Adding initial glossary of terms
Along with defining terms, this commit cleans up some of the documentation structure so the auto-generated docs are a bit cleaner. Change-Id: I6445f86a6746956d8227d2a587509fe08b27d26d
This commit is contained in:
Stephen Balukoff
parent
33859efeb5
commit
ef836fca84
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@ -68,7 +68,7 @@ copyright = u'2014, OpenStack Octavia Team'
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# List of patterns, relative to source directory, that match files and
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# directories to ignore when looking for source files.
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exclude_patterns = ['_build']
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exclude_patterns = ['_build', 'specs/skeleton.rst', 'specs/template.rst']
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# The reST default role (used for this markup: `text`) to use for all documents.
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#default_role = None
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@ -1,16 +1,18 @@
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.. octavia-specs documentation master file
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==============================
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Octavia Project Specifications
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==============================
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Contents:
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====
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Main
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====
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.. toctree::
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:glob:
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:maxdepth: 1
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specs/*
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main/*
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======================
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Project Specifications
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======================
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Version 0.5 specs:
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@ -20,7 +22,7 @@ Version 0.5 specs:
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specs/version0.5/*
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Version 1 specs:
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Version 1:
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.. toctree::
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:glob:
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@ -28,9 +30,9 @@ Version 1 specs:
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specs/version1/*
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============================
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Octavia Design Documentation
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============================
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====================
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Design Documentation
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====================
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Version 0.5:
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@ -0,0 +1,163 @@
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================
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Octavia Glossary
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================
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As the Octavia project evolves, it's important that people working on Octavia,
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users using Octavia, and operators deploying Octavia use a common set of
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terminology in order to avoid misunderstandings and confusion. To that end, we
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are providing the following glossary of terms.
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Note also that many of these terms are expanded upon in design documents in
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this same repository. What follows is a brief but necessarily incomplete
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description of these terms.
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.. glossary:: :sorted:
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Amphora
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Virtual machine, container, dedicated hardware, appliance or device
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that actually performs the task of load balancing in the Octavia
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system. More specifically, an amphora takes requests from clients on
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the front-end and distributes these to back-end systems. Amphorae
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communicate with their controllers over the LB Network through a driver
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interface on the controller.
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Amphora Load Balancer Driver
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Component of the controller that does all the communication with
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amphorae. Drivers communicate with the controller through a generic
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base class and associated methods, and translate these into control
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commands appropriate for whatever type of software is running on the
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back-end amphora corresponding with the driver. This communication
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happens over the LB network.
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Apolocation
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Term used to describe when two or more amphorae are not colocated on
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the same physical hardware (which is often essential in HA topologies).
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May also be used to describe two or more loadbalancers which are not
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colocated on the same amphora.
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Controller
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Daemon with access to both the LB Network and OpenStack components
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which coordinates and manages the overall activity of the Octavia load
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balancing system. Controllers will usually use an abstracted driver
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interface (usually a base class) for communicating with various other
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components in the OpenStack environment in order to facilitate loose
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coupling with these other components. These are the "brains" of the
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Octavia system.
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HAProxy
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Load balancing software used in the reference implementation for
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Octavia. (See http://www.haproxy.org/ ). HAProxy processes run on
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amphorae and actually accomplish the task of delivering the load
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balancing service.
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Health Monitor
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An object that defines a check method for each member of the pool.
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The health monitor itself is a pure-db object which describes the
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method the load balancing software on the amphora should use to
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monitor the health of back-end members of the pool with which the
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health monitor is associated.
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L7 Policy
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Layer 7 Policy
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Collection of L7 rules that get logically ANDed together as well as a
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routing policy for any given HTTP or terminated HTTPS client requests
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which match said rules. An L7 Policy is associated with exactly one
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HTTP or terminated HTTPS listener.
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For example, a user could specify an L7 policy that any client request
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that matches the L7 rule "request URI starts with '/api'" should
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get routed to the "api" pool.
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L7 Rule
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Layer 7 Rule
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Single logical expression used to match a condition present in a given
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HTTP or terminated HTTPS request. L7 rules typically match against
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a specific header or part of the URI and are used in conjuncion with
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L7 policies to accomplish L7 switching. An L7 rule is associated with
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exactly one L7 policy.
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For example, a user could specify an L7 rule that matches any request
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URI path that begins with "/api"
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L7 Switching
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Layer 7 Switching
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This is a load balancing feature specific to HTTP or terminated HTTPS
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sessions, in which different client requests are routed to different
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back-end pools depending on one or more layer 7 policies the user might
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configure.
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For example, using L7 switching, a user could specify that any
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requests with a URI path that starts with "/api" get routed to the
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"api" back-end pool, and that all other requests get routed to the
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default pool.
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LB Network
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Load Balancer Network. The network over which the controller(s) and
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amphorae communicate. The LB network itself will usually be a nova or
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neutron network to which both the controller and amphorae have access,
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but is not associated with any one tenant. The LB Network is generally
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also *not* part of the undercloud and should not be directly exposed to
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any OpenStack core components other than the Octavia Controller.
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Listener
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Object representing the listening endpoint of a load balanced service.
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TCP / UDP port, as well as protocol information and other protocol-
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specific details are attributes of the listener. Notably, though, the
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IP address is not.
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Load Balancer
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Object describing a logical grouping of listeners on one or more VIPs
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and associated with one or more amphorae. (Our "Loadbalancer" most
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closely resembles a Virtual IP address in other load balancing
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implementations.) Whether the load balancer exists on more than one
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amphora depends on the topology used. The load balancer is also often
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the root object used in various Octavia APIs.
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Load Balancing
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The process of taking client requests on a front-end interface and
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distributing these to a number of back-end servers according to various
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rules. Load balancing allows for many servers to participate in
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delivering some kind TCP or UDP service to clients in an effectively
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transparent and often highly-available and scalable way (from the
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client's perspective).
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Member
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Object representing a single back-end server or system that is a
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part of a pool. A member is associated with only one pool.
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Octavia
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Octavia is an operator-grade open source load balancing solution. Also
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known as the Octavia system or Octavia project. The term by itself
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should be used to refer to the system as a whole and not any
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individual component within the Octavia load balancing system.
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Pool
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Object representing the grouping of members to which the listener
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forwards client requests. Note that a pool is associated with only
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one listener, but a listener might refer to several pools (and switch
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between them using layer 7 policies).
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TLS Termination
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Transport Layer Security Termination
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Type of load balancing protocol where HTTPS sessions are terminated
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(decrypted) on the amphora as opposed to encrypted packets being
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forwarded on to back-end servers without being decrypted on the
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amphora. Also known as SSL termination. The main advantages to this
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type of load balancing are that the payload can be read and / or
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manipulated by the amphora, and that the expensive tasks of handling
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the encryption are off-loaded from the back-end servers. This is
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particularly useful if layer 7 switching is employed in the same
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listener configuration.
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VIP
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Virtual IP Address
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Single service IP address which is associated with a load balancer.
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This is similar to what is described here:
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http://en.wikipedia.org/wiki/Virtual_IP_address
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In a highly available load balancing topology in Octavia, the VIP might
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be assigned to several amphorae, and a layer-2 protocol like CARP,
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VRRP, or HSRP (or something unique to the networking infrastructure)
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might be used to maintain its availability. In layer-3 (routed)
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topologies, the VIP address might be assigned to an upstream networking
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device which routes packets to amphorae, which then load balance
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requests to back-end members.
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