Knative 元件包含兩個大的領域，分別是Serving和Event。今天我們主要部署Serving部分。Serving，即服務，基於Kubernetes的crd提供縮容至零、請求驅動的計算功能。它本質上是無伺服器平臺的執行和擴充套件元件。主要有以下特性：
- 更高階層的抽象化，物件模型更易於理解
- 基於 HTTP 請求的無縫自動擴縮
- 逐步推出新版本
- 自動整合網路和服務網格
- 可插入：連線您自己的日誌記錄和監控平臺
Serving 元件
在本文中，我們將重點關注 Serving 子專案，因為它是深入瞭解 Knative 自然起點。 Knative Serving 使用者應該熟悉以下四個主要資源： Service（服務）、 Route（路由）、Configuration（配置）和 Revision（修訂）。
-
Service：
service.serving.knative.dev資源會自動管理您的工作負載的整個生命週期。它控制其他物件的建立，以確保您的應用為服務的每次更新都具有路由，配置和新修訂版。可以將服務定義為始終將流量路由到最新修訂版或固定修訂版。 -
Route：
route.serving.knative.dev資源將網路端點對映到一個或多個修訂版。您可以透過幾種方式管理流量，包括部分流量和命名路由。 -
Configuration：
configuration.serving.knative.dev資源維護部署的所需狀態。它在程式碼和配置之間提供了清晰的分隔，並遵循了十二要素應用程式方法。修改配置會建立一個新修訂。 -
Revision：
reversion.serving.knative.dev資源是對工作負載進行的每次修改的程式碼和配置的時間點快照。修訂是不可變的物件，可以保留很長時間。可以根據傳入流量自動縮放例項數。有關更多資訊，請參見配置自動縮放器。
部署
目前knative最新版本是v0.14，要求kubernetes版本v1.15+。以下命令將安裝Knative Serving元件。
安裝所需的CRD：
kubectl apply --filename https://github.com/knative/serving/releases/download/v0.14.0/serving-crds.yaml可以看到如下輸出：
customresourcedefinition.apiextensions.k8s.io/certificates.networking.internal.knative.dev created
customresourcedefinition.apiextensions.k8s.io/configurations.serving.knative.dev created
customresourcedefinition.apiextensions.k8s.io/ingresses.networking.internal.knative.dev created
customresourcedefinition.apiextensions.k8s.io/metrics.autoscaling.internal.knative.dev created
customresourcedefinition.apiextensions.k8s.io/podautoscalers.autoscaling.internal.knative.dev created
customresourcedefinition.apiextensions.k8s.io/revisions.serving.knative.dev created
customresourcedefinition.apiextensions.k8s.io/routes.serving.knative.dev created
customresourcedefinition.apiextensions.k8s.io/serverlessservices.networking.internal.knative.dev created
customresourcedefinition.apiextensions.k8s.io/services.serving.knative.dev created
customresourcedefinition.apiextensions.k8s.io/images.caching.internal.knative.dev created安裝Serving 核心元件
kubectl apply --filename https://github.com/knative/serving/releases/download/v0.14.0/serving-core.yaml可以看到如下輸出：
customresourcedefinition.apiextensions.k8s.io/images.caching.internal.knative.dev unchanged
namespace/knative-serving created
serviceaccount/controller created
clusterrole.rbac.authorization.k8s.io/knative-serving-admin created
clusterrolebinding.rbac.authorization.k8s.io/knative-serving-controller-admin created
image.caching.internal.knative.dev/queue-proxy created
configmap/config-autoscaler created
configmap/config-defaults created
configmap/config-deployment created
configmap/config-domain created
configmap/config-gc created
configmap/config-leader-election created
configmap/config-logging created
configmap/config-network created
configmap/config-observability created
configmap/config-tracing created
horizontalpodautoscaler.autoscaling/activator created
deployment.apps/activator created
service/activator-service created
deployment.apps/autoscaler created
service/autoscaler created
deployment.apps/controller created
service/controller created
deployment.apps/webhook created
service/webhook created
