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April 24, 2021 10:09 am GMT
Original Link: https://dev.to/vumdao/cdk8s-example-2glk
CDK8S Example
CDK8s is a software development framework for defining Kubernetes applications and reusable abstractions using familiar programming languages and rich object-oriented APIs. CDK8s generates pure Kubernetes YAML - you can use CDK8s to define applications for any Kubernetes cluster running anywhere.
This post provides you some examples of cdk8s python code to create k8s deployments, services, readiness and livness probes, statefulset, persitent volume and cronjob
Whats In This Document
- Getting Started With cdk8s
- Create cluster IP deployment and target port service
- Create deployment app with readiness and liveness probes
- Create statefulset with persisten volume
- Create secret attach to deployment
- Create cronjob with persistent volume claim
- Conclusion
Getting Started With cdk8s
- Prerequisites
- Python >= 3.7.7
- pipenv version 2018.11.26 or above.
- New Project
$ mkdir hello$ cd hello$ cdk8s init python-appInitializing a project from the python-app templateCreate cluster IP deployment and target port service
from constructs import Constructfrom imports import k8sclass ClusterIp(Construct): def __init__(self, scope: Construct, id: str): super().__init__(scope, id) app_name = 'wappip' label = {'app': app_name} k8s.KubeDeployment( self, "ClusterIpDeployment", metadata=k8s.ObjectMeta(name=app_name), spec=k8s.DeploymentSpec( replicas=2, selector=k8s.LabelSelector(match_labels=label), template=k8s.PodTemplateSpec( metadata=k8s.ObjectMeta(labels=label, name=app_name), spec=k8s.PodSpec( containers=[k8s.Container( name=app_name, image="katacoda/docker-http-server:latest", ports=[k8s.ContainerPort(container_port=80)] )] ) ) ) ) k8s.KubeService( self, 'ClusterIpService', metadata=k8s.ObjectMeta(name=app_name), spec=k8s.ServiceSpec( type='NodePort', ports=[k8s.ServicePort(port=80, node_port=30080, name="80")], selector=label ) ) k8s.KubeService( self, 'ClusterIpTargetPortService', metadata=k8s.ObjectMeta(name=f"{app_name}-targetport"), spec=k8s.ServiceSpec( ports=[k8s.ServicePort(port=8080, target_port=k8s.IntOrString.from_number(80), name="8080")], selector=label ) )#!/usr/bin/env pythonfrom constructs import Constructfrom cdk8s import App, Chartfrom clusterip import ClusterIpclass MyChart(Chart): def __init__(self, scope: Construct, id: str): super().__init__(scope, id) ClusterIp(self, 'clusterip')app = App()MyChart(app, "clusterip")app.synth()- Run
$ cdk8s synthdist/clusterip.k8s.yaml $ cat dist/clusterip.k8s.yaml apiVersion: apps/v1kind: Deploymentmetadata: name: wappipspec: replicas: 2 selector: matchLabels: app: wappip template: metadata: labels: app: wappip name: wappip spec: containers: - image: katacoda/docker-http-server:latest name: wappip ports: - containerPort: 80--------apiVersion: v1kind: Servicemetadata: name: wappipspec: ports: - name: "80" nodePort: 30080 port: 80 selector: app: wappip type: NodePort--------apiVersion: v1kind: Servicemetadata: name: wappip-targetportspec: ports: - name: "8080" port: 8080 targetPort: 80 selector: app: wappipCreate deployment app with readiness and liveness probes
from constructs import Constructfrom imports import k8simport reclass ReadinessLivenesProbes(Construct): def __init__(self, scope: Construct, id: str): super().__init__(scope, id) for _name in ['frontend', 'bad-frontend']: if re.search('bad', _name): image_tag = 'unhealthy' toleration = k8s.Toleration() affinity = k8s.Affinity() else: image_tag = 'health' toleration = k8s.Toleration( effect='NoSchedule', key='fe', operator='Equal', value='healthy' ) affinity = k8s.Affinity( node_affinity=k8s.NodeAffinity( required_during_scheduling_ignored_during_execution=k8s.NodeSelector( node_selector_terms=[ k8s.NodeSelectorTerm( match_expressions=[ k8s.NodeSelectorRequirement( key='kubernetes.io/hostname', operator='In', values=['kube1'] ) ] ) ] ) ) ) label = {'app': _name} k8s.KubeDeployment( self, f"FrontendHealthy{_name}", metadata=k8s.ObjectMeta(labels=label, name=_name), spec=k8s.DeploymentSpec( replicas=1, selector=k8s.LabelSelector(match_labels=label), template=k8s.PodTemplateSpec( metadata=k8s.ObjectMeta(labels=label), spec=k8s.PodSpec( containers=[ k8s.Container( name=_name, image=f"katacoda/docker-http-server:{image_tag}", ports=[k8s.ContainerPort(container_port=80)], resources=k8s.ResourceRequirements( limits={"memory": k8s.Quantity.from_string('3000Mi'), "cpu": k8s.Quantity.from_string('1000m')}, requests={"memory": k8s.Quantity.from_string('300Mi'), "cpu": k8s.Quantity.from_string('200m')} ), readiness_probe=k8s.Probe( http_get=k8s.HttpGetAction(port=k8s.IntOrString.from_number(80), path='/'), initial_delay_seconds=1, timeout_seconds=1 ), liveness_probe=k8s.Probe( http_get=k8s.HttpGetAction(port=k8s.IntOrString.from_number(80), path='/'), initial_delay_seconds=1, failure_threshold=3, timeout_seconds=1 ) ) ], tolerations=[toleration], affinity=affinity ) ) ) )Create statefulset with persisten volume
