Kubernetes之动态Jenkins slave

一、前提

本次实践前，需已完成以下过程：

1、搭建好一个Kubernetes集群(本实践为单节点集群)，网上参考较多，不赘述。

2、选取kubernetes集群外的一台服务器安装 NFS服务端，并在集群内每个节点安装 NFS客户端;
NFS服务端所在的服务器IP为 10.141.211.178，记为 nfs server；而集群master服务器，记为 master;
(1) nfs server创建存储目录 /data/k8s/ 并执行命令：chmod 755 /data/k8s/, 并关闭防火墙
(2) nfs server安装NFS，执行: yum -y install nfs-utils rpcbind，
再配置NFS，执行：vi /etc/exports，在该文件内添加内容：/data/k8s *(rw,sync,no_root_squash)，
然后启动NFS服务，执行：

    # systemctl start rpcbind && systemctl enable rpcbind
    # systemctl start nfs && systemctl enable nfs

​ (3) master同样安装并启动NFS，执行：

    # yum -y install nfs-utils rpcbind
    # systemctl start rpcbind && systemctl enable rpcbind
    # systemctl start nfs && systemctl enable nfs

​ 再执行：showmount -e 10.141.211.178，可看到共享目录 /data/k8s

二、集群安装Jenkins

Jenkins master的安装，需要将数据持久化。可以利用NFS作为存储资源，创建PVC对象来挂载。PV/PVC配置文件pvc.yaml如下：

apiVersion: v1
kind: PersistentVolume
metadata:
  name: opspv
spec:
  capacity:
    storage: 20Gi
  accessModes:
  - ReadWriteMany
  persistentVolumeReclaimPolicy: Delete
  nfs:
    server: 10.141.211.178          #注意：此处为NFS服务器的地址
    path: /data/k8s

---
kind: PersistentVolumeClaim
apiVersion: v1
metadata:
  name: opspvc
  namespace: kube-ops
spec:
  accessModes:
    - ReadWriteMany
  resources:
    requests:
      storage: 20Gi

同时，对于即将创建的Jenkins master资源对象，需要授予其一些权限，比如增删改查等。相应的配置文件rbac.yaml如下：

apiVersion: v1
kind: ServiceAccount
metadata:
  name: jenkins
  namespace: kube-ops

---
kind: ClusterRole
apiVersion: rbac.authorization.k8s.io/v1beta1
metadata:
  name: jenkins
rules:
  - apiGroups: ["extensions", "apps"]
    resources: ["deployments"]
    verbs: ["create", "delete", "get", "list", "watch", "patch", "update"]
  - apiGroups: [""]
    resources: ["services"]
    verbs: ["create", "delete", "get", "list", "watch", "patch", "update"]
  - apiGroups: [""]
    resources: ["pods"]
    verbs: ["create","delete","get","list","patch","update","watch"]
  - apiGroups: [""]
    resources: ["pods/exec"]
    verbs: ["create","delete","get","list","patch","update","watch"]
  - apiGroups: [""]
    resources: ["pods/log"]
    verbs: ["get","list","watch"]
  - apiGroups: [""]
    resources: ["secrets"]
    verbs: ["get"]

---
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: ClusterRoleBinding
metadata:
  name: jenkins
  namespace: kube-ops
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: jenkins
subjects:
  - kind: ServiceAccount
    name: jenkins
    namespace: kube-ops

然后，基于jenkins/jenkins:lts 镜像创建jenkins master镜像，配置文件jenkins.yaml 如下：

apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  name: jenkins
  namespace: kube-ops
spec:
  template:
    metadata:
      labels:
        app: jenkins
    spec:
      terminationGracePeriodSeconds: 10
      serviceAccount: jenkins
      containers:
      - name: jenkins
        image: jenkins/jenkins:lts
        imagePullPolicy: IfNotPresent
        ports:
        - containerPort: 8080
          name: web
          protocol: TCP
        - containerPort: 50000
          name: agent
          protocol: TCP
        resources:
          limits:
            cpu: 1000m
            memory: 1Gi
          requests:
            cpu: 500m
            memory: 512Mi
        livenessProbe:
          httpGet:
            path: /login
            port: 8080
          initialDelaySeconds: 60
          timeoutSeconds: 5
          failureThreshold: 12
        readinessProbe:
          httpGet:
            path: /login
            port: 8080
          initialDelaySeconds: 60
          timeoutSeconds: 5
          failureThreshold: 12
        volumeMounts:
        - name: jenkinshome
          subPath: jenkins
          mountPath: /var/jenkins_home
        env:
        - name: LIMITS_MEMORY
          valueFrom:
            resourceFieldRef:
              resource: limits.memory
              divisor: 1Mi
        - name: JAVA_OPTS
          value: -Xmx$(LIMITS_MEMORY)m -XshowSettings:vm -Dhudson.slaves.NodeProvisioner.initialDelay=0 -Dhudson.slaves.NodeProvisioner.MARGIN=50 -Dhudson.slaves.NodeProvisioner.MARGIN0=0.85 -Duser.timezone=Asia/Shanghai
      securityContext:
        fsGroup: 1000
      volumes:
      - name: jenkinshome
        persistentVolumeClaim:
          claimName: opspvc

