[Kubernetes Resources] Detailed Explanation of Namespace Namespace

1. Namespace concept

K8s Chinese manual:

K8s namespace Chinese official manual:

Kubernetes supports multiple virtual clusters that rely on the same physical cluster underlying them. These virtual clusters are called namespaces.
The namespace namespace is a resource at the k8s cluster level, which can create corresponding namespaces for different users, tenants, environments or projects.

In Kubernetes, namespaces can be used to:

• Isolate different applications to avoid naming conflicts and resource competition. -
• Provide separate environments for different teams or projects so they can manage and deploy applications independently.
• Control resource quotas and access permissions to ensure secure isolation between applications.

Namespace can be abstractly understood as, QQ group, there are different friends in the group, friends are containers.

2. Basic operation of namespace

1. Two ways to create Namespace

There are two ways to create a namespace, through the command line and YAML file, as follows:

The first method: create a Namespace through the command line entry

kubectl create ns mytest

The second method: Create a Namespace through the YAML resource list

cat namespace.yaml 

---
apiVersion: v1
kind: Namespace
metadata:
  name: mytest

Created by apply

kubectl apply -f namespace.yaml

view namespace

kubectl get ns
kubectl get ns mytest

2. Namespace resource limit

You can use Resource Quota to limit the use of resources in the Namespace. Resource quotas are a control mechanism that can limit the use of resources in the Namespace, including CPU, memory, and storage.

Resource limits can be limited for all Pods in the Namespace, or for a single Pod:

cat resourcequota.yaml 
apiVersion: v1
kind: Namespace
metadata:
  name: mytest
---
apiVersion: v1
kind: ResourceQuota
metadata:
  name: mytest-quota
  namespace: mytest
spec:
  hard:
    requests.cpu: 2
    requests.memory: 2Gi
    limits.cpu: 4
    limits.memory: 4Gi

Explanation of configuration meaning:

Resource Name	describe
limits.cpu	The total CPU quota of all non-terminal Pods cannot exceed this value.
limits.memory	The total memory quota of all non-terminal Pods cannot exceed this value.
requests.cpu	The total CPU demand of all non-terminal Pods cannot exceed this value.
requests.memory	The total memory requirements of all non-terminal Pods cannot exceed this value.
hugepages-<size>	The total number of huge page requests for the specified size cannot exceed this value for all non-terminating pods.
cpu	Same as requests.cpu.
memory	Same as requests.memory.

Execute the apply file

kubectl apply -f resourcequota.yaml

View Resource Quota information:

kubectl get resourcequota -n mytest

Test: Create a Pod and limit resource usage as follows:

Note: If the Namespace has resource quotas, then resources must be used to limit when creating Pods.

cat pod.yaml 
---
apiVersion: v1
kind: Pod
metadata:
  labels:
    app: nginx
  name: web-nginx
  namespace: mytest
spec:
  containers:
  - name: web-nginx
    image: nginx
    imagePullPolicy: IfNotPresent
    ports:
    - containerPort: 80 
    resources:
      limits:
        memory: "2Gi"
        cpu: "2"
      requests:
        memory: "1000Mi"
        cpu: "500m"

View resourcequota resource limit information:

kubectl get resourcequota -n mytest

If the namespace quota limit is exceeded, an error will be reported, as shown in the figure below: