Example for id-allocation using Templates

[gmathewk]

Hi Team,

I had some questions about id-allocation using resource-manager package. I wanted to establish the following scenario. I have some interface tunnel configs for IOS device. I want to use id-allocation for assigning the interface number when this template is assigned to a device. Is there a way in the XML template I can request for an allocation and get back the value assigned and use it ?

Do you have any example where you have used allocation ?

Regards

Georgy

[vleijon]

Hi Georgy,

Unfortunately, you will have to write a little bit of code to use the id-allocator. You can of course keep your template and apply the template from your code.

--Viktor

[gmathewk]

I think i can request for an allocation using Netconf operation. And in the device template can i use the xpath and retrieve the ID allocated for that request ?

[adam.allen]

Doesn't the resource-manager package follow the reactive-fast-map pattern, in which case it wouldn't be possible to do in templates alone.

Adam

[vleijon]

Hi Adam, it does use RFM. Which was why my instinctive answer was no. But, now that I was challenged on it I am thinking it can actually be done in this simple case. I'll try to whip up an example!

-Viktor

[adam.allen]

That would be interesting to see - I was looking at allocating ID's for IP SLA probes - but decided against adding RFM to the service just to get an ID.

[vleijon]

First of all - this is not recommended practice! Writing a few lines of code really isn't that bad.

That being said: I made it work!

I setup a simple ncs with the id-allocator, resource-manager packages, and the router ned from the examples directory. Then I did

ncs-make-package --service-skeleton template templ

and compiled the model for templ.

I modified the template a lot, see https://gist.github.com/vleijon/d2dcdffd70bfab7dcaddbdd47196505dfor full template, and created a pool named pool1 (hardcoded name):

set resource-pools id-pool pool1 range start 1 end 100

I can then create services:

admin@ncs% set tmpl demo device ex1

[ok][2018-07-14 11:35:50]

[edit]

admin@ncs% commit dry-run

cli {

    local-node {

        data +tmpl demo {

             +    device [ ex1 ];

             +}

              resource-pools {

                  id-pool pool1 {

             +        allocation demo {

             +            allocating-service /tmpl[name='demo'];

             +        }

                  }

              }

    }

}

[ok][2018-07-14 11:35:52]

[edit]

admin@ncs% commit

Commit complete.

[ok][2018-07-14 11:36:00]

[edit]

admin@ncs% exit

[ok][2018-07-14 11:36:01]

admin@ncs> request tmpl demo get-modifications

cli {

    local-node {

        data  devices {

                   device ex1 {

                       config {

                           r:sys {

                               interfaces {

              +                    interface eth5 {

              +                        description "Interface 5";

              +                    }

                               }

                           }

                       }

                   }

               }

               resource-pools {

                   id-pool pool1 {

              +        allocation demo {

              +            allocating-service /tmpl[name='demo'];

              +        }

                   }

               }

    }

}

[ok][2018-07-14 11:36:12]

And this is sort of the desired behaviour, it waits for allocation before applying the template.

[gmathewk]

Hi Viktor,

Thanks for the example. I tried this with NSO 4.6.1.3 version. But doesnt seem to work for me. I am using a cisco-ios netsim device, and i dont see the {$val} being used.

Thanks for your help in advance.

Regards

Georgy

[adam.allen]

I'd not thought about the new template features, for me I think I'd prefer a little bit of code instead of baking the complexity into the template.

Adam

[vleijon]

Georgy: I modified it for ios in the obvious ways (using config trees from the ios ned instead of the router ned),

https://gist.github.com/vleijon/8aba33485ab353ceb24203bd5fab410a and it seems to work fine for me on 4.6.1.

Adam: I agree with you. It is neat that it works, but in most cases I would pick the code route.

[gmathewk]

Thanks Viktor. Which version of resource-manager package are you using ?