---
apiVersion: v1
kind: Service
metadata:
  name: jenkins
  namespace: kube-ops
  labels:
    app: jenkins
spec:
  selector:
    app: jenkins
  type: NodePort
  ports:
  - name: web
    port: 8080
    targetPort: web
    nodePort: 30002
  - name: agent
    port: 50000
    targetPort: agent

最后，在一个目录内分别创建以上3个文件，执行命令如下：

# kubectl create namespace kube-ops
# kubectl create -f pvc.yaml
# kubectl create -f rbac.yaml
# kubectl create -f jenkins.yaml(此步执行会出现文件权限问题，解决办法为：
          先在nfs server服务器执行：chown -R 1000 /data/k8s/jenkins
          然后在master执行：kubectl delete -f jenkins.yaml
          kubectl create -f jenkins.yaml  )

此时，我们通过命令kubectl -n kube-ops get pod可以查看到jenkins已成功创建。

三、Jenkins配置动态slave

1、初始化Jenkins配置

浏览器打开masterIP:30002，如下：

其中的管理员密码，我们既可以进入容器内对应的目录查看，也可以在nfs server服务器上执行命令：
cat /data/k8s/jenkins/secrets/initialAdminPassword 来查看；然后选择安装推荐的插件，如下：

然后添加管理员账户即可进入Jenkins界面。

2、配置jenkins slave

(1) 安装Kubernetes插件
进入 Manage Jenkins—>Manage Plugins—>可选插件(Available)—>Kubernetes plugin勾选，直接安装即可。
(2) 配置Kubernetes插件
点击Manage Jenkins—>Configure System—>云—>新增一个云—>Kubernetes，如下：

然后配置如下：
先注意 名称默认为kubernetes，然后 Kubernetes地址 填写https://kubernetes.default.svc.cluster.local，命名空间为kube-ops；接着点击右边的 连接测试 按钮，如果显示Connection test successful，表示Jenkins可以和Kubernetes集群正常通信了。最后，在Jenkins地址，填入：http://服务名.kube-ops.svc.cluster.local:8080，如下所示：

(3) 配置 Kubernetes Pod Template
关于 Kubernetes Pod Template部分的配置，其实就是对jenkins slave的配置。具体配置如下：

图中标记的地方较为重要，不要填错。其中标签列表部分 后面仍有用到；Docker 镜像部分，是本人基于 cnych/jenkins:jnlp6 镜像基础上继续定制的镜像，包含maven、docker、docker-compose、kubectl等工具。
另外，添加卷如下：

添加这两个 Host Path Volume，是为了更好地在jenkins slave容器中使用docker 和 kubectl 工具，所以挂载了宿主机的部分目录。
然后，设置Service Account如下：

最后，点击 保存 即可。

3.测试jenkins slave

首先新建一个 名为test 的 Freestyle project 项目，其配置如下：

这里的标签表达式，正是Kubernetes Pod Template的标签列表的内容。
然后，增加构建步骤—>执行shell，如下:

