EOS Designs internal notes

Warning

Anything mentioned here is subject to change without notice. Use of avd_switch_facts in custom templates is not supported and should be avoided.

Overview

flowchart TD
  subgraph role[arista.avd.eos_designs role]
    eos_designs_facts[[arista.avd.eos_designs_facts action plugin]] -->
    eos_designs_structured_config[[arista.avd.eos_designs_structured_config action plugin]]-->
    RemoveAvdSwitchFacts(Remove AvdSwitchFacts)
  end

Ansible Action Plugins

arista.avd.eos_designs_facts

The arista.avd.eos_designs_facts module is an Ansible Action Plugin providing the following capabilities:

• Set avd_switch_facts fact containing internal AVD facts per switch.

The plugin is designed to run_once. With this, Ansible will set the same facts on all devices, so all devices can lookup values of any other device without using the slower hostvars.

The module is used in arista.avd.eos_designs to set facts for devices, which are then used by Python modules loaded in arista.avd.eos_designs_structured_config to generate the structured_configuration.

Arguments

  template_output: <true | false | default -> false>
  validation_mode: <"error" | "warning" | default -> "error">
  cprofile_file: <Filename for storing cprofile data used to debug performance issues>

See the full argument spec here

Output data model

ansible_facts:
  avd_switch_facts:
    <switch_1>: < dict with internal AVD facts used within eos_designs >
    <switch_2>: ...

The facts for each device follows the schema described here.

The facts can be inspected in a file per device by running the arista.avd.eos_designs role with -e avd_eos_designs_debug="{{ true }}".

Internal structure

classDiagram
  direction LR
  class eos_designs_facts{
    - Verify devices are in one fabric group
    - Read and template default role_vars
    - Read and validate Hostvars for all devices
    - Instantiate SharedUtils and EosDesignsFacts classes per device
    - Set "avd_switch_facts" referencing all EosDesignsFacts instances
    - Run "render" method on all EosDesignsFacts instances
    - Build facts from data returned by "render"
  }
  class ActionBase{
  }
  class AvdSchemaTools{
  }
  class EosDesignsFacts{
    avd_switch_facts: dict[str, EosDesignsFacts]
    render(): dict
  }
  ActionBase <|-- eos_designs_facts : extends
  eos_designs_facts --* AvdSchemaTools
  eos_designs_facts --* "many" EosDesignsFacts : per device
  EosDesignsFacts ..> eos_designs_facts : pointer to instances for other devices

arista.avd.eos_designs_structured_config

TODO

Python packages

AvdFacts

The AvdFacts class serve as a base class for EosDesignsFacts as well as the many AvdStructuredConfig* classes.

The purpose of AvdFacts subclasses is to return a dictionary when the render method is called.

The class is also partially emulating a dict type by exposing keys() and get() methods and exposing all public attributes as cached_property. This allows for a class instance to be used as part of a deeper data model, where our utility tools can traverse deeper data models using dot-notation. It also allows for partial rendering of data, since only the accessed attributes/cached_properties will be rendered.

The base class has a few important methods:

• keys() return a list of attributes not beginning with an underscore and where the attribute is decorated with cached_property. These attributes represent the keys in the emulated dict.
• render() loop over every attribute returned by keys() and return a dict with all the returned cached_properties, except cached_property with a value of None which will be skipped.
• get(key, default=None) returns the value of the requested “key” (cached_property) if the “key” is in the list returned by keys(). Otherwise the default value is returned.

See the source code here

get_structured_config

TODO

EosDesignsFacts

EosDesignsFacts is based on AvdFacts, so make sure to read the description there first.

The class is instantiated once per device. Methods may use references to other device instances using hostvars.avd_switch_facts, which is a dict of EosDesignsfacts instances covering all devices.

