k8s-deployment

Author: callicoder

deployments/kustomization.yaml

@@ -3,19 +3,15 @@ secretGenerator:
 - name: mysql-root-pass
   literals:
   - password=R00t
-- name: mysql-user
+- name: mysql-user-pass
   literals:
-  - username=callicoder 
-- name: mysql-pass
-  literals:
-  - password=c@ll1c0d3r
-- name: mysql-db
-  literals:
-  - database=polls      
-- name: mysql-url
+  - username=callicoder
+  - password=c@ll1c0d3r 
+- name: mysql-db-url
   literals:
+  - database=polls
   - url=jdbc:mysql://polling-app-mysql:3306/polls?useSSL=false&serverTimezone=UTC&useLegacyDatetimeCode=false
 resources:
   - mysql-deployment.yaml
   - polling-app-server.yaml
-  - polling-app-client.yaml  
+  - polling-app-client.yaml  

deployments/mysql-deployment.yaml

@@ -1,80 +1,97 @@
 apiVersion: v1
-kind: Service
+kind: PersistentVolume            # Create a PersistentVolume
 metadata:
-  name: polling-app-mysql
+  name: mysql-pv
   labels:
-    app: polling-app
+    type: local
 spec:
-  ports:
-    - port: 3306
-  selector:
-    app: polling-app
-    tier: mysql
-  clusterIP: None
----
+  storageClassName: standard      # The class of storage. A PV Claim requesting the same storageClass can be bound to this volume. 
+  capacity:
+    storage: 250Mi
+  accessModes:
+    - ReadWriteOnce
+  hostPath:                       # hostPath PersistentVolume is used for development and testing. It uses a file/directory on the Node to emulate network-attached storage
+    path: "/mnt/data"
+  persistentVolumeReclaimPolicy: Retain  # Retain the PersistentVolume even after PersistentVolumeClaim is deleted. The volume is considered “released”. But it is not yet available for another claim because the previous claimant’s data remains on the volume. 
+---    
 apiVersion: v1
-kind: PersistentVolumeClaim
-metadata:
+kind: PersistentVolumeClaim        # Create a PersistentVolumeClaim to request a PersistentVolume storage
+metadata:                          # Claim name and labels
   name: mysql-pv-claim
   labels:
     app: polling-app
-spec:
+spec:                              # Access mode and resource limits
+  storageClassName: standard       # Request a certain storage class
   accessModes:
-    - ReadWriteOnce
+    - ReadWriteOnce                # ReadWriteOnce means the volume can be mounted as read-write by a single Node
   resources:
     requests:
       storage: 250Mi
 ---
-apiVersion: apps/v1 # for versions before 1.9.0 use apps/v1beta2
-kind: Deployment
+apiVersion: v1                    # API version
+kind: Service                     # Type of kubernetes resource 
 metadata:
-  name: polling-app-mysql
-  labels:
+  name: polling-app-mysql         # Name of the resource
+  labels:                         # Labels that will be applied to the resource
+    app: polling-app
+spec:
+  ports:
+    - port: 3306
+  selector:                       # Selects any Pod with labels `app=polling-app,tier=mysql`
+    app: polling-app
+    tier: mysql
+  clusterIP: None
+---
+apiVersion: apps/v1
+kind: Deployment                    # Type of the kubernetes resource
+metadata:
+  name: polling-app-mysql           # Name of the deployment
+  labels:                           # Labels applied to this deployment 
     app: polling-app
 spec:
   selector:
-    matchLabels:
+    matchLabels:                    # This deployment applies to the Pods matching the specified labels
       app: polling-app
       tier: mysql
   strategy:
     type: Recreate
-  template:
+  template:                         # Template for the Pods in this deployment
     metadata:
-      labels:
+      labels:                       # Labels to be applied to the Pods in this deployment
         app: polling-app
         tier: mysql
-    spec:
+    spec:                           # The spec for the containers that will be run inside the Pods in this deployment
       containers:
-      - image: mysql:5.6
+      - image: mysql:5.6            # The container image
         name: mysql
-        env:
-        - name: MYSQL_ROOT_PASSWORD
-          valueFrom:
+        env:                        # Environment variables passed to the container 
+        - name: MYSQL_ROOT_PASSWORD 
+          valueFrom:                # Read environment variables from kubernetes secrets
             secretKeyRef:
               name: mysql-root-pass
               key: password
         - name: MYSQL_DATABASE
           valueFrom:
             secretKeyRef:
-              name: mysql-db
+              name: mysql-db-url
               key: database
         - name: MYSQL_USER
           valueFrom:
             secretKeyRef:
-              name: mysql-user
+              name: mysql-user-pass
               key: username
         - name: MYSQL_PASSWORD
           valueFrom:
             secretKeyRef:
-              name: mysql-pass
+              name: mysql-user-pass
               key: password
         ports:
-        - containerPort: 3306
+        - containerPort: 3306        # The port that the container exposes       
           name: mysql
         volumeMounts:
-        - name: mysql-persistent-storage
+        - name: mysql-persistent-storage  # This name should match the name specified in `volumes.name`
           mountPath: /var/lib/mysql
-      volumes:
+      volumes:                       # A PersistentVolume is mounted as a volume to the Pod  
       - name: mysql-persistent-storage
         persistentVolumeClaim:
-          claimName: mysql-pv-claim
+          claimName: mysql-pv-claim

