云原生之旅 – 11）基于 Kubernetes 动态伸缩 Jenkins Build Agents

前言

上一篇文章云原生之旅 – 10）手把手教你安装 Jenkins on Kubernetes我们介绍了在 Kubernetes 上安装 Jenkins，本文介绍下如何设置k8s pod作为Jenkins 构建job的 agent。

Jenkins master 和 agent 均以 pod 的形式运行在Kubernetes 节点上。Master 运行在其中一个节点上，其配置数据 Jenkins home 使用存储卷挂载，master pod重启不会导致数据丢失。agent 运行在各个节点上，根据需求动态创建并自动释放。这样做的好处很多，比如高可用，高伸缩性，资源利用率高。

关键词：Jenkins on Kubernetes 实践，Jenkins 和 Kubernetes，在Kubernetes上安装Jenkins，Jenkins 高可用安装，Jenkins 动态伸缩构建， Kubernetes Pod as Jenkins build agent

准备

1. 已搭建 Jenkins master on kubernetes云原生之旅 – 10）手把手教你安装 Jenkins on Kubernetes
2. 准备一个 Service Account，对目标 cluster 具有k8s admin权限，以便部署。
3. 防火墙已开通 Jenkins 出站到Docker hub，方便 push/pull image
4. 防火墙已开通 Jenkins 到 目标 cluster，以便部署。

插件安装

• Kubernetes Plugin
• Google Kubernetes Engine Plugin (我的例子是部署到 GKE cluster)

Jenkins 配置Manage Nodes and Clouds1. Go to `Manage Jenkins` –> `Manage Nodes and Clouds`2.Click `Configure Clouds`3.Add a new Cloud select `Kubernetes`4. Click `Kubernetes Cloud Detail5. Enter `jenkins` namespace in `Kubernetes Namespace` field6. Click `Test Connection` –> result show `Connected to Kubernetes v1.22.12-gke.2300`7. Click `Save`8. Enter `http://jenkins-service.jenkins.svc.cluster.local:8080` in `Jenkins URL` field9. Enter `jenkins-agent:50000` in `Jenkins tunnel` field

10. Click `Add Pod Template` then `Pod Template Details`

11. Input `Name`=`jenkins-agent`, `Namespace`=`jenkins`, `Labels`=`kubeagent`12. (Optional) 如果不添加 container template, the Jenkins Kubernetes plugin will use the default JNLP image from the Docker hub to spin up the agents.如果你要覆盖默认的jnlp image 可以 Click `Add Container` to add Container Template,输入 `Name`=`jnlp`, `Docker Image`=`your_registry/jenkins/inbound-agent:4.11-1-jdk11`

Ensure that you remove the sleep and 9999999 default argument from the container template.

Manage Credentials

• Add `Usernames with password` for docker hub account/pwd，比如 wade_test_dockerhub
• Add `Google Service Account from private key` 比如gcp_sa_json_key

Credentials 会在Jenkinsfile里面用到。

### 本文首发于博客园https://www.cnblogs.com/wade-xu/p/16863955.html

Test a freestyle projectGo to Jenkins home –> New Item and create a freestyle project，命名为 quick-test在 job description 部分, add the label `kubeagent` for `Restrict where this project can be run`.

这个label 和我们上面创建 pod template时用的label一致. 这样的话 Jenkins就知道用哪个pod template 作为agent container.

随便添加一个shell 作为build steps

点Build Now

查看Console Output

Agent jenkins-agent-l7hw9 is provisioned from template jenkins-agent......Building remotely on jenkins-agent-l7hw9 (kubeagent) in workspace /home/jenkins/agent/workspace/quick-test[quick-test] $ /bin/sh -xe /tmp/jenkins17573873264046707236.sh+ echo test pipelinetest pipelineFinished: SUCCESS