See the source code here

classDiagram
  direction LR
  class AvdFacts{
    render(): dict
  }
  class EosDesignsFacts{
    shared_utils: SharedUtils
    _hostvars: dict
  }
  class MlagMixin
  class OverlayMixin
  class ShortEsiMixin
  class UplinksMixin
  class VlansMixin
  class SharedUtils
  AvdFacts <|-- EosDesignsFacts : extends
  MlagMixin <|-- EosDesignsFacts : extends
  OverlayMixin <|-- EosDesignsFacts : extends
  ShortEsiMixin <|-- EosDesignsFacts : extends
  UplinksMixin <|-- EosDesignsFacts : extends
  VlansMixin <|-- EosDesignsFacts : extends
  EosDesignsFacts --* SharedUtils
  SharedUtils ..> EosDesignsFacts

SharedUtils

See the source code here

classDiagram
  direction LR
  class InterfaceDescriptionsMixin
  class BgpPeerGroupsMixin
  class LinkTrackingGroupsMixin
  class MgmtMixin
  class MlagMixin
  class MiscMixin
  class NodeTypeKeyMixin
  class OverlayMixin
  class PlatformMixin
  class PtpMixin
  class SwitchDataMixin
  class RoutingMixin
  class UnderlayMixin
  class UtilsMixin
  class IpAddressingMixin
  InterfaceDescriptionsMixin --* AvdInterfaceDescriptions
  InterfaceDescriptionsMixin <|-- SharedUtils : extends
  BgpPeerGroupsMixin <|-- SharedUtils : extends
  LinkTrackingGroupsMixin <|-- SharedUtils : extends
  MgmtMixin <|-- SharedUtils : extends
  MlagMixin <|-- SharedUtils : extends
  MiscMixin <|-- SharedUtils : extends
  NodeTypeKeyMixin <|-- SharedUtils : extends
  OverlayMixin <|-- SharedUtils : extends
  PlatformMixin <|-- SharedUtils : extends
  PtpMixin <|-- SharedUtils : extends
  SwitchDataMixin <|-- SharedUtils : extends
  RoutingMixin <|-- SharedUtils : extends
  UnderlayMixin <|-- SharedUtils : extends
  UtilsMixin <|-- SharedUtils : extends
  IpAddressingMixin <|-- SharedUtils : extends
  IpAddressingMixin --* AvdIpAddressing

AvdStructuredConfig*

AvdStructuredConfig* classes are based on AvdFacts, so make sure to read the description there first.

The generation of the final structured_config is split into multiple python modules which are subclasses of AvdFacts. Each class is loaded in get_structured_config and rendered. All the results are deepmerged into the final structured_config.

The class is instantiated once per device. Methods may use references to other device instances using hostvars.avd_switch_facts, which at the time where eos_designs_structured_config run, is a nested dict. It contains the output from EosDesignsFacts’s render() method.

Subclasses are typically using Mixin classes to split all the attributes/cached_properties into manageable files.

See the source code here

classDiagram
  direction LR
  class AvdFacts{
    render(): dict
  }
  class AvdStructuredConfigBase
  class AvdStructuredConfigConnectedEndpoints
  class AvdStructuredConfigCoreInterfacesAndL3Edge
  class AvdStructuredConfigCustomStructuredConfiguration
  class AvdStructuredConfigInbandManagement
  class AvdStructuredConfigMlag
  class AvdStructuredConfigNetworkServices
  class AvdStructuredConfigOverlay
  class AvdStructuredConfigUnderlay
  AvdFacts <|-- AvdStructuredConfigBase : extends
  AvdFacts <|-- AvdStructuredConfigConnectedEndpoints : extends
  AvdFacts <|-- AvdStructuredConfigCoreInterfacesAndL3Edge : extends
  AvdFacts <|-- AvdStructuredConfigCustomStructuredConfiguration : extends
  AvdFacts <|-- AvdStructuredConfigInbandManagement : extends
  AvdFacts <|-- AvdStructuredConfigMlag : extends
  AvdFacts <|-- AvdStructuredConfigNetworkServices : extends
  AvdFacts <|-- AvdStructuredConfigOverlay : extends
  AvdFacts <|-- AvdStructuredConfigUnderlay : extends
  AvdStructuredConfigBase --* SharedUtils
  AvdStructuredConfigConnectedEndpoints --* SharedUtils
  AvdStructuredConfigCoreInterfacesAndL3Edge --* SharedUtils
  AvdStructuredConfigCustomStructuredConfiguration --* SharedUtils
  AvdStructuredConfigInbandManagement --* SharedUtils
  AvdStructuredConfigMlag --* SharedUtils
  AvdStructuredConfigNetworkServices --* SharedUtils
  AvdStructuredConfigOverlay --* SharedUtils
  AvdStructuredConfigUnderlay --* SharedUtils

Facts set at runtime

avd_switch_facts

The following model is set as eos_designs_facts. Most keys are optional depending on the use case and configuration.