• Kubernetes stateful set讲解以及一个基于postgreSQL的具体例子


    Stateful Set是Kubernetes 1.9版本新引入的一个概念,用于管理有状态的应用。

    Kubernetes官方文档:

    https://kubernetes.io/docs/concepts/workloads/controllers/statefulset/

    Manages the deployment and scaling of a set of Pods, and provides guarantees about the ordering and uniqueness of these Pods.

    Like a Deployment, a StatefulSet manages Pods that are based on an identical container spec. Unlike a Deployment, a StatefulSet maintains a sticky identity for each of their Pods. These pods are created from the same spec, but are not interchangeable: each has a persistent identifier that it maintains across any rescheduling.

    StatefulSet由以下几个部分组成:

    1. 用于定义网络标志(DNS domain)的Headless Service

    2. 用于创建PersistentVolumes的volumeClaimTemplates

    3. 定义具体应用的StatefulSet

    下面我给出了一个实际应用中的StatefulSet的yaml文件:

    ---
    
    apiVersion: apps/v1
    
    kind: StatefulSet
    
    metadata:
    
    name: ads-db-statefulset
    
    labels:
    
    component: ads
    
    module: db
    
    spec:
    
    serviceName: ads-db-service
    
    replicas: 1
    
    selector:
    
    matchLabels:
    
    component: ads
    
    module: db
    
    template:
    
    metadata:
    
    labels:
    
    component: ads
    
    module: db
    
    spec:
    
    volumes:
    
    - name: init
    
    secret:
    
    secretName: ads-db-secret
    
    items:
    
    - key: initdb.sql
    
    path: initdb.sql
    
    containers:
    
    - name: ads-db-pod
    
    image: postgres:9.6
    
    ports:
    
    - containerPort: 5432
    
    name: ads-db-port
    
    volumeMounts:
    
    - name: ads-db-volume
    
    mountPath: /var/lib/postgresql/data/
    
    - name: init
    
    mountPath: /docker-entrypoint-initdb.d/
    
    env:
    
    - name: PGDATA
    
    valueFrom:
    
    configMapKeyRef:
    
    name: ads-db-configmap
    
    key: pgdata_value
    
    - name: POSTGRES_PASSWORD
    
    valueFrom:
    
    secretKeyRef:
    
    name: ads-db-secret
    
    key: postgres_password_value
    
    volumeClaimTemplates:
    
    - metadata:
    
    name: ads-db-volume
    
    labels:
    
    component: ads
    
    module: db
    
    spec:
    
    accessModes: [ "ReadWriteOnce" ]
    
    resources:
    
    requests:
    
    storage: 1Gi
    

    使用kubectl get statefulset查看生成的statefulset:

    生成的headless service:

    生成的pod:

    当我把statefulset yaml文件里的replicas从1改成3之后,果然观察到有两个新的pod正在启动,并且名称满足命名规范-X。

    使用kubectl describe查看创建的statefulset明细:

    statefulSet自动创建的persistentVolumeClaim:

    The files belonging to this database system will be owned by user "postgres".

    This user must also own the server process.

    The database cluster will be initialized with locale "en_US.utf8".

    The default database encoding has accordingly been set to "UTF8".

    The default text search configuration will be set to "english".

    Data page checksums are disabled.

    fixing permissions on existing directory /var/lib/postgresql/data/pgdata ... ok

    creating subdirectories ... ok

    selecting default max_connections ... 100

    selecting default shared_buffers ... 128MB

    selecting dynamic shared memory implementation ... posix

    creating configuration files ... ok

    running bootstrap script ... ok

    performing post-bootstrap initialization ... ok

    syncing data to disk ... ok

    Success. You can now start the database server using:

    pg_ctl -D /var/lib/postgresql/data/pgdata -l logfile start

    使用下面的命令登录到statefulset提供的postgreSQL服务器上:

    1. kubectl run tester -it --rm --image=postgres:9.6 --env="PGCONNECT_TIMEOUT=5" --command -- bash

    看到root$之后,说明我们已经连接上pod了。

    使用如下命令行连接postgreSQL服务器:

    psql -h ads-db-statefulset-0.ads-db-service -p 5432 -U adsuser -W ads

    当然如果不用命令行,也可以使用pgadmin,以图形化界面连接statefulSet里的postgreSQL服务器:

    sudo apt install pgadmin3

    进行端口转发,这样我们可以使用localhost:5432进行连接:

    kubectl port-forward ads-db-statefulset-0 5432:5432

    也能成功连接:

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  • 原文地址:https://www.cnblogs.com/sap-jerry/p/9992527.html
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