customresourcedefinition.apiextensions.k8s.io/certificates.networking.internal.knative.dev unchanged
customresourcedefinition.apiextensions.k8s.io/configurations.serving.knative.dev unchanged
customresourcedefinition.apiextensions.k8s.io/ingresses.networking.internal.knative.dev unchanged
customresourcedefinition.apiextensions.k8s.io/metrics.autoscaling.internal.knative.dev unchanged
customresourcedefinition.apiextensions.k8s.io/podautoscalers.autoscaling.internal.knative.dev unchanged
customresourcedefinition.apiextensions.k8s.io/revisions.serving.knative.dev unchanged
customresourcedefinition.apiextensions.k8s.io/routes.serving.knative.dev unchanged
customresourcedefinition.apiextensions.k8s.io/serverlessservices.networking.internal.knative.dev unchanged
customresourcedefinition.apiextensions.k8s.io/services.serving.knative.dev unchanged
clusterrole.rbac.authorization.k8s.io/knative-serving-addressable-resolver created
clusterrole.rbac.authorization.k8s.io/knative-serving-namespaced-admin created
clusterrole.rbac.authorization.k8s.io/knative-serving-namespaced-edit created
clusterrole.rbac.authorization.k8s.io/knative-serving-namespaced-view created
clusterrole.rbac.authorization.k8s.io/knative-serving-core created
clusterrole.rbac.authorization.k8s.io/knative-serving-podspecable-binding created
validatingwebhookconfiguration.admissionregistration.k8s.io/config.webhook.serving.knative.dev created
mutatingwebhookconfiguration.admissionregistration.k8s.io/webhook.serving.knative.dev created
validatingwebhookconfiguration.admissionregistration.k8s.io/validation.webhook.serving.knative.dev created
secret/webhook-certs created我們可以此時執行下面的命令，來檢視安裝了那些資源對下：
kubectl get all -n knative-serving可以看到：
NAME READY STATUS RESTARTS AGE
pod/activator-8cb6d456-fgm8b 1/1 Running 0 28s
pod/autoscaler-dd459ddbb-dk5bc 1/1 Running 0 28s
pod/controller-8564567c4c-jzlfg 1/1 Running 0 28s
pod/webhook-7fbf9c6d49-45lmq 1/1 Running 0 28s
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
service/activator-service ClusterIP 10.100.157.161 <none> 9090/TCP,8008/TCP,80/TCP,81/TCP 28s
service/autoscaler ClusterIP 10.100.73.90 <none> 9090/TCP,8008/TCP,8080/TCP,443/TCP 28s
service/controller ClusterIP 10.100.109.204 <none> 9090/TCP,8008/TCP 28s
service/webhook ClusterIP 10.100.101.64 <none> 9090/TCP,8008/TCP,443/TCP 28s
NAME READY UP-TO-DATE AVAILABLE AGE
deployment.apps/activator 1/1 1 1 28s
deployment.apps/autoscaler 1/1 1 1 28s
deployment.apps/controller 1/1 1 1 28s
deployment.apps/webhook 1/1 1 1 28s
NAME DESIRED CURRENT READY AGE
replicaset.apps/activator-8cb6d456 1 1 1 28s
replicaset.apps/autoscaler-dd459ddbb 1 1 1 28s
replicaset.apps/controller-8564567c4c 1 1 1 28s
replicaset.apps/webhook-7fbf9c6d49 1 1 1 28s
NAME REFERENCE TARGETS MINPODS MAXPODS REPLICAS AGE
horizontalpodautoscaler.autoscaling/activator Deployment/activator <unknown>/100% 1 20 1 28s選擇安裝網路層
此處Knative已經不再強依賴istio，除istio之外，我們可以選擇ambassador，contour，gloo，kourier。
此處因為Kourier相當於knative社群自己開發的網路層，有著更好的相容性，所以選擇Kourier。
安裝Knative Kourier controller控制器：
kubectl apply --filename https://github.com/knative/net-kourier/releases/download/v0.14.0/kourier.yaml有如下輸出：
