Terminology
This page documents the various terms used in relation to mcollective.
Server
The mcollective daemon, an app server for hosting Agents and managing the connection to your Middleware.
Node
The Computer or Operating System that the Server runs on.
Agent
A block of Ruby code that performs a specific role, the main reason for mcollective’s existence is to host agents. Agents can perform tasks like manipulate firewalls, services, packages etc. See Wikipedia.
Docs to write your own can be seen in SimpleRPCAgents
Plugins
Ruby code that lives inside the server and takes on roles like security, connection handling, agents and so forth. See Wikipedia
Middleware
A publish subscribe based system like Apache ActiveMQ.
Connector
A plugin of the type MCollective::Connector that handles the communication with your chosen Middleware.
Name Space
Currently messages are sent to the middleware directed at topics named /topic/mcollective.package.command and replies come back on /topic/mcollective.package.reply.
In this example the namespace is “mcollective” and all servers and clients who wish to form part of the same Collective must use the same name space.
Middleware can generally carry several namespaces and therefore several Collectives.
Collective
A combination of Servers, Nodes and Middleware all operating in the same Namespace.
Multiple collectives can be built sharing the same Middleware but kept separate by using different Namespaces.
Subcollective
A server can belong to many Namespaces. A Subcollective is a Namespace that only a subset of a full collectives nodes belong to.
Subcolllectives are used to partition networks and to control broadcast domains in high traffic networks.
Simple RPC
A Remote Procedure Call system built ontop of MCollective that makes it very simple to write feature full agents and clients. See SimpleRPCIntroduction.
Action
Agents expose tasks, we call these tasks actions. Each agent like a exim queue management agent might expose many tasks like mailq, rm, retry etc. These are al actions provided by an agent.
Facts
Discreet bits of information about your nodes. Examples could be the domain name, country, role, operating system release etc.
Facts are provided by plugins of the type MCollective::Facts, you can read about writing your own in WritingFactsPlugins
Registration
Servers can send regular messages to an agent called registration. The code that sends the registration messages are plugins of the type MCollective::Registration. See Registration.
Security
A plugin of the type MCollective::Security that takes care of encryption, authentication and encoding of messages on which will then be passed on to the Connector for delivery to the Collective.
Client
Software that produce commands for agents to process, typically this would be a computer with the client package installed and someone using the commands like mc-package to interact with Agents.
Often clients will use the MCollective::Client library to communicate to the Collective
User
Servers and Clients all authenticate to the Middleware, user would generally refer to the username used to authenticate against the middleware.
Audit
In relation to SimpleRPC an audit action is a step requests go through where they can get logged to disk or other similar action
Authorization
In relation to SimpleRPC authorization is a processes whereby requests get allowed or denied based on some identifying information of the requester. See SimpleRPCAuthorization.