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This library wraps gNMI functionality to ease usage with Cisco implementations.

Project description

cisco-gnmi-python

License Code style: black

This library wraps gNMI functionality to ease usage with Cisco implementations in Python programs. Derived from openconfig/gnmi.

Usage

pip install cisco-gnmi
python -c "import cisco_gnmi; print(cisco_gnmi)"

This library covers the gNMI defined capabilities, get, set, and subscribe RPCs, and helper clients provide OS-specific recommendations. As commonalities and differences are identified this library will be refactored as necessary.

It is highly recommended that users of the library learn Google Protocol Buffers syntax to significantly ease usage. Understanding how to read Protocol Buffers, and reference gnmi.proto, will be immensely useful for utilizing gNMI and any other gRPC interface.

ClientBuilder

Since v1.0.0 a builder pattern is available with ClientBuilder. ClientBuilder provides several set_* methods which define the intended Client connectivity and a construct method to construct and return the desired Client. There are several major methods involved here:

    set_target(...)
        Specifies the network element to build a client for.
    set_os(...)
        Specifies which OS wrapper to deliver.
    set_secure(...)
        Specifies that a secure gRPC channel should be used.
    set_secure_from_file(...)
        Loads certificates from file system for secure gRPC channel.
    set_secure_from_target(...)
        Attempts to utilize available certificate from target for secure gRPC channel.
    set_call_authentication(...)
        Specifies username/password to utilize for authentication.
    set_ssl_target_override(...)
        Sets the gRPC option to override the SSL target name.
    set_channel_option(...)
        Sets a gRPC channel option. Implies knowledge of channel options.
    construct()
        Constructs and returns the built Client.

Initialization Examples

ClientBuilder can be chained for initialization or instantiated line-by-line.

from cisco_gnmi import ClientBuilder

builder = ClientBuilder('127.0.0.1:9339')
builder.set_os('IOS XR')
builder.set_secure_from_target()
builder.set_call_authentication('admin', 'its_a_secret')
client = builder.construct()

# Or...

client = ClientBuilder('127.0.0.1:9339').set_os('IOS XR').set_secure_from_target().set_call_authentication('admin', 'its_a_secret').construct()

Using an encrypted channel automatically getting the certificate from the device, quick for testing:

from cisco_gnmi import ClientBuilder

client = ClientBuilder(
    '127.0.0.1:9339'
).set_os('IOS XR').set_secure_from_target().set_call_authentication(
    'admin',
    'its_a_secret'
).construct()

Using an owned root certificate on the filesystem:

from cisco_gnmi import ClientBuilder

client = ClientBuilder(
    '127.0.0.1:9339'
).set_os('IOS XR').set_secure_from_file(
    'ems.pem'
).set_call_authentication(
    'admin',
    'its_a_secret'
).construct()

Passing certificate content to method:

from cisco_gnmi import ClientBuilder

# Note reading as bytes
with open('ems.pem', 'rb') as cert_fd:
    root_cert = cert_fd.read()

client = ClientBuilder(
    '127.0.0.1:9339'
).set_os('IOS XR').set_secure(
    root_cert
).set_call_authentication(
    'admin',
    'its_a_secret'
).construct()

Usage with root certificate, private key, and cert chain:

from cisco_gnmi import ClientBuilder

client = ClientBuilder(
    '127.0.0.1:9339'
).set_os('IOS XE').set_secure_from_file(
    root_certificates='rootCA.pem',
    private_key='client.key',
    certificate_chain='client.crt',
).set_call_authentication(
    'admin',
    'its_a_secret'
).construct()

Client

Client is a very barebones class simply implementing capabilities, get, set, and subscribe methods. It provides some context around the expectation for what should be supplied to these RPC functions and helpers for validation.

Methods are documented in src/cisco_gnmi/client.py.

NXClient

NXClient inherits from Client and provides several wrapper methods which aid with NX-OS gNMI implementation usage. These are subscribe_xpaths, and the removal of get and set as they are not yet supported operations. These methods have some helpers and constraints around what is supported by the implementation.

Methods and usage examples are documented in src/cisco_gnmi/nx.py.

XEClient

XEClient inherits from Client and provides several wrapper methods which aid with IOS XE gNMI implementation usage. These are delete_xpaths, get_xpaths, set_json, and subscribe_xpaths. These methods have some helpers and constraints around what is supported by the implementation.

Methods and usage examples are documented in src/cisco_gnmi/xe.py.

XRClient

XRClient inherits from Client and provides several wrapper methods which aid with IOS XR gNMI implementation usage. These are delete_xpaths, get_xpaths, set_json, and subscribe_xpaths. These methods have some helpers and constraints around what is supported by the implementation.

Methods and usage examples are documented in src/cisco_gnmi/xr.py.

gNMI

gRPC Network Management Interface (gNMI) is a service defining an interface for a network management system (NMS) to interact with a network element. It may be thought of as akin to NETCONF or other control protocols which define operations and behaviors. The scope of gNMI is relatively simple - it seeks to "[define] a gRPC-based protocol for the modification and retrieval of configuration from a target device, as well as the control and generation of telemetry streams from a target device to a data collection system. The intention is that a single gRPC service definition can cover both configuration and telemetry - allowing a single implementation on the target, as well as a single NMS element to interact with the device via telemetry and configuration RPCs".

gNMI is a specification developed by OpenConfig, an operator-driven working-group. It is important to note that gNMI only defines a protocol of behavior - not data models. This is akin to SNMP/MIBs and NETCONF/YANG. SNMP and NETCONF are respectively decoupled from the data itself in MIBs and YANG modules. gNMI is a control protocol, not a standardization of data. OpenConfig does develop standard data models as well, and does have some specialized behavior with OpenConfig originating models, but the data models themselves are out of the scope of gNMI.

Development

Requires Python and utilizes pipenv for environment management. Manual usage of pip/virtualenv is not covered. Uses black for code formatting and pylint for code linting. black is not explicitly installed as it requires Python 3.6+.

Get Source

git clone https://github.com/cisco-ie/cisco-gnmi-python.git
cd cisco-gnmi-python
# If pipenv not installed, install!
pip install --user pipenv
# Now use Makefile...
make setup
# Or pipenv manually if make not present
pipenv --three install --dev
# Enter virtual environment
pipenv shell
# Work work
exit

Code Hygiene

We use black for code formatting and pylint for code linting. hygiene.sh will run black against all of the code under gnmi/ except for protoc compiled protobufs, and run pylint against Python files directly under gnmi/. They don't totally agree, so we're not looking for perfection here. black is not automatically installed due to requiring Python 3.6+. hygiene.sh will check for regular path availability and via pipenv, and otherwise falls directly to pylint. If black usage is desired, please install it into pipenv if using Python 3.6+ or separate methods e.g. brew install black.

# If using Python 3.6+
pipenv install --dev black
# Otherwise...
./hygiene.sh

Recompile Protobufs

If a new gnmi.proto definition is released, use update_protos.sh to recompile. If breaking changes are introduced the wrapper library must be updated.

./update_protos.sh

Licensing

cisco-gnmi-python is licensed as Apache License, Version 2.0.

Issues

Open an issue :)

Related Projects

  1. openconfig/gnmi
  2. google/gnxi
  3. Telegraf Cisco gNMI Plugin

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