namespace/kourier-system created
configmap/config-logging created
configmap/config-observability created
configmap/config-leader-election created
service/kourier created
deployment.apps/3scale-kourier-gateway created
deployment.apps/3scale-kourier-control created
clusterrole.rbac.authorization.k8s.io/3scale-kourier created
serviceaccount/3scale-kourier created
clusterrolebinding.rbac.authorization.k8s.io/3scale-kourier created
service/kourier-internal created
service/kourier-control created
configmap/kourier-bootstrap created執行以下命令檢視部署了那些資源：
kubectl get all -n kourier-system可以看到：
NAME READY STATUS RESTARTS AGE
pod/3scale-kourier-control-759cb78499-cph5g 1/1 Running 0 97s
pod/3scale-kourier-gateway-6f49d5768b-l7rsv 1/1 Running 0 97s
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
service/kourier LoadBalancer 10.100.81.199 ada062477a777476a8ed7fc989190fdf-1615177688.ap-southeast-1.elb.amazonaws.com 80:30588/TCP,443:30850/TCP 97s
service/kourier-control ClusterIP 10.100.163.167 <none> 18000/TCP 97s
service/kourier-internal ClusterIP 10.100.113.134 <none> 80/TCP 97s
NAME READY UP-TO-DATE AVAILABLE AGE
deployment.apps/3scale-kourier-control 1/1 1 1 97s
deployment.apps/3scale-kourier-gateway 1/1 1 1 97s
NAME DESIRED CURRENT READY AGE
replicaset.apps/3scale-kourier-control-759cb78499 1 1 1 97s
replicaset.apps/3scale-kourier-gateway-6f49d5768b 1 1 1 97s配置Serving 預設使用Kourier：
Serving的配置位於config-network configmap中，修改之前的內容為：
################################
# #
# EXAMPLE CONFIGURATION #
# #
################################
# This block is not actually functional configuration,
# but serves to illustrate the available configuration
# options and document them in a way that is accessible
# to users that `kubectl edit` this config map.
#
# These sample configuration options may be copied out of
# this example block and unindented to be in the data block
# to actually change the configuration.
# DEPRECATED:
# istio.sidecar.includeOutboundIPRanges is obsolete.
# The current versions have outbound network access enabled by default.
# If you need this option for some reason, please use global.proxy.includeIPRanges in Istio.
#
# istio.sidecar.includeOutboundIPRanges: "*"
# ingress.class specifies the default ingress class
# to use when not dictated by Route annotation.
#
# If not specified, will use the Istio ingress.
#
# Note that changing the Ingress class of an existing Route
# will result in undefined behavior. Therefore it is best to only
# update this value during the setup of Knative, to avoid getting
# undefined behavior.
ingress.class: "istio.ingress.networking.knative.dev"
# certificate.class specifies the default Certificate class
# to use when not dictated by Route annotation.
#
# If not specified, will use the Cert-Manager Certificate.
#
# Note that changing the Certificate class of an existing Route
# will result in undefined behavior. Therefore it is best to only
# update this value during the setup of Knative, to avoid getting
# undefined behavior.
certificate.class: "cert-manager.certificate.networking.knative.dev"