deployments/polling-app-client.yaml

@@ -1,38 +1,38 @@
-apiVersion: apps/v1
-kind: Deployment
+apiVersion: apps/v1             # API version
+kind: Deployment                # Type of kubernetes resource
 metadata:
-  name: polling-app-client
+  name: polling-app-client      # Name of the kubernetes resource
 spec:
-  replicas: 1
-  selector:
-    matchLabels:
-      name: polling-app-client
-  template:
+  replicas: 1                   # No of replicas/pods to run
+  selector:                     
+    matchLabels:                # This deployment applies to Pods matching the specified labels
+      app: polling-app-client
+  template:                     # Template for creating the Pods in this deployment
     metadata:
-      labels:
-        name: polling-app-client
-    spec:
+      labels:                   # Labels that will be applied to all the Pods in this deployment
+        app: polling-app-client
+    spec:                       # Spec for the containers that will run inside the Pods
       containers:
       - name: polling-app-client
         image: callicoder/polling-app-client:1.0.0
         imagePullPolicy: IfNotPresent
         ports:
           - name: http
-            containerPort: 80
+            containerPort: 80   # Should match the Port that the container listens on
         resources:
           limits:
             cpu: 0.2
             memory: "10Mi"
 ---
-apiVersion: v1
-kind: Service
+apiVersion: v1                  # API version
+kind: Service                   # Type of kubernetes resource
 metadata:
-  name: polling-app-client
+  name: polling-app-client      # Name of the kubernetes resource
 spec:
-  type: NodePort
+  type: NodePort                # Exposes the service by opening a port on each node
   selector:
-    name: polling-app-client
-  ports:
+    app: polling-app-client     # Any Pod matching the label `app=polling-app-client` will be picked up by this service
+  ports:                        # Forward incoming connections on port 80 to the target port 80 in the Pod
   - name: http
     port: 80
     targetPort: 80

deployments/polling-app-server.yaml

@@ -1,59 +1,58 @@
----
-apiVersion: apps/v1
-kind: Deployment
+apiVersion: apps/v1           # API version
+kind: Deployment              # Type of kubernetes resource
 metadata:
-  name: polling-app-server
-  labels:
+  name: polling-app-server    # Name of the kubernetes resource
+  labels:                     # Labels that will be applied to this resource
     app: polling-app-server
 spec:
-  replicas: 1
+  replicas: 1                 # No. of replicas/pods to run in this deployment
   selector:
-    matchLabels:
+    matchLabels:              # The deployment applies to any pods mayching the specified labels
       app: polling-app-server
-  template:
+  template:                   # Template for creating the pods in this deployment
     metadata:
-      labels:
+      labels:                 # Labels that will be applied to each Pod in this deployment
         app: polling-app-server
-    spec:
+    spec:                     # Spec for the containers that will be run in the Pods
       containers:
       - name: polling-app-server
         image: callicoder/polling-app-server:1.0.0
         imagePullPolicy: IfNotPresent
         ports:
           - name: http
-            containerPort: 8080
+            containerPort: 8080 # The port that the container exposes
         resources:
           limits:
             cpu: 0.2
-            memory: "256Mi"
-        env:
-        - name: SPRING_DATASOURCE_USERNAME
-          valueFrom:
+            memory: "200Mi"
+        env:                  # Environment variables supplied to the Pod
+        - name: SPRING_DATASOURCE_USERNAME # Name of the environment variable
+          valueFrom:          # Get the value of environment variable from kubernetes secrets
             secretKeyRef:
-              name: mysql-user
+              name: mysql-user-pass
               key: username
         - name: SPRING_DATASOURCE_PASSWORD
           valueFrom:
             secretKeyRef:
-              name: mysql-pass
+              name: mysql-user-pass
               key: password
         - name: SPRING_DATASOURCE_URL
           valueFrom:
             secretKeyRef:
-              name: mysql-url
+              name: mysql-db-url
               key: url
 ---
-apiVersion: v1
-kind: Service
-metadata:
-  name: polling-app-server
-  labels:
+apiVersion: v1                # API version
+kind: Service                 # Type of the kubernetes resource
+metadata:                     
+  name: polling-app-server    # Name of the kubernetes resource
+  labels:                     # Labels that will be applied to this resource
     app: polling-app-server
-spec:
-  type: NodePort
+spec:                         
+  type: NodePort              # The service will be exposed by opening a Port on each node and proxying it. 
   selector:
-    app: polling-app-server
-  ports:
+    app: polling-app-server   # The service exposes Pods with label `app=polling-app-server`
+  ports:                      # Forward incoming connections on port 8080 to the target port 8080
   - name: http
     port: 8080
     targetPort: 8080