Merge pull request kubernetes#24231 from mikebrow/design-docs-80col-u…

…pdates Automatic merge from submit-queue Cleans up line wrap at 80 cols and some minor editing issues Address line wrap issue kubernetes#1488. Also cleans up other minor editing issues in the docs/design/* tree such as spelling errors. Signed-off-by: mikebrow <brownwm@us.ibm.com>
bwreilly · Apr 28, 2016 · 97f1f59 · 97f1f59
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diff --git a/docs/design/README.md b/docs/design/README.md
@@ -34,19 +34,59 @@ Documentation for other releases can be found at
 
 # Kubernetes Design Overview
 
-Kubernetes is a system for managing containerized applications across multiple hosts, providing basic mechanisms for deployment, maintenance, and scaling of applications.
-
-Kubernetes establishes robust declarative primitives for maintaining the desired state requested by the user. We see these primitives as the main value added by Kubernetes. Self-healing mechanisms, such as auto-restarting, re-scheduling, and replicating containers require active controllers, not just imperative orchestration.
-
-Kubernetes is primarily targeted at applications composed of multiple containers, such as elastic, distributed micro-services. It is also designed to facilitate migration of non-containerized application stacks to Kubernetes. It therefore includes abstractions for grouping containers in both loosely coupled and tightly coupled formations, and provides ways for containers to find and communicate with each other in relatively familiar ways.
-
-Kubernetes enables users to ask a cluster to run a set of containers. The system automatically chooses hosts to run those containers on. While Kubernetes's scheduler is currently very simple, we expect it to grow in sophistication over time. Scheduling is a policy-rich, topology-aware, workload-specific function that significantly impacts availability, performance, and capacity. The scheduler needs to take into account individual and collective resource requirements, quality of service requirements, hardware/software/policy constraints, affinity and anti-affinity specifications, data locality, inter-workload interference, deadlines, and so on. Workload-specific requirements will be exposed through the API as necessary.
-
-Kubernetes is intended to run on a number of cloud providers, as well as on physical hosts.
-
-A single Kubernetes cluster is not intended to span multiple availability zones. Instead, we recommend building a higher-level layer to replicate complete deployments of highly available applications across multiple zones (see [the multi-cluster doc](../admin/multi-cluster.md) and [cluster federation proposal](../proposals/federation.md) for more details).
-
-Finally, Kubernetes aspires to be an extensible, pluggable, building-block OSS platform and toolkit. Therefore, architecturally, we want Kubernetes to be built as a collection of pluggable components and layers, with the ability to use alternative schedulers, controllers, storage systems, and distribution mechanisms, and we're evolving its current code in that direction. Furthermore, we want others to be able to extend Kubernetes functionality, such as with higher-level PaaS functionality or multi-cluster layers, without modification of core Kubernetes source. Therefore, its API isn't just (or even necessarily mainly) targeted at end users, but at tool and extension developers. Its APIs are intended to serve as the foundation for an open ecosystem of tools, automation systems, and higher-level API layers. Consequently, there are no "internal" inter-component APIs. All APIs are visible and available, including the APIs used by the scheduler, the node controller, the replication-controller manager, Kubelet's API, etc. There's no glass to break -- in order to handle more complex use cases, one can just access the lower-level APIs in a fully transparent, composable manner.
+Kubernetes is a system for managing containerized applications across multiple
+hosts, providing basic mechanisms for deployment, maintenance, and scaling of
+applications.
+
+Kubernetes establishes robust declarative primitives for maintaining the desired
+state requested by the user. We see these primitives as the main value added by
+Kubernetes. Self-healing mechanisms, such as auto-restarting, re-scheduling, and
+replicating containers require active controllers, not just imperative
+orchestration.
+
+Kubernetes is primarily targeted at applications composed of multiple
+containers, such as elastic, distributed micro-services. It is also designed to
+facilitate migration of non-containerized application stacks to Kubernetes. It
+therefore includes abstractions for grouping containers in both loosely coupled
+and tightly coupled formations, and provides ways for containers to find and
+communicate with each other in relatively familiar ways.
+
+Kubernetes enables users to ask a cluster to run a set of containers. The system
+automatically chooses hosts to run those containers on. While Kubernetes's
+scheduler is currently very simple, we expect it to grow in sophistication over
+time. Scheduling is a policy-rich, topology-aware, workload-specific function
+that significantly impacts availability, performance, and capacity. The
+scheduler needs to take into account individual and collective resource
+requirements, quality of service requirements, hardware/software/policy
+constraints, affinity and anti-affinity specifications, data locality,
+inter-workload interference, deadlines, and so on. Workload-specific
+requirements will be exposed through the API as necessary.
+
+Kubernetes is intended to run on a number of cloud providers, as well as on
+physical hosts.
+
+A single Kubernetes cluster is not intended to span multiple availability zones.
+Instead, we recommend building a higher-level layer to replicate complete
+deployments of highly available applications across multiple zones (see
+[the multi-cluster doc](../admin/multi-cluster.md) and [cluster federation proposal](../proposals/federation.md)
+for more details).
+
+Finally, Kubernetes aspires to be an extensible, pluggable, building-block OSS
+platform and toolkit. Therefore, architecturally, we want Kubernetes to be built
+as a collection of pluggable components and layers, with the ability to use
+alternative schedulers, controllers, storage systems, and distribution
+mechanisms, and we're evolving its current code in that direction. Furthermore,
+we want others to be able to extend Kubernetes functionality, such as with
+higher-level PaaS functionality or multi-cluster layers, without modification of
+core Kubernetes source. Therefore, its API isn't just (or even necessarily
+mainly) targeted at end users, but at tool and extension developers. Its APIs
+are intended to serve as the foundation for an open ecosystem of tools,
+automation systems, and higher-level API layers. Consequently, there are no
+"internal" inter-component APIs. All APIs are visible and available, including
+the APIs used by the scheduler, the node controller, the replication-controller
+manager, Kubelet's API, etc. There's no glass to break -- in order to handle
+more complex use cases, one can just access the lower-level APIs in a fully
+transparent, composable manner.
 
 For more about the Kubernetes architecture, see [architecture](architecture.md).