[WEB][42108] Kubernetes deployment: Replicas number limitation

[JulienBertrand]

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Sustainable Kubernetes deployment: Replicas number limitation

Platform

OS	OS version	Langage
-	-	Kubernetes (yaml)

Main caracteristics

ID	Title	Category	Sub-category
CRKUB003	limit replicas number	Deployment	Sustainable deploy

Severity / Remediation Cost

Severity	Remediation Cost
Minor	Minor

Rule short description

In a Kubernetes deployment file, define a high replicas number is useless and consume unnecessary resources at startup.

Rule complete description

Text

In Kubernetes configuration, the desired replicas number at start can be defined in a yaml file.
Use a high number of replicas at start might not be a good idea because it will consumes unnecessary resources.
It is better to configure an horizontal pod autoscaling.

the value is define like this:

• spec.replicas

HTML

<p>Defining the yaml file
    <code>---
      apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
  labels:
    app: nginx
spec:
  replicas: 3
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: nginx:1.7.9
        ports:
        - containerPort: 80</code> as example to perform a deployment.</p>
<p>Limit replicas number <code>replicas: x</code> to less than 3 and use horizontal pod autoscaling</p>
<h2>Noncompliant Code Example</h2>
<pre>
    <code>apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
  labels:
    app: nginx
spec:
  replicas: 8</code>
</pre>
<h2>Compliant Solution</h2>
<pre>
    <code>apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
  labels:
    app: nginx
spec:
  replicas: 2</code>
</pre>

Implementation principle

• Inspect yaml file and find 'kind: Deployment'
• Inspect the found file and find 'replicas: x'
• Compare the replicas number to the limit
• If the found value is above the limit, report the line