from constructs import Construct, Nodefrom imports import k8sclass StateFulSet(Construct): def __init__(self, scope: Construct, id: str): super().__init__(scope, id) msql_name = 'msql' msql_label = {'ss': msql_name} k8s.KubeStatefulSet( self, "MsqlStatefulSet", metadata=k8s.ObjectMeta(name=msql_name), spec=k8s.StatefulSetSpec( replicas=1, selector=k8s.LabelSelector(match_labels=msql_label), service_name=msql_name, template=k8s.PodTemplateSpec( metadata=k8s.ObjectMeta(labels=msql_label, name=msql_name), spec=k8s.PodSpec( containers=[k8s.Container( name=msql_name, image="openshift/mysql-55-centos7", ports=[k8s.ContainerPort(container_port=3306)], env=[ k8s.EnvVar(name='MYSQL_ROOT_PASSWORD', value='yourpassword'), k8s.EnvVar(name='MYSQL_USER', value='wp_user'), k8s.EnvVar(name='MYSQL_PASSWORD', value='wp_pass'), k8s.EnvVar(name='MYSQL_DATABASE', value='wp_db'), ], volume_mounts=[k8s.VolumeMount(mount_path='/var/lib/mysql/data', name='mysql-persistent-storage')] )] ) ), volume_claim_templates=[ k8s.KubePersistentVolumeClaimProps( metadata=k8s.ObjectMeta(name="mysql-persistent-storage"), spec=k8s.PersistentVolumeClaimSpec( access_modes=["ReadWriteOnce"], resources=k8s.ResourceRequirements(requests={"storage": k8s.Quantity.from_string("2Gi")}) ) ) ] ) ) k8s.KubePersistentVolume( self, "STSPersistentVolume1", metadata=k8s.ObjectMeta(name='nfs-0001'), spec=k8s.PersistentVolumeSpec( access_modes=['ReadWriteOnce', 'ReadWriteMany'], capacity={'storage': k8s.Quantity.from_string('2Gi')}, nfs=k8s.NfsVolumeSource(path='/exports/data-0001', server='192.168.121.210'), persistent_volume_reclaim_policy='Retain' ) ) k8s.KubePersistentVolume( self, "STSPersistentVolume2", metadata=k8s.ObjectMeta(name='nfs-0002'), spec=k8s.PersistentVolumeSpec( access_modes=['ReadWriteOnce', 'ReadWriteMany'], capacity={'storage': k8s.Quantity.from_string('5Gi')}, nfs=k8s.NfsVolumeSource(path='/exports/data-0002', server='192.168.121.210'), persistent_volume_reclaim_policy='Retain' ) )Create secret attach to deployment
from constructs import Construct, Nodefrom imports import k8sclass Secrete(Construct): def __init__(self, scope: Construct, id: str): super().__init__(scope, id) app_name = 'myscecret' label = {'app': app_name} k8s.KubeDeployment( self, "SecreteDeployment", metadata=k8s.ObjectMeta(name=app_name), spec=k8s.DeploymentSpec( replicas=1, selector=k8s.LabelSelector(match_labels=label), template=k8s.PodTemplateSpec( metadata=k8s.ObjectMeta(labels=label, name=app_name), spec=k8s.PodSpec( containers=[ k8s.Container( name=app_name, image="alpine:latest", ports=[k8s.ContainerPort(container_port=80)], command=['sleep', '9999'], env=[ k8s.EnvVar( name='SECRET_USERNAME', value_from=k8s.EnvVarSource( secret_key_ref=k8s.SecretKeySelector(key='username', name='test-secret') ) ), k8s.EnvVar( name='SECRET_PASSWORD', value_from=k8s.EnvVarSource( secret_key_ref=k8s.SecretKeySelector(key='password', name='test-secret') ) ) ] ) ] ) ) ) ) k8s.KubeSecret( self, 'Secrete', metadata=k8s.ObjectMeta(name='test-secret'), type='Opaque', data={"username": "YWRtaW4=", "password": "YTYyZmpiZDM3OTQyZGNz"} )Create cronjob with persistent volume claim
from constructs import Construct, Nodefrom imports import k8sclass DocCronjob(Construct): def __init__(self, scope: Construct, id: str): super().__init__(scope, id) app_name = 'doc-clean' label = {'app': app_name} k8s.KubeCronJobV1Beta1( self, "DocCronjob", metadata=k8s.ObjectMeta(name=app_name, labels=label), spec=k8s.CronJobSpec( job_template=k8s.JobTemplateSpec( metadata=k8s.ObjectMeta(name=app_name), spec=k8s.JobSpec( template=k8s.PodTemplateSpec( metadata=k8s.ObjectMeta(name=app_name), spec=k8s.PodSpec( containers=[ k8s.Container( name=app_name, image="busybox", volume_mounts=[k8s.VolumeMount(mount_path='/opt/Documents', name='efs')], args=['/bin/sh', '-c', 'find /opt/Documents/Viewer/cache -type d -mtime +6 -exec rm -r {} \;; find /opt/Documents/Viewer -type f -mtime +6 -exec rm {} \;' ] ), ], restart_policy='OnFailure', volumes=[ k8s.Volume( name='efs', persistent_volume_claim=k8s.PersistentVolumeClaimVolumeSource( claim_name='efs-pvc' ) ) ] ) ) ) ), schedule='0 1 * * SAT' ) )Conclusion
cdk8s is just being in beta version, you should consider to use it for production until it reaches a certain level of maturity (probably the first major version)
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Original Link: https://dev.to/vumdao/cdk8s-example-2glk
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