# domainTemplate specifies the golang text template string to use
# when constructing the Knative service's DNS name. The default
# value is "{{.Name}}.{{.Namespace}}.{{.Domain}}". And those three
# values (Name, Namespace, Domain) are the only variables defined.
#
# Changing this value might be necessary when the extra levels in
# the domain name generated is problematic for wildcard certificates
# that only support a single level of domain name added to the
# certificate's domain. In those cases you might consider using a value
# of "{{.Name}}-{{.Namespace}}.{{.Domain}}", or removing the Namespace
# entirely from the template. When choosing a new value be thoughtful
# of the potential for conflicts - for example, when users choose to use
# characters such as `-` in their service, or namespace, names.
# {{.Annotations}} can be used for any customization in the go template if needed.
# We strongly recommend keeping namespace part of the template to avoid domain name clashes
# Example '{{.Name}}-{{.Namespace}}.{{ index .Annotations "sub"}}.{{.Domain}}'
# and you have an annotation {"sub":"foo"}, then the generated template would be {Name}-{Namespace}.foo.{Domain}
domainTemplate: "{{.Name}}.{{.Namespace}}.{{.Domain}}"
# tagTemplate specifies the golang text template string to use
# when constructing the DNS name for "tags" within the traffic blocks
# of Routes and Configuration. This is used in conjunction with the
# domainTemplate above to determine the full URL for the tag.
tagTemplate: "{{.Tag}}-{{.Name}}"
# Controls whether TLS certificates are automatically provisioned and
# installed in the Knative ingress to terminate external TLS connection.
# 1. Enabled: enabling auto-TLS feature.
# 2. Disabled: disabling auto-TLS feature.
autoTLS: "Disabled"
# Controls the behavior of the HTTP endpoint for the Knative ingress.
# It requires autoTLS to be enabled.
# 1. Enabled: The Knative ingress will be able to serve HTTP connection.
# 2. Disabled: The Knative ingress will reject HTTP traffic.
# 3. Redirected: The Knative ingress will send a 302 redirect for all
# http connections, asking the clients to use HTTPS
httpProtocol: "Enabled"執行以下命令，完成修改工作：
kubectl patch configmap/config-network \
--namespace knative-serving \
--type merge \
--patch '{"data":{"ingress.class":"kourier.ingress.networking.knative.dev"}}'獲取外部IP或CNAME:
kubectl --namespace kourier-system get service kourier由於我們的叢集是eks，所以可以看到如下輸出：
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kourier LoadBalancer 10.100.47.159 a2f4c64ef34ea40b03d8933e1137ef-424fef949c9c7ad3.elb.ap-southeast-1.amazonaws.com 80:32327/TCP,443:31313/TCP 111s配置dns
此處可以使用Magic DNS（http://xip.io）, Real DNS以及Temporary DNS三種之一。
Magic DNS僅在叢集LoadBalancer服務公開了IPv4地址的情況下才有效，因此不適用於IPv6叢集，AWS或Minikube之類的本地設定。
生產環境的話，應該考慮使用Real DNS。
前面已經提到，我們使用的eks，決定了網路層（Service kourier的外部地址）返回的是一個CNAME。所以我們需要為domain配置CNAME記錄。此處我們將http://knative.example.com 替換為http://serverless.xx.me 。
# Here knative.example.com is the domain suffix for your cluster
*.serverless.xx.me == CNAME a2f4c64ef34ea40b03d8933e1137ef-424fef949c9c7ad3.elb.ap-southeast-1.amazonaws.com一旦你的dns提供商已經配置完成，你需要修改從configmap config-domain 告訴Knative去使用你自定義的domain：
修改之前我們看下預設的config-domain內容：
################################
# #
# EXAMPLE CONFIGURATION #
# #
################################
# This block is not actually functional configuration,
# but serves to illustrate the available configuration
# options and document them in a way that is accessible
# to users that `kubectl edit` this config map.
#
# These sample configuration options may be copied out of
# this example block and unindented to be in the data block
# to actually change the configuration.
# Default value for domain.
# Although it will match all routes, it is the least-specific rule so it
# will only be used if no other domain matches.
example.com: |
# These are example settings of domain.
# example.org will be used for routes having app=nonprofit.
example.org: |
selector:
