ephemera

README

ephemerad

Ephemerad is the service that will listen on the bus and run the ephemeral scripts. This service is used in conjunction with the existing VCI tools to generate the illusion that all the components are persistent and running on the bus. It does this by acting as a proxy for VCI requests.

Component definitions

Ephemeral components are special in the eyes of the VCI helpers so their component definitions are slightly different than normal components. For ephemeral components one does not specify ExecName but instead says 'Ephemeral=true'. An example is included below.

[Vyatta Component]
Name=net.vyatta.eng.vci.example.ephemeral.toaster
Description=Ephemeral version of the VCI Toaster
Ephemeral=true
ConfigFile=/etc/toaster.conf

[Model net.vyatta.eng.vci.example.ephemeral.toaster.v1]
Modules=toaster
ModelSets=vyatta-v1

Instance definitions

Ephemerad needs to know what script to call when performing an action for the component. For this we use an instance definition such as the one below. Instance definitions are expected to be installed in the '/lib/vci/ephemera/instances' directory.

[Component]
Name=net.vyatta.eng.vci.example.ephemeral.toaster
Start=/lib/vci-toaster-ephemeral --action=start
Stop=/lib/vci-toaster-ephemeral --action=stop

[Model net.vyatta.eng.vci.example.ephemeral.toaster.v1]
Config/Check=/lib/vci-toaster-ephemeral/vci-toaster --action=validate
Config/Set=/lib/vci-toaster-ephemeral/vci-toaster --action=commit
Config/Get=/lib/vci-toaster-ephemeral/vci-toaster --action=get-config
State/Get=/lib/vci-toaster-ephemeral/vci-toaster --action=get-state
RPC/toaster/make-toast=/lib/vci-toaster-ephemeral/vci-toaster --action=make-toast
RPC/toaster/cancel-toast=/lib/vci-toaster-ephemeral/vci-toaster --action=cancel-toast
RPC/toaster/restock-toaster=/lib/vci-toaster-ephemeral/vci-toaster --action=restock-toaster

This instance definition tells ephemerad how to call the scripts when bus actions are called. There is one instance definition per managed component. The instance definitions are installed in '/lib/vci/ephemera/instances'.

The script environement

Scripts are called using the UNIX environment and standard interfaces for interaction. The environment will be setup as follows.

UNIX interface	Function
stdin	The rfc7951 encoded data for the action (if any).
stdout	The rfc7951 encoded output for the action (if any).
stderr	Error output from the action, may be rfc7951 encoded YANG messages or strings.
VCI_COMPONENT_NAME	Name of the component.
VCI_MODEL_NAME	Name of the model.
VCI_RPC_METADATA	The json encoded metadata associated with an RPC call.
EPHEMERA_MESSAGE	The statement from the instance file that is being invoked. 'Config/Get', 'RPC/module/name', etc.
exit code	Determins whether the script had an error (0 success; non-0 failure)

Conclusion

Ephemeral components allow for hopefully an easier transition for certain features to VCI. The ephemeral components will use considerably less resident memory than a full fledged component and are appropriate for small features.

Documentation

Overview

Copyright (c) 2019-2021, AT&T Intellectual Property. All rights reseved.

SPDX-License-Identifier: GPL-2.0-only

Index

• type Component
  • func New(opts ...Opt) (*Component, error)
  • func (c *Component) Equal(other interface{}) bool
  • func (c *Component) Models() map[string]*Model
  • func (c *Component) Name() string
  • func (c *Component) Start() error
  • func (c *Component) Stop() error
• type Model
  • func (c *Model) Config() (interface{}, bool)
  • func (c *Model) Equal(other interface{}) bool
  • func (c *Model) RPC() (map[string]map[string]interface{}, bool)
  • func (c *Model) State() (interface{}, bool)
• type Opt
  • func From(file string) Opt

Types

type Component

type Component struct {
	// contains filtered or unexported fields
}

func New

func New(opts ...Opt) (*Component, error)

func (*Component) Equal

func (c *Component) Equal(other interface{}) bool

func (*Component) Models

func (c *Component) Models() map[string]*Model

func (*Component) Name

func (c *Component) Name() string

func (*Component) Start

func (c *Component) Start() error

func (*Component) Stop

func (c *Component) Stop() error

type Model

type Model struct {
	// contains filtered or unexported fields
}

func (*Model) Config

func (c *Model) Config() (interface{}, bool)

func (*Model) Equal

func (c *Model) Equal(other interface{}) bool

func (*Model) RPC

func (c *Model) RPC() (map[string]map[string]interface{}, bool)

func (*Model) State

func (c *Model) State() (interface{}, bool)

type Opt

type Opt func(*Component)

func From

func From(file string) Opt