具体shell如下：

echo "测试 Kubernetes 动态生成 jenkins slave"

echo "===========mvn==========="
mvn --version
echo $PATH

echo "==============docker in docker==========="
which docker
docker version

echo "==============docker-compose==========="
docker-compose version

echo "=============kubectl============="
kubectl get pods

保存之后，点击 立即构建。控制台输出如下：

Started by user admin
Running as SYSTEM
Agent jnlp-slave-pk06f is provisioned from template Kubernetes Pod Template
---
apiVersion: "v1"
kind: "Pod"
metadata:
  annotations: {}
  labels:
    jenkins: "slave"
    jenkins/jnlp-slave: "true"
  name: "jnlp-slave-pk06f"
spec:
  containers:
  - env:
    - name: "JENKINS_SECRET"
      value: "********"
    - name: "JENKINS_AGENT_NAME"
      value: "jnlp-slave-pk06f"
    - name: "JENKINS_NAME"
      value: "jnlp-slave-pk06f"
    - name: "JENKINS_AGENT_WORKDIR"
      value: "/home/jenkins/agent"
    - name: "JENKINS_URL"
      value: "http://jenkins.kube-ops.svc.cluster.local:8080/"
    image: "zhongyuanzhao000/jenkins-slave:jnlp"
    imagePullPolicy: "IfNotPresent"
    name: "jnlp"
    resources:
      limits: {}
      requests: {}
    securityContext:
      privileged: false
    tty: true
    volumeMounts:
    - mountPath: "/var/run/docker.sock"
      name: "volume-0"
      readOnly: false
    - mountPath: "/root/.kube"
      name: "volume-1"
      readOnly: false
    - mountPath: "/home/jenkins/agent"
      name: "workspace-volume"
      readOnly: false
    workingDir: "/home/jenkins/agent"
  nodeSelector: {}
  restartPolicy: "Never"
  serviceAccount: "jenkins"
  volumes:
  - hostPath:
      path: "/var/run/docker.sock"
    name: "volume-0"
  - hostPath:
      path: "/root/.kube"
    name: "volume-1"
  - emptyDir:
      medium: ""
    name: "workspace-volume"

Building remotely on jnlp-slave-pk06f (jnlp-slave) in workspace /home/jenkins/agent/workspace/test
[test] $ /bin/sh -xe /tmp/jenkins3820575614440094591.sh
+ echo 测试 Kubernetes 动态生成 jenkins slave
测试 Kubernetes 动态生成 jenkins slave
+ echo ===========mvn===========
===========mvn===========
+ mvn --version
Apache Maven 3.6.1 (d66c9c0b3152b2e69ee9bac180bb8fcc8e6af555; 2019-04-05T03:00:29+08:00)
Maven home: /usr/local
Java version: 1.8.0_212, vendor: Oracle Corporation, runtime: /usr/local/openjdk-8/jre
Default locale: zh_CN, platform encoding: UTF-8
OS name: "linux", version: "3.10.0-327.el7.x86_64", arch: "amd64", family: "unix"
+ echo /usr/local/openjdk-8/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
/usr/local/openjdk-8/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
+ echo ==============docker in docker===========
==============docker in docker===========
+ which docker
/usr/local/bin/docker
+ docker version
Client: Docker Engine - Community
 Version:           18.09.8
 API version:       1.39
 Go version:        go1.10.8
 Git commit:        0dd43dd87f
 Built:             Wed Jul 17 17:38:58 2019
 OS/Arch:           linux/amd64
 Experimental:      false

Server: Docker Engine - Community
 Engine:
  Version:          18.09.7
  API version:      1.39 (minimum version 1.12)
  Go version:       go1.10.8
  Git commit:       2d0083d
  Built:            Thu Jun 27 17:26:28 2019
  OS/Arch:          linux/amd64
  Experimental:     false
+ echo ==============docker-compose===========
==============docker-compose===========
+ docker-compose version
docker-compose version 1.23.2, build 1110ad01
docker-py version: 3.6.0
CPython version: 3.6.7
OpenSSL version: OpenSSL 1.1.0f  25 May 2017
+ echo =============kubectl=============
=============kubectl=============
+ kubectl get pods
NAME                       READY   STATUS    RESTARTS   AGE
jenkins-575b84fb7b-59s5h   1/1     Running   0          29h
jnlp-slave-pk06f           1/1     Running   0          7s
Finished: SUCCESS

其中，你可以发现jenkins创建了jnlp-slave-pk06f的slave对象；而当该任务执行完之后，你在master上获取pod就会发现 jnlp-slave-pk06f 这个slave自动消失了，这就是动态jenkins slave的简单体现。

四、参考

本次实践得益于诸多运维大神对于知识的不吝分享，十分感谢！！！
具体参考的博客或指南如下：
基于 Jenkins 的 CI/CD (一) 强烈推荐阳明老师的博客
kubernetes实践：安装jenkins slave
kubernetes Jenkins gitlab搭建CI/CD环境 (二)
01 [从这里开始]Jenkins CI解决方案