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Glossary

Tendrl Project

Tendrl

Umbrella project that houses all the Stacks.

Stack

Stack is a group of sub-projects that together enable a specific set of functionalities in a Tendrl deployment. Stacks may be composed of one or more sub-projects and/or infrastructure components.

Sub-project

An individual codebase housed under the Tendrl project.

Tendrl Core

The standalone, self-sufficient Stack that implements the core management, provisioning and monitoring functionality supported by Tendrl and exposes it over an API.

Tendrl UI

A Stack that provides a graphical user interface to the administrator. UI Stack leverages the functionality provided by the Tendrl Core Stack via it’s API.

Tendrl Core Components

Node

A host which can be used as part of a Storage System cluster.

Storage Node

Same as Node.

App

Tendrl API Application.

API

HTTP interface exposed by the App.

Central Store

Central datastore that is the single repository of all the data in a Tendrl Core deployment.

Agent

Component that enables Tendrl Core to manage a Node.

Node Agent

Same as Agent.

Bridge

Component that implements a Storage System specific interface.

Software Defined Storage (SDS) Bridge

Same as Bridge.

Tendrl Core Concepts

State

Representation of the Storage System in the Central Store. State includes all the relevant information necessary for the App to manage and monitor the Storage System. State is comprised of Objects. State is represented in the Central Store via a hierarchy of keys and values organised with directories.

State Representation

Same as State.

State Definition

A YAML file that describes the various parts of the State Representation to the App.

State Bridge

Part of the Bridge that is specifically responsible for gathering and maintaining the Storage System State in the Central Store.

Object

Object is any entity from the State representation that is of relevance to the App. Objects are made known to the App via the State Definition.

Object State

Every Object can be in a specific state at any given point in time. Valid Object States and allowed Actions on each of the States are made known to the App via the State Definition.

Attribute

Properties of the Object that the App needs to know about. Attributes have a location (within the State Representation) and a datatype and are made known to the App via the State Definition.

Action

Action is a method that can be invoked against a specific Object. Actions can have Parameters. Actions and the associated Parameters are made known to the App via the State Definition.

Parameter

Parameters are associated with specific Actions. They have a defined datatype and the associated validation.

Operation

Operation is an Action that is:

  • either invoked against more than one Object.

  • or comprises of more than one Action. Operation can be comprised of multiple Steps. Steps encapsulate Actions. Operation’s flow is determined based on the outcome of individual Steps that get executed in the sequence defined by the Operation. Depending upon the Steps, an Operation could be transactional.

Step

A Step in an Operation is an atomic grouping of Actions. Step can be a single Action as well. Within a single Operation, Steps can have dependencies and depending upon the outcome of a single Step the rest of the Steps may or may not be executed.