app: nonprofit
# Routes having domain suffix of 'svc.cluster.local' will not be exposed
# through Ingress. You can define your own label selector to assign that
# domain suffix to your Route here, or you can set the label
# "serving.knative.dev/visibility=cluster-local"
# to achieve the same effect. This shows how to make routes having
# the label app=secret only exposed to the local cluster.
svc.cluster.local: |
selector:
app: secret那麼執行下面的命令完成修改，
# Replace knative.example.com with your domain suffix
kubectl patch configmap/config-domain \
--namespace knative-serving \
--type merge \
--patch '{"data":{"serverless.xx.me":""}}'檢視所有的Knative 元件執行狀態，如果STATUS是Running或者 Completed 即部署成功。
kubectl get pods --namespace knative-serving
NAME READY STATUS RESTARTS AGE
activator-8cb6d456-fgm8b 1/1 Running 0 3h19m
autoscaler-dd459ddbb-dk5bc 1/1 Running 0 3h19m
controller-8564567c4c-jzlfg 1/1 Running 0 3h19m
webhook-7fbf9c6d49-45lmq 1/1 Running 0 3h19m部署可選元件
可選元件主要包括：
- HPA autoscaling
- TLS with cert-manager
- TLS via HTTP01
- TLS wildcard support
可以根據實際需求選擇部署。
Hello World
接下來展示如何使用Knative部署應用程式，然後使用cURL請求與之互動。
示例程式
本指南演示了從Google Container Registry部署Hello World示例應用程式（Go）的基本工作流程。您可以使用這些步驟作為從其他登錄檔（例如Docker Hub）部署自己的容器映象的指南。
要部署本地容器映象，您需要透過執行以下命令來禁用映象標籤解析：
# Set to dev.local/local-image when deploying local container images
docker tag local-image dev.local/local-image部署應用
要使用Knative部署應用，您需要一個配置.yaml的檔案來定義服務。有關Service物件的更多資訊，請參見資源型別文件。
此配置檔案指定有關應用程式的後設資料，指向要部署的應用程式的託管映象，並允許配置部署。有關可用的配置選項的更多資訊，請參閱服務規範文件。
建立一個名為service.yaml的新檔案，然後將以下內容複製並貼上到其中：
apiVersion: serving.knative.dev/v1 # Current version of Knative
kind: Service
metadata:
name: helloworld-go # The name of the app
namespace: default # The namespace the app will use
spec:
template:
spec:
containers:
- image: gcr.io/knative-samples/helloworld-go # The URL to the image of the app
env:
- name: TARGET # The environment variable printed out by the sample app
value: "Go Sample v1"執行以下命令完成建立：
kubectl apply --filename service.yaml現在，您的服務已建立，Knative將執行以下步驟：
- 為此版本的應用程式建立一個新的不變版本。
- 執行網路程式設計以為您的應用建立路由，入口，服務和負載平衡器。
- 根據流量自動上下縮放Pod，包括將活動Pod調整為零。
詳情如下：
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
service/helloworld-go ExternalName <none> kourier-internal.kourier-system.svc.cluster.local <none> 3m9s
service/helloworld-go-vx6cf ClusterIP 10.100.14.241 <none> 80/TCP 3m40s
service/helloworld-go-vx6cf-private ClusterIP 10.100.100.96 <none> 80/TCP,9090/TCP,9091/TCP,8022/TCP 3m40s
service/kubernetes ClusterIP 10.100.0.1 <none> 443/TCP 10d
NAME READY UP-TO-DATE AVAILABLE AGE
deployment.apps/helloworld-go-vx6cf-deployment 0/0 0 0 3m40s
NAME DESIRED CURRENT READY AGE
replicaset.apps/helloworld-go-vx6cf-deployment-6fcdd7b9cd 0 0 0 3m40s
NAME LATESTCREATED LATESTREADY READY REASON
configuration.serving.knative.dev/helloworld-go helloworld-go-vx6cf helloworld-go-vx6cf True
NAME CONFIG NAME K8S SERVICE NAME GENERATION READY REASON
revision.serving.knative.dev/helloworld-go-vx6cf helloworld-go helloworld-go-vx6cf 1 True
NAME URL READY REASON
route.serving.knative.dev/helloworld-go http://helloworld-go.default.serverless.xx.me True
NAME URL LATESTCREATED LATESTREADY READY REASON
service.serving.knative.dev/helloworld-go http://helloworld-go.default.serverless.xx.me helloworld-go-vx6cf helloworld-go-vx6cf True發起請求，測試並觀察結果：
curl http://helloworld-go.default.serverless.xx.me
Hello World: Go Sample v1!至此，我們的使用knative 部署了hello-world應用，並且測試成功。
結論
本文簡單介紹了Knative serving以及部署以及hello-world demo。接下來我們會透過解讀hello-world，梳理一下整個Knative serving的實現。