基于openkruise实现容器应用固定id
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背景说明
我们在业务上容器的过程中遇到了如下问题:
- 以deployment部署的应用pod,由于id经常变更,服务重启,监控变得难以维护。这里只是以监控为切入点,事实上,还有诸多应用需要与id强绑定。
- statefulset可以解决上面的问题,但是引入一个新的问题就是statefulset本身为了维护有状态的应用,所有的应用Pod启动是有严格的先后顺序,也就是串行启动,对于大规模的应用pod来讲,启动消耗时间太长,这是无法忍受的。
为解决以上问题,我们在容器平台当中引入了openkruise。
openkruise简介
项目地址: https://github.com/openkruise/kruise
详细的说明可以参考这篇文章: 《OpenKruise - 云原生应用自动化引擎正式开源》
从当前github上的文档来看,目前OpenKruise支持五种改进的控制器:
-
CloneSet: CloneSet is a workload that mainly focuses on managing stateless applications. It provides full features for more efficient, deterministic and controlled deployment, such as inplace update, specified pod deletion, configurable priority/scatter update, preUpdate/postUpdate hooks.
-
Advanced StatefulSet: An enhanced version of default StatefulSet with extra functionalities such as inplace-update, pause and MaxUnavailable.
-
SidecarSet: A controller that injects sidecar containers into the Pod spec based on selectors and also is able to upgrade the sidecar containers.
-
UnitedDeployment: This controller manages application pods spread in multiple fault domains by using multiple workloads.
-
BroadcastJob: A job that runs Pods to completion across all the nodes in the cluster.
UnitedDeployment是在StatefulSet基础上的更高级抽象,通过一个资源描述可以管理多个StatefulSet的实例组,可实现多实例组的灰度发布与滚动升级。
Broadcast Job实际上就是以DaemonSet的方式在所有节点上运行一次性Job
SidercarSet用于Sidercar注入及管理
而我们要使用到的正是其Advanced StatefulSet的特性。关于Advanced StatefulSet更详细的描述如下:
- 在kubernetes官方的statefulSet上做了功能扩展,更新策略由原来的只支持recreate,扩展为同时支持recreate和rollingupdate。rollingupdate还支持两种策略,一种是InPlaceIfPossible,另一种是InPlaceOnly。InPlaceIfPossible会尽可能的保证应用在原地升级(只支持镜像的升级,如果修改了yaml中的其他配置项,则无法保证);InPlaceOnly会保证应用一定在原地升级,但是它也只支持镜像的升级,如果修改了yaml中的其他配置项,会直接抛出异常。另外,原生的StatefulSet只能做到串行启动,Advanced StatefulSet可以做到并行启动。
部署openkruise
官方的安装文档可以直接参考这里:
https://github.com/openkruise/kruise/tree/master/docs/tutorial
我简单写下安装步骤:
wget https://github.com/openkruise/kruise/releases/download/v0.4.0/kruise-chart.tgz
tar xf kruise-chart.tgz
cd kruise
helm install openkruise ./ -n kube-system
目前openkruise已经更新到了v0.5.0的版本。也可以直接通过阿里云的应用目录来完成其安装。
下面说一下更详细的安装过程:
- 获取helm包
helm repo add incubator http://aliacs-k8s-cn-beijing.oss-cn-beijing.aliyuncs.com/app/charts-incubator/
helm search repo ack-kruise
helm fetch incubator/ack-kruise
tar xf ack-kruise-0.5.0.tgz
cd ack-kruise
修改values.yml文件如下:
