Merge pull request #17 from marcel-dempers/persisted-volumes

persistent-volumes

kubernetes/persistentvolume/persistentvolume.yaml

@@ -0,0 +1,16 @@
+apiVersion: v1
+kind: PersistentVolume
+metadata:
+  name: example-volume
+  labels:
+    type: local
+spec:
+  #we use local node storage here!
+  #kubectl get storageclass
+  storageClassName: hostpath
+  capacity:
+    storage: 1Gi
+  accessModes:
+    - ReadWriteOnce
+  hostPath:
+    path: "/mnt/data"

kubernetes/persistentvolume/persistentvolumeclaim.yaml

@@ -0,0 +1,11 @@
+apiVersion: v1
+kind: PersistentVolumeClaim
+metadata:
+  name: example-claim
+spec:
+  storageClassName: hostpath
+  accessModes:
+    - ReadWriteOnce
+  resources:
+    requests:
+      storage: 50Mi

kubernetes/persistentvolume/postgres-no-pv.yaml

@@ -0,0 +1,50 @@
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: postgres-config
+  labels:
+    app: postgres
+data:
+  POSTGRES_DB: postgresdb
+  POSTGRES_USER: admin
+  POSTGRES_PASSWORD: admin123
+---
+apiVersion: apps/v1
+kind: StatefulSet
+metadata:
+  name: postgres
+spec:
+  serviceName: postgres
+  selector:
+    matchLabels:
+      app: postgres
+  replicas: 1
+  template:
+    metadata:
+      labels:
+        app: postgres
+    spec:
+      containers:
+        - name: postgres
+          image: postgres:10.4
+          imagePullPolicy: "IfNotPresent"
+          ports:
+            - containerPort: 5432
+          envFrom:
+            - configMapRef:
+                name: postgres-config
+---
+apiVersion: v1
+kind: Service
+metadata:
+  name: postgres
+  labels:
+    app: postgres
+spec:
+  selector:
+    app: postgres
+  ports:
+    - protocol: TCP
+      name: http
+      port: 5432
+      targetPort: 5432

kubernetes/persistentvolume/postgres-with-pv.yaml

@@ -0,0 +1,57 @@
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: postgres-config
+  labels:
+    app: postgres
+data:
+  POSTGRES_DB: postgresdb
+  POSTGRES_USER: admin
+  POSTGRES_PASSWORD: admin123
+---
+apiVersion: apps/v1
+kind: StatefulSet
+metadata:
+  name: postgres
+spec:
+  serviceName: postgres
+  selector:
+    matchLabels:
+      app: postgres
+  replicas: 1
+  template:
+    metadata:
+      labels:
+        app: postgres
+    spec:
+      containers:
+        - name: postgres
+          image: postgres:10.4
+          imagePullPolicy: "IfNotPresent"
+          ports:
+          - containerPort: 5432
+          envFrom:
+          - configMapRef:
+              name: postgres-config
+          volumeMounts:
+          - name: data
+            mountPath: /var/lib/postgresql/data
+      volumes:
+      - name: data
+        persistentVolumeClaim:
+          claimName: example-claim
+---
+apiVersion: v1
+kind: Service
+metadata:
+  name: postgres
+  labels:
+    app: postgres
+spec:
+  selector:
+    app: postgres
+  ports:
+    - protocol: TCP
+      name: http
+      port: 5432
+      targetPort: 5432

kubernetes/persistentvolume/readme.md

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+# Persisted Volumes Demo
+
+## Container Storage
+
+By default containers store their data on the file system like any other process.
+Container file system is temporary and not persisted during container restarts
+When container is recreated, so is the file system
+
+
+
+```
+# run postgres
+docker run -d --rm -e POSTGRES_DB=postgresdb -e POSTGRES_USER=admin -e POSTGRES_PASSWORD=admin123 postgres:10.4
+
+# enter the container 
+docker exec -it <container-id> bash
+
+# login to postgres
+psql --username=admin postgresdb
+
+#create a table
+CREATE TABLE COMPANY(
+   ID INT PRIMARY KEY     NOT NULL,
+   NAME           TEXT    NOT NULL,
+   AGE            INT     NOT NULL,
+   ADDRESS        CHAR(50),
+   SALARY         REAL
+);
+
+#show table
+\dt
+
+# quit 
+\q
+```
+
+Restarting the above container and going back in you will notice `\dt` commands returning no tables.
+Since data is lost.
+
+Same can be demonstrated using Kubernetes
+
+```
+cd .\kubernetes\persistedvolumes\
+
+kubectl create ns postgres
+kubectl apply -n postgres -f ./postgres-no-pv.yaml
+kubectl -n postgres get pods 
+kubectl -n postgres exec -it postgres-0 bash
+
+# run the same above mentioned commands to create and list the database table
+
+kubectl delete po -n postgres postgres-0
+
+# exec back in and confirm table does not exist.
+```
+
+# Persist data Docker
+
+```
+docker volume create postges
+docker run -d --rm -v postges:/var/lib/postgresql/data -e POSTGRES_DB=postgresdb -e POSTGRES_USER=admin -e POSTGRES_PASSWORD=admin123 postgres:10.4
+
+# run the same tests as above and notice
+```
+
+# Persist data Kubernetes
+
+
+```
+kubectl apply -f persistedvolume.yaml
+kubectl apply -n postgres -f persistedvolumeclaim.yaml
+
+kubectl apply -n postgres -f postgres-with-pv.yaml
+
+kubectl -n postgres get pods
+
+```