Regards

Georgy

[vleijon]

I was using the versions from the NSO distribution, they don't have any nice version numbers, but are just called example:

admin@ncs> show packages package resource-manager-example

packages package resource-manager-example

package-version 0.0.0.0

description     "Resource manager package"

ncs-min-version [ 3.0 ]

directory       ./state/packages-in-use/1/resource-manager

oper-status up

[gmathewk]

I have NCS - 4.6.1.3 and resource-manager - 3.3.0

admin@ncs% commit dry-run | debug template

Fetching literal "pool1" (from file "tmpl-template.xml", line 8)

Operation 'merge' on existing node: /resource-pools/idalloc:id-pool[name='pool1'] (from file "tmpl-template.xml", line 8)

Evaluating "./name" (from file "tmpl-template.xml", line 10)

Context node: /tmpl[name='vishal']

Result:

For /tmpl[name='vishal'], it evaluates to "vishal"

Operation 'merge' on non-existing node: /resource-pools/idalloc:id-pool[name='pool1']/allocation[id='vishal'] (from file "tmpl-template.xml", line 10)

Operation 'merge' on non-existing node: /resource-pools/idalloc:id-pool[name='pool1']/allocation[id='vishal']/username (from file "tmpl-template.xml", line 11)

Evaluating "./name" (from file "tmpl-template.xml", line 11)

Context node: /tmpl[name='vishal']

Result:

For /tmpl[name='vishal'], it evaluates to "vishal"

Setting /resource-pools/idalloc:id-pool[name='pool1']/allocation[id='vishal']/username to "vishal"

Operation 'merge' on non-existing node: /resource-pools/idalloc:id-pool[name='pool1']/allocation[id='vishal']/allocating-service (from file "tmpl-template.xml", line 12)

Fetching literal "/tmpl:tmpl[tmpl:name='" (from file "tmpl-template.xml", line 12)

Evaluating "./name" (from file "tmpl-template.xml", line 12)

Context node: /tmpl[name='vishal']

Result:

For /tmpl[name='vishal'], it evaluates to "vishal"

Fetching literal "']" (from file "tmpl-template.xml", line 12)

Setting /resource-pools/idalloc:id-pool[name='pool1']/allocation[id='vishal']/allocating-service to "/tmpl:tmpl[tmpl:name='vishal']"

Processing instruction 'set-root-node': changing XPath root node to the datastore root node (from file "tmpl-template.xml", line 23)

Processing instruction 'set': evaluating expression for variable myref (from file "tmpl-template.xml", line 24)

Evaluating "concat('/tmpl:tmpl{',./name,'}')" (from file "tmpl-template.xml", line 24)

Context node: /tmpl[name='vishal']

Result: "/tmpl:tmpl{vishal}"

Processing instruction 'set': evaluating expression for variable val (from file "tmpl-template.xml", line 25)

Evaluating "/id-allocator/pool[name='pool1']/allocation[owner=$myref]" (from file "tmpl-template.xml", line 25)

Context node: /tmpl[name='vishal']

Result: empty node

Processing instruction 'if': evaluating the condition (from file "tmpl-template.xml", line 27)

Evaluating conditional expression "boolean($val)" (from file "tmpl-template.xml", line 27)

Context node: /tmpl[name='vishal']

Result: false - skipping siblings

Processing instruction 'if': skipping (from file "tmpl-template.xml", line 27)

cli {

    local-node {

        data +tmpl vishal {

             +    device [ md1 ];

             +}

              resource-pools {

                  id-pool pool1 {

             +        allocation vishal {

             +            username vishal;

             +            allocating-service /tmpl[name='vishal'];

             +        }

                  }

              }

    }

}

[gmathewk]

Also the config template you used the key 'owner'

<?set val = {/id-allocator/pool[name='pool1']/allocation[owner=$myref]}?>

But i dont see that in the xpath.

admin@ncs> show resource-pools | display xpath

/resource-pools/idalloc:id-pool[name='pool1']/allocation[id='cc']/response/id 102

/resource-pools/idalloc:id-pool[name='pool1']/allocation[id='demo']/response/id 100

/resource-pools/idalloc:id-pool[name='pool1']/allocation[id='denis']/response/id 103

/resource-pools/idalloc:id-pool[name='pool1']/allocation[id='gmk']/response/id 10

[vleijon]

First of all, you are looking at the wrong place, try

show id-allocator | display xpath

Second of all, in commit dry-run, you shouldn't expect to see a value for val, because the id-allocator hasn't had a chance to allocate it yet.