# Default values for kruise.
revisionHistoryLimit: 3
manager:
# settings for log print
log:
# log level for kruise-manager
level: "4"
# image settings
image:
# repository for kruise-manager image
repository: hub.example.com/library/kruise-manager
# tag for kruise-manager image
tag: v0.5.0
# resources of kruise-manager container
resources:
limits:
cpu: 500m
memory: 1Gi
requests:
cpu: 500m
memory: 1Gi
metrics:
addr: localhost
port: 8080
custom_resource_enable: StatefulSet
其实这里就改了两个东西:
- image:默认是docker hub上的地址,我这里改到了私有镜像仓库
- custom_resource_enable:用于指定启用哪几种资源,如果不指定的话,openkruise支持的五种资源会全部启用,我这里只用到了StatefulSet,所以这里只启用了这一种资源
然后执行安装操作:
helm install ack-kruise -n kube-system ./
安装完后,会生成以下五种crd:
# kubectl get crds |grep kruise
broadcastjobs.apps.kruise.io 2020-04-26T10:29:28Z
clonesets.apps.kruise.io 2020-04-26T10:29:28Z
sidecarsets.apps.kruise.io 2020-04-26T10:29:28Z
statefulsets.apps.kruise.io 2020-04-26T10:29:28Z
uniteddeployments.apps.kruise.io 2020-04-26T10:29:28Z
同时会创建一个kruise-system的命名空间,并在里面生成一个pod:
# kubectl get pods -n kruise-system
NAME READY STATUS RESTARTS AGE
kruise-controller-manager-0 1/1 Running 0 55m
验证statefulset资源的webhook是否被正常创建:
# kubectl get mutatingwebhookconfiguration -o yaml
apiVersion: v1
items:
- apiVersion: admissionregistration.k8s.io/v1
kind: MutatingWebhookConfiguration
metadata:
creationTimestamp: "2020-04-26T10:29:28Z"
generation: 3
name: kruise-mutating-webhook-configuration
resourceVersion: "622944921"
selfLink: /apis/admissionregistration.k8s.io/v1/mutatingwebhookconfigurations/kruise-mutating-webhook-configuration
uid: 303a7b7f-3a62-49d7-8ef6-082ea288eeb2
webhooks:
- admissionReviewVersions:
- v1beta1
clientConfig:
caBundle: xxxxx
service:
name: kruise-webhook-server-service
namespace: kruise-system
path: /mutating-create-update-statefulset
port: 443
failurePolicy: Fail
matchPolicy: Exact
name: mutating-create-update-statefulset.kruise.io
namespaceSelector:
matchExpressions:
- key: control-plane
operator: DoesNotExist
objectSelector: {}
reinvocationPolicy: Never
rules:
- apiGroups:
- apps.kruise.io
apiVersions:
- v1alpha1
operations:
- CREATE
- UPDATE
resources:
- statefulsets
scope: ‘*‘
sideEffects: Unknown
timeoutSeconds: 30
......
也是确保其他未用到的相关mutatingwebhook是关闭的。。在实际测试中,SidecarSet资源的mutatingwebhook可能会导致创建的pod出不来。
这些webhook本质上都是kubernetes的admissioncontrol,只要你安装了,哪怕没有使用,当你在执行相关操作时,都需要被所有的adminssioncontrol检测,如果admissioncontrol本身出了问题,就会导致请求无法响应的状态。同时这些webhook类型的adminssioncontrol也会拖慢响应速度。
用法示例
下面是官方提供的一个基于openkruise提供的statefulset资源的部署文件示例:
apiVersion: apps.kruise.io/v1alpha1
kind: StatefulSet
metadata:
name: demo-v1-guestbook-kruise
labels:
app.kubernetes.io/name: guestbook-kruise
app.kubernetes.io/instance: demo-v1
spec:
replicas: 3
serviceName: demo-v1-guestbook-kruise
selector:
matchLabels:
app.kubernetes.io/name: guestbook-kruise
app.kubernetes.io/instance: demo-v1
template:
metadata:
labels:
app.kubernetes.io/name: guestbook-kruise
app.kubernetes.io/instance: demo-v1
spec:
readinessGates:
# A new condition that ensures the pod remains at NotReady state while the in-place update is happening
- conditionType: InPlaceUpdateReady
containers:
- name: guestbook-kruise
image: openkruise/guestbook:v1
imagePullPolicy: Always
ports:
- name: http-server
containerPort: 3000
podManagementPolicy: Parallel # allow parallel updates, works together with maxUnavailable
updateStrategy:
type: RollingUpdate
rollingUpdate:
# Do in-place update if possible, currently only image update is supported for in-place update
podUpdatePolicy: InPlaceIfPossible
# Allow parallel updates with max number of unavailable instances equals to 2
maxUnavailable: 3
执行部署之后,启动pod示例如下:
# kubectl get pods |grep demo-v1
demo-v1-guestbook-kruise-0 1/1 Running 0 62s
demo-v1-guestbook-kruise-1 1/1 Running 0 62s
demo-v1-guestbook-kruise-2 1/1 Running 0 62s
也可通过如下操作查看资源状态:
# kubectl get sts.apps.kruise.io
NAME DESIRED CURRENT UPDATED READY AGE
demo-v1-guestbook-kruise 3 3 3 3 56s
openkruise提供的statefulset的资源名为
sts.apps.kruise.io
更详细的用法可参考:
-
Advanced StatefulSet具体的使用方法:https://github.com/openkruise/kruise/blob/master/docs/concepts/astatefulset/README.md
-
Advanced StatefulSet示例文件: https://github.com/openkruise/kruise/blob/master/docs/tutorial/v1/guestbook-statefulset.yaml
-
UnitedDeployment具体的使用方法: https://github.com/openkruise/kruise/blob/master/docs/tutorial/uniteddeployment.md
-
UnitedDeployment示例文件: https://raw.githubusercontent.com/kruiseio/kruise/master/docs/tutorial/v1/uniteddeployment.yaml
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