Merge pull request #1140 from network-charles/network-charles-patch-2

Scheduler Testing with KWOK (Technical Outcome)

site/config.yaml

@@ -121,6 +121,12 @@ menu:
   - identifier: contributing
     pageRef: "/docs/contributing"
     weight: 30
+  # Technical Outcomes
+  - identifier: technical-outcomes
+    title: Technical Outcomes
+  - identifier: technical-outcomes-scheduling
+    pageRef: "/docs/technical-outcomes/scheduling"
+    parent: technical-outcomes
 
   # User Guide Children
   - identifier: all-in-one-image
@@ -267,6 +273,32 @@ menu:
     pageRef: "/docs/contributing/development"
     parent: contributing
 
+  # Technical Outcome Scheduling Children
+  - identifier: technical-outcomes-scheduling-requests-and-limits
+    title: "Requests and Limits"
+    pageRef: "/docs/technical-outcomes/scheduling/requests-and-limits"
+    parent: technical-outcomes-scheduling
+  - identifier: technical-outcomes-scheduling-node-affinity
+    title: "Node Affinity"
+    pageRef: "/docs/technical-outcomes/scheduling/node-affinity"
+    parent: technical-outcomes-scheduling
+  - identifier: technical-outcomes-scheduling-taints-and-tolerations
+    title: "Taints and Tolerations"
+    pageRef: "/docs/technical-outcomes/scheduling/taints-and-tolerations"
+    parent: technical-outcomes-scheduling
+  - identifier: technical-outcomes-scheduling-limit-range
+    title: "Limit Range"
+    pageRef: "/docs/technical-outcomes/scheduling/limit-range"
+    parent: technical-outcomes-scheduling
+  - identifier: technical-outcomes-scheduling-pod-priority-and-preemption
+    title: "Pod Priority and Preemption"
+    pageRef: "/docs/technical-outcomes/scheduling/pod-priority-and-preemption"
+    parent: technical-outcomes-scheduling
+  - identifier: technical-outcomes-scheduling-pod-topology-spread-constraint
+    title: "Pod Topology Spread Constraint"
+    pageRef: "/docs/technical-outcomes/scheduling/pod-topology-spread-constraint"
+    parent: technical-outcomes-scheduling
+
   after:
   - identifier: blog
     pageRef: "/posts"

site/content/en/_index.md

@@ -28,7 +28,9 @@ which means that simulating a large number of nodes and pods requires a lot of m
 
 ### What's the difference with `kind`
 
-[kind] runs Kubernetes in Docker, creating a real cluster.
+[kind] runs Kubernetes in Docker, creating a real cluster. If you deploy a nginx pod to a 
+[kind] cluster, you could curl to its IP address and get an HTTP response containing its HTML
+page. But in a KWOK cluster, you get nothing because the pod isn't real.
 
 `kwokctl` can be used as an alternative to [kind] in some scenarios where you don’t need to actually run any pod.
 

site/content/en/docs/technical-outcomes/scheduling/_index.md

@@ -0,0 +1,24 @@
+---
+title: Scheduler Testing
+---
+
+# Scheduler Testing with KWOK
+
+{{< hint "info" >}}
+
+This document walks you through the technical outcome of using KWOK for scheduler tests.
+
+{{< /hint >}}
+
+KWOK can be used to create fake nodes and pods in a simulated cluster.
+The cluster can be configured with scheduling policies that meet your scheduler's requirements.
+The scenarios below can be used to describe this:
+
+- [Scheduling pods with resource requests and limits](/docs/technical-outcomes/scheduling/requests-and-limits)
+- [Scheduling a pod to a particular node with node-affinity](/docs/technical-outcomes/scheduling/node-affinity)
+- [Scheduling pods with taints and tolerations](/docs/technical-outcomes/scheduling/taints-and-tolerations)
+- [Scheduling pods with a limit range](/docs/technical-outcomes/scheduling/limit-range)
+- [Scheduling pods using pod priority and preemption](/docs/technical-outcomes/scheduling/pod-priority-and-preemption)
+- [Scheduling pods using pod topology spread constraints](/docs/technical-outcomes/scheduling/pod-topology-spread-constraint)
+
+Other scheduling scenarios can also be simulated using KWOK.

site/content/en/docs/technical-outcomes/scheduling/limit-range/_index.md

@@ -0,0 +1,110 @@
+---
+title: "Limit Range"
+---
+
+# Scheduling pods with a limit range
+
+A limit range schedule policy can be used in a KWOK cluster.
+
+<img width="700px" src="limit-range.svg">
+
+## Prerequisites
+
+- KWOK must be installed on the machine. See [installation](https://kwok.sigs.k8s.io/docs/user/installation/).
+- Install [kubectl](https://kubernetes.io/docs/tasks/tools/install-kubectl-linux/)
+
+## Create cluster
+
+```bash
+kwokctl create cluster
+```
+
+## View clusters
+
+This ensures that the cluster was created successfully.
+
+```bash
+kwokctl get clusters
+```
+
+## Create nodes
+
+```bash
+kwokctl scale node --replicas 1
+```
+
+## Create a resource limit
+
+{{< expand "limit-range.yaml" >}}
+
+{{< code-sample file="limit-range.yaml" >}}
+
+{{< /expand >}}
+
+```bash
+kubectl apply -f limit-range.yaml
+```
+
+## Confirm the limit has the required values
+
+```bash
+kubectl describe limitranges cpu-resource-constraint
+
+Name:       cpu-resource-constraint
+Namespace:  default
+Type        Resource  Min   Max  Default Request  Default Limit  Max Limit/Request Ratio
+----        --------  ---   ---  ---------------  -------------  -----------------------
+Container   cpu       100m  1    500m             500m           -
+```
+
+## Deploy a pod above the resource limit
+
+- Pod specification:
+  - CPU Request: 700m
+
+{{< expand "pod-beyond-limit.yaml" >}}
+
+{{< code-sample file="pod-beyond-limit.yaml" >}}
+
+{{< /expand >}}
+
+```bash
+kubectl create -f pod-beyond-limit.yaml
+```
+
+Notice the error `Invalid value: "700m": must be less than or equal to cpu limit of 500m`
+
+## Deploy a pod within the resource limit
+
+- Pod specification:
+  - CPU Request: 400m
+
+{{< expand "pod-within-limit.yaml" >}}
+
+{{< code-sample file="pod-within-limit.yaml" >}}
+
+{{< /expand >}}
+
+```bash
+kubectl apply -f pod-within-limit.yaml
+```
+
+## Confirm that the pod is running
+
+```bash
+kubectl get pod
+
+NAME                 READY   STATUS    RESTARTS   AGE
+pod-within-limit   1/1     Running   0          10s
+```
+
+## Delete the cluster
+
+```bash
+kwokctl delete cluster
+```
+
+## Conclusion
+
+This example demonstrates how to use KWOK to simulate a scheduling
+scenario based on setting a [limit range](https://kubernetes.io/docs/concepts/policy/limit-range/) policy.