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32 lines
1.9 KiB
32 lines
1.9 KiB
Terminology |
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=========== |
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A few definitions before we dive into the main architecture documentation. Some of the definitions |
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are slightly contentious within the industry, however they are how Envoy uses them throughout the |
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documentation and codebase, so *c'est la vie*. |
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**Host**: An entity capable of network communication (application on a mobile phone, server, etc.). |
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In this documentation a host is a logical network application. A physical piece of hardware could |
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possibly have multiple hosts running on it as long as each of them can be independently addressed. |
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**Downstream**: A downstream host connects to Envoy, sends requests, and receives responses. |
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**Upstream**: An upstream host receives connections and requests from Envoy and returns responses. |
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**Listener**: A listener is a named network location (e.g., port, unix domain socket, etc.) that can |
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be connected to by downstream clients. Envoy exposes one or more listeners that downstream hosts |
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connect to. |
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**Cluster**: A cluster is a group of logically similar upstream hosts that Envoy connects to. Envoy |
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discovers the members of a cluster via :ref:`service discovery <arch_overview_service_discovery>`. |
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It optionally determines the health of cluster members via :ref:`active health checking |
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<arch_overview_health_checking>`. The cluster member that Envoy routes a request to is determined |
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by the :ref:`load balancing policy <arch_overview_load_balancing>`. |
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**Mesh**: A group of hosts that coordinate to provide a consistent network topology. In this |
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documentation, an “Envoy mesh” is a group of Envoy proxies that form a message passing substrate for |
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a distributed system comprised of many different services and application platforms. |
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**Runtime configuration**: Out of band realtime configuration system deployed alongside Envoy. |
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Configuration settings can be altered that will affect operation without needing to restart Envoy or |
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change the primary configuration.
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