### 本文首发于博客园https://www.cnblogs.com/wade-xu/p/16863955.html

JenkinsfileCI接着我们用Jenkinsfile 写一个Declarative pipeline -build/push docker image 到docker hub首先需要定义一个 pod.yaml 作为启动 agent 的container

kind: Podspec:  containers:  # list of containers that you want present for your build, you can define a default container in the Jenkinsfile    - name: maven      image: maven:3.5.4-jdk-8-slim      command: ["tail", "-f", "/dev/null"]  # this or any command that is bascially a noop is required, this is so that you don't overwrite the entrypoint of the base container      imagePullPolicy: Always # use cache or pull image for agent      resources:  # request and limit the resources your build contaienr        requests:          memory: 4Gi          cpu: 2        limits:          memory: 4Gi          cpu: 2      volumeMounts:        - mountPath: /root/.m2 # maven .m2 cache directory          name: maven-home    - name: git      image: bitnami/git:2.38.1      imagePullPolicy: IfNotPresent      command: ["tail", "-f", "/dev/null"]      resources: # limit the resources your build contaienr        limits:          cpu: 100m          memory: 256Mi    - name: kubectl-kustomize      image: line/kubectl-kustomize:1.25.3-4.5.7      imagePullPolicy: IfNotPresent      command: ["tail", "-f", "/dev/null"]      resources: # limit the resources your build contaienr        limits:          cpu: 100m          memory: 256Mi    - name: docker      image: docker:18.06.1      command: ["tail", "-f", "/dev/null"]      imagePullPolicy: Always      volumeMounts:        - name: docker          mountPath: /var/run/docker.sock # We use the k8s host docker engine  volumes:    - name: docker      hostPath:        path: /var/run/docker.sock    - name: maven-home      persistentVolumeClaim:        claimName: maven-repo-storage

build-pod.yaml

在Jenkinsfile里面定义agent 使用这个yaml file

  agent {    kubernetes {      idleMinutes 3  // how long the pod will live after no jobs have run on it      yamlFile './build-pod.yaml'  // path to the pod definition relative to the root of our project       defaultContainer 'docker'  // define a default container if more than a few stages use it, otherwise default to jnlp container    }

下面步骤是 docker login/build/tag/push

environment { DOCKER_HUB_REGISTRY=’https://index.docker.io/v1/’ DOCKER_HUB_CREDS = credentials(‘wade_test_dockerhub’) }

stage('Build and Push Docker Image') {      steps {        script {          dir(dir_path) {            container('docker') {                // docker login, Using single-quotes instead of double-quotes when referencing these sensitive environment variables prevents this type of leaking.                sh 'echo $DOCKER_HUB_CREDS_PSW | docker login -u $DOCKER_HUB_CREDS_USR --password-stdin $DOCKER_HUB_REGISTRY'                // build image with git tag                sh """                docker build -t $PROJECT_IMAGE_WITH_TAG .                docker tag $PROJECT_IMAGE_WITH_TAG $DOCKER_HUB_CREDS_USR/$PROJECT_IMAGE_WITH_TAG                """                // push image_tag to docker hub                sh """                docker push $DOCKER_HUB_CREDS_USR/$PROJECT_IMAGE_WITH_TAG                """            }          }        }      }    }

我这里没有选择用docker.withRegistry

docker.withRegistry("$DOCKER_HUB_REGISTRY", "$DOCKER_HUB_CREDENTIAL") {}

因为会有不安全的log提示

WARNING! Using --password via the CLI is insecure. Use --password-stdin.

