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Merge pull request #9137 from RichieEscarez/8701_repctr2

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Added inline  links to "services" "pods" "namespaces" "secrets"  and …
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Quinton Hoole
2015-06-05 09:33:00 -07:00
parent 4a7f3cc2fa 320bc1ce4b
commit a55c652466
3 changed files with 10 additions and 10 deletions
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8
examples/hazelcast/README.md
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@@ -4,7 +4,7 @@ The following document describes the development of a _cloud native_ [Hazelcast]
Any topology changes are communicated and handled by Hazelcast nodes themselves.
This document also attempts to describe the core components of Kubernetes, _Pods_, _Services_ and _Replication Controllers_.
This document also attempts to describe the core components of Kubernetes: _Pods_, _Services_, and _Replication Controllers_.
### Prerequisites
This example assumes that you have a Kubernetes cluster installed and running, and that you have installed the `kubectl` command line tool somewhere in your path. Please see the [getting started](https://github.com/GoogleCloudPlatform/kubernetes/tree/master/docs/getting-started-guides) for installation instructions for your platform.
@@ -20,13 +20,13 @@ Source is freely available at:
* Docker Trusted Build - https://registry.hub.docker.com/u/pires/hazelcast-k8s
### Simple Single Pod Hazelcast Node
In Kubernetes, the atomic unit of an application is a [_Pod_](http://docs.k8s.io/pods.md). A Pod is one or more containers that _must_ be scheduled onto the same host. All containers in a pod share a network namespace, and may optionally share mounted volumes.
In Kubernetes, the atomic unit of an application is a [_Pod_](../../docs/pods.md). A Pod is one or more containers that _must_ be scheduled onto the same host. All containers in a pod share a network namespace, and may optionally share mounted volumes.
In this case, we shall not run a single Hazelcast pod, because the discovery mechanism now relies on a service definition.
### Adding a Hazelcast Service
In Kubernetes a _Service_ describes a set of Pods that perform the same task. For example, the set of nodes in a Hazelcast cluster. An important use for a Service is to create a load balancer which distributes traffic across members of the set. But a _Service_ can also be used as a standing query which makes a dynamically changing set of Pods available via the Kubernetes API. This is actually how our discovery mechanism works, by relying on the service to discover other Hazelcast pods.
In Kubernetes a _[Service](../../docs/services.md)_ describes a set of Pods that perform the same task. For example, the set of nodes in a Hazelcast cluster. An important use for a Service is to create a load balancer which distributes traffic across members of the set. But a _Service_ can also be used as a standing query which makes a dynamically changing set of Pods available via the Kubernetes API. This is actually how our discovery mechanism works, by relying on the service to discover other Hazelcast pods.
Here is the service description:
```yaml
@@ -54,7 +54,7 @@ $ kubectl create -f hazelcast-service.yaml
### Adding replicated nodes
The real power of Kubernetes and Hazelcast lies in easily building a replicated, resizable Hazelcast cluster.
In Kubernetes a _Replication Controller_ is responsible for replicating sets of identical pods. Like a _Service_ it has a selector query which identifies the members of it's set. Unlike a _Service_ it also has a desired number of replicas, and it will create or delete _Pods_ to ensure that the number of _Pods_ matches up with it's desired state.
In Kubernetes a _[Replication Controller](../../docs/replication-controller.md)_ is responsible for replicating sets of identical pods. Like a _Service_ it has a selector query which identifies the members of it's set. Unlike a _Service_ it also has a desired number of replicas, and it will create or delete _Pods_ to ensure that the number of _Pods_ matches up with it's desired state.
Replication Controllers will "adopt" existing pods that match their selector query, so let's create a Replication Controller with a single replica to adopt our existing Hazelcast Pod.