Using PYANG to help with JSON format

[previousqna]

All,

I’m struggling to get a rest call working for a service.

I consistently get a 400 status code that I’m guessing means my json payload is structured incorrectly.

I initially deployed the service via ncs_cli and used a “Show services …” | display JSON as a template for use in my python script.

That didn’t change the error.

Can pyang convert directly from a source .yang file to a JSON format?

I’m unable to find it documented and don’t find the option using pyang –help.

[previousqna]

Unfortunately, pyang cannot directly convert to JSON format for now.

Pyangbind might help you. It takes a little time, but It's very useful.

https://github.com/robshakir/pyangbind

Please refer to the below chapter:

Serialising a Data Instance

---

import pyangbind.lib.pybindJSON as pybindJSON

# Dump the entire instance as JSON in PyangBind format

print(pybindJSON.dumps(oclr))

---

This code snippet output JSON format data stratucure.

I am also using the library for automatically documentation from yang.

[previousqna]

Use PYANG to create REST Doc

    mkdir -p ../doc/rest
     pyang -f rest-doc --rest-doc-output=docbook --rest-doc-path=/sample --rest-doc-show-description -p $NCS_DIR/src/ncs/yang/:./yang/ yang/*.yang -o ../doc/rest/sample-doc.txt

Use XSLTPROC to create REST XTML GUIDE

xsltproc -o ../doc/rest/sample-doc.html -v docbook.xsl ../doc/rest/sample-doc.txt

[previousqna]

You can use pyang to create xml payload and then use one of the readily available xml->json tools found on-line.

Or perhaps we can help you determine the problem in the rest call/json payload that you currently have, if you provide the info here.

The show services… approach should result in accurate json payload.

[previousqna]

Another approach would be to create a service instance using the CLI, then read the instance using a rest call to see the format.

Commas and curlies will kill you…. 

[schalaga]

How can I create xml from yang. can you please give some inputs.

I tried with pyang sampl-xml-skeleton, but I am not able to produce the output.

Thanks in advance.

[Hiro Takahashi]

Hello Sujani,

Please try "-f yin" option as follows.

cisco@debian:~/NSO-4.5/examples.ncs/service-provider/mpls-vpn/packages/l3vpn/src/yang$ pyang -f yin l3vpn.yang

/home/cisco/NSO-4.5/src/ncs/yang/tailf-ncs-devices.yang:22: warning: imported module tailf-ncs-monitoring not used

<?xml version="1.0" encoding="UTF-8"?>

<module name="l3vpn"

        xmlns="urn:ietf:params:xml:ns:yang:yin:1"

        xmlns:l3vpn="http://com/example/l3vpn"

        xmlns:inet="urn:ietf:params:xml:ns:yang:ietf-inet-types"

        xmlns:tailf="http://tail-f.com/yang/common"

        xmlns:ncs="http://tail-f.com/ns/ncs">

  <namespace uri="http://com/example/l3vpn"/>

  <prefix value="l3vpn"/>

  <import module="ietf-inet-types">

    <prefix value="inet"/>

  </import>

  <import module="tailf-common">

    <prefix value="tailf"/>

  </import>

(snip)

Best regards,

Hiro

[schalaga]

Hi Hirotsugu,

Thanks for the response.

I need xml format same as service instance xml format for the given yang. I tried using yin and format is different.

Ex:

module l3vpn {

   container switch {

       leaf access {

       }

  }

}

Xml fomat:

<switch>

  <access>true</access>

</switch>

Regards,

Sujani.

[Hiro Takahashi]

Hi Sujani,

I don't think that's possible.

If we generate XML from YANG, that means you'll get a data format without any value.

On the other hand, XML in a service instance has an actual value.

There is no way to complement the value from YANG file.

Let's see your example.

module l3vpn {

   container switch {

       leaf access {

       }

  }

}

What you can get here is a container named "switch" and a leaf named "access".

There is no way to find out the leaf "access" has a value "true" as you mentioned.

I think the only way to achieve your goal is to use dry-run outformat=xml via CLI, REST or any NSO APIs.

Best regards,

Hiro

[schalaga]

yeah, I just need xml (with out any values is also fine) as you mentioned. Here I don't have an option to create service instance and take out format xml from cli or any other approaches.

I tried with sample-xml-skeleton-defaults using pyang. But not working.

[mmalysz]

How about using -f rest-doc

MMALYSZ-M-60YE:yang mmalysz$ pyang -f rest-doc --rest-doc-output=patch sample-cfs.yang

# container /samplecfs:cfs-sample

PATCH /api/running/cfs-sample

Content-Type: application/vnd.yang.data+json

{

  "cfs-sample" : {

    "sample-service-list" : {

      "sample-service-id" : "<<SAMPLE-SERVICE-ID>>",

      "sample-service-state" : "...",

      "param-1" : "param-1 value"

    }

  }

}

Then you can use json2xml

https://github.com/mbj4668/pyang/wiki/XmlJson

[schalaga]

Yeah, I was able to create JSON using rest doc. From this thread, some one replied saying, we can also generate xml from yang. Tying to find if I can directly generate xml.

But had issues with json2xml. Trying to figure it out.

root@vm--003:~# pip install json2xml

Requirement already satisfied: json2xml in /usr/local/lib/python2.7/dist-packages

Requirement already satisfied: xmltodict==0.11.0 in /usr/local/lib/python2.7/dist-packages (from json2xml)

Requirement already satisfied: six==1.11.0 in /usr/local/lib/python2.7/dist-packages (from json2xml)

Requirement already satisfied: dict2xml==1.5 in /usr/local/lib/python2.7/dist-packages (from json2xml)

Requirement already satisfied: requests==2.18.4 in /usr/local/lib/python2.7/dist-packages (from json2xml)

Requirement already satisfied: urllib3<1.23,>=1.21.1 in /usr/local/lib/python2.7/dist-packages (from requests==2.18.4->json2xml)

Requirement already satisfied: idna<2.7,>=2.5 in /usr/local/lib/python2.7/dist-packages (from requests==2.18.4->json2xml)

Requirement already satisfied: chardet<3.1.0,>=3.0.2 in /usr/local/lib/python2.7/dist-packages (from requests==2.18.4->json2xml)

Requirement already satisfied: certifi>=2017.4.17 in /usr/local/lib/python2.7/dist-packages (from requests==2.18.4->json2xml)

root@vm-schalaga-003:~# json2xml

json2xml: command not found

[kiran kotari]

Found following solution

pyang -f jtox -o employee.jtox employee.yang
json2xml -t config -o employee.xml employee.jtox sample_employee.json

[richsun]

Give https://gitlab.com/nso-developer/rest-api-explorer a try: create JSON or XML payload automatically by clicking the parameters you want to include.