as defined by the namespace statement in the YANG module.

If multiple path segments come from the same module, you only need prefix the first one.

You can find the core NSO yang models in the src/ncs/yang subdirectory of your NSO installation directory, but with includes and all, it can take some effort to trace around and figure out which module defines the specific node you're trying to access. That's what makes " | display restconf" so handy.

By the way, another good thing to understand about how the restconf paths get constructed is that the second path segment in your URL ("data") is what you use to retrieve configuration data from CDB.  If you want to invoke an rpc via restconf, you would change that path segment from "data" to "operations". For example: http://myserver:8080/restconf/operations/tailf-ncs:devices/device=JUNIPER1/rpc/rpc-ping/ping

[Nabsch · Accepted solution]

Hello Jerems,

I hope this link might help you . In order to access to data the URL is something like /restconf/data/module-name:identifier.

pyang -f tree tailf-ned-cisco-ios.yang --tree-path /hostname   --ignore-errors
module: tailf-ned-cisco-ios
  +--rw hostname?   string

In your example you want to access to the leaf hostname that is part of the module tailf-ned-cisco-ios

If you check the cdb . You can find the prefix

admin@ncs# show running-config devices device NETSIM0 config hostname | display prefixes
ncs:devices ncs:device NETSIM0
 ncs:config
  ios:hostname TEST
 !
!

Here yang file that refers to the prefix

module tailf-ned-cisco-ios {
namespace "urn:ios";
prefix ios;