CI + Kustomize + CD

这个例子是上面的 CI 之后 加上 – 利用 Kustomize build K8S resource manifests 然后 CD 到一个 Cluster

Kustomize 可以参考云原生之旅 – 6）不能错过的一款 Kubernetes 应用编排管理神器 Kustomize

    // assume your k8s manifests in another repo, mine is same repo, just in order to show git clone step    stage('Checkout K8S manifests') {      steps {        script {          dir(dir_path) {            container('git') {              if (! fileExists('learning_by_doing/README.md')) {                sh """                git clone https://github.com/wadexu007/learning_by_doing.git                ls -lhrt                """              } else {                  sh 'echo manifes repo already exist.'              }            }          }        }      }    }    stage('Build manifests with Kustomize') {      steps {        script {          dir(dir_path) {            container('kubectl-kustomize') {                sh """                cd learning_by_doing/Kustomize/demo-manifests/services/demo-app/dev/                kustomize edit set image $DOCKER_HUB_CREDS_USR/$PROJECT_IMAGE_WITH_TAG                kustomize build > $WORKSPACE/$dir_path/deployment.yaml                """            }          }        }      }    }    stage('Deploy to GKE test cluster') {environment{PROJECT_ID = 'xperiences-eng-cn-dev'        CLUSTER_NAME = 'xpe-spark-test-gke'        REGION = 'asia-east2'        CREDENTIALS_ID = 'gcp_sa_json_key'      }      steps {        script {          dir(dir_path) {            container('kubectl-kustomize') {                sh """                chown 1000:1000 deployment.yaml                echo start to deploy to cluster $CLUSTER_NAME                """                step([                  $class: 'KubernetesEngineBuilder',                  projectId: env.PROJECT_ID,                  clusterName: env.CLUSTER_NAME,                  location: env.REGION,                  manifestPattern: 'deployment.yaml',                  credentialsId: env.CREDENTIALS_ID,                  verifyDeployments: false])                  // verifyDeployments does not work for non-default namespace            }          }        }      }    }

View CodePipeline: Input Step这个例子是利用 Jenkins pipeline的 Input step 来做一个人工介入Approve的步骤。 然后再来一个多cluster 部署，选不同region 部署到不同的cluster的示例。

    stage('Wait for SRE Approval') {      steps {        timeout(time:72, unit:'HOURS') {          input message: "Approved Prod deployment?", submitter: 'sre-team'        }      }    }    // deployment to multipe k8s clusters    stage('Deploy to GKE Prod cluster') {environment{PROJECT_ID = 'sre-cn-dev'        CREDENTIALS_ID = 'gcp_sa_json_key'        CLUSTER_COMMON_NAME = 'demo-gke-prod'      }      steps {        script {          env.REGION = input message: 'Choose which region you want to deploy?',                             parameters: [choice(name: 'Region',                                                description: 'Select Region to Deloy',                                                choices: ['europe-west1', 'us-central1'])                                          ]          dir(dir_path) {            if ( env.REGION == "europe-west1" ) {              def eu_cluster_name = env.CLUSTER_COMMON_NAME + "-eu"              container('kubectl-kustomize') {                  sh "echo deploy to cluster $eu_cluster_name in region: $REGION"              }            }            if ( env.REGION == "us-central1" ) {              def us_cluster_name = env.CLUSTER_COMMON_NAME + "-us"              container('kubectl-kustomize') {                  sh "echo deploy to cluster $us_cluster_name in region: $REGION"              }            }          }        }      }    }

所有例子均在我的 github repo。

### 本文首发于博客园https://www.cnblogs.com/wade-xu/p/16863955.html

测试现在你可以创建一个 Pipeline 或者 Multibranch Pipeline job 来测试。Repository URL = `https://github.com/wadexu007/learning_by_doing`Script Path, e.g. `Jenkins/k8s_pod_as_build_agent/demo-app-java/Jenkinsfile`你会看到每启动一个job 都会相应的产生一个pod 来作为Jenkins agent运行，结束后根据idleMinutes自动释放。总结如果你已经成功创建并测试 CI/CD pipeline，可以继续加强，比如加上 Post notifications最佳实践

• 设置resource requests and limits on each container in your Pod
• 如果使用maven 构建 java项目，.m2 cache目录需要 mount 出来，这样加快后面的maven build速度。
• 使用Jenkins Shared Libraries抽取Pipeline的共用代码
• 在容器里构建容器化应用（Run docker in docker) 我的例子是通过 mountdocker.sock 利用k8s 主机 docker engine来实现的，这种方式需要privileges mode 不安全，推荐使用Kaniko，下一篇文章会介绍。

感谢阅读，如果您觉得本文的内容对您的学习有所帮助，您可以打赏和推荐，您的鼓励是我创作的动力。 Learning by Doing