Using gNMI with YDK¶

Writing the app¶

In this example, we set some BGP configuration using the Cisco IOS XR model, the CRUD (Create/Read/Update/Delete) service and the gNMI service provider. The example in this document is a simplified version of the more complete sample that is available in core/samples/bgp_gnmi_create.cpp. Assuming you have performed the core and cisco-ios-xr bundle installations first, that more complete sample can be run with the below steps:

ydk-cpp$ cd gnmi/samples
samples$ mkdir build && cd build
build$ cmake .. && make
build$ ./bgp_gnmi_create http://<username>:<password>@<host-address>:<port> [-v]

Header includes¶

In our example YDK application, first, let us include the necessary header files

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#include <iostream>
#include <spdlog/spdlog.h>

#include <ydk/crud_service.hpp>
#include <ydk/path_api.hpp>
#include <ydk/gnmi_provider.hpp>
#include <ydk/types.hpp>

#include <ydk_cisco_ios_xr/Cisco_IOS_XR_ipv4_bgp_cfg.hpp>
#include <ydk_cisco_ios_xr/Cisco_IOS_XR_ipv4_bgp_datatypes.hpp>

// indicate the namespaces being used (optional)
using namespace std;
using namespace ydk;
using namespace Cisco_IOS_XR_ipv4_bgp_cfg;
using namespace Cisco_IOS_XR_ipv4_bgp_datatypes;

gNMI service provider¶

The first step in any application is to create a service provider instance. In this case, the gNMI service provider is responsible for mapping between the CRUD service API and the underlying manageability protocol (gNMI).

We first instantiate a Repository using the location of the schema cache of the gNMI instance. We instantiate an instance of the service provider that can communicate using GRPC with an gNMI instance running at host address: 127.0.0.1 and port: 50051

// In this case, we have a GRPC service with this schema cache location
path::Repository repo{"/Users/home/distribution-karaf-0.5.2-Boron-SR2/cache/schema"};
gNMIServiceProvider gnmi_provider{repo, "127.0.0.1", 50051, "admin", "admin"};

Using the model APIs¶

After establishing the connection, we instantiate the entities and set some data. Now, create an Cisco IOS XR BGP configuration object and set the attributes

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// Create BGP object
auto bgp = make_unique<Bgp>();

// BGP instance
auto instance = make_shared<Bgp::Instance>();
instance->instance_name = "test";
auto instance_as = make_shared<Bgp::Instance::InstanceAs>();
instance_as->as = 65001;
auto four_byte_as = make_shared<Bgp::Instance::InstanceAs::FourByteAs>();
four_byte_as->as = 65001;
four_byte_as->bgp_running = Empty();

// global address family
auto global_af = make_shared<Bgp::Instance::InstanceAs::FourByteAs::DefaultVrf::Global::GlobalAfs::GlobalAf>();
global_af->af_name = BgpAddressFamilyEnum::ipv4_unicast;
global_af->enable = Empty();
four_byte_as->default_vrf->global->global_afs->global_af.append(global_af);

// add the instance to the parent BGP object

instance_as->four_byte_as.append(four_byte_as);
instance->instance_as.append(instance_as);
bgp->instance.append(instance);

Invoking the CRUD Service¶

The CRUD service provides methods to create, read, update and delete entities on a device making use of the session provided by a service provider. In order to use the CRUD service, we need to instantiate the CrudService class

CrudService crud_service{};

We can obtain the ServiceProvider instance corresponding to this node using: gNMIServiceProvider provider{repo, address};.

Finally, we invoke the create method of the CrudService class passing in the service provider instance and our entity, bgp

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try
{
  crud_service.create(provider, *bgp);
}
catch(YError & e)
{
  cerr << "Error details: " << e.what() << endl;
}

Note if there were any errors the above API will raise an exception with the base type YServiceError

Logging¶

YDK uses the spdlog logging library. The logging can be enabled as follows by creating a logger called “ydk”. For other options like logging the “ydk” log to a file, see the spdlog reference.

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if(verbose)
{
  auto console = spdlog::stdout_color_mt("ydk");
}