Linkerd 是 Kubernetes 的服务网格。它通过为您提供运行时调试(runtime debugging)、可观察性(observability)、可靠性(reliability)和安全性(security)，使运行服务更轻松、更安全 — 所有这些都不需要对您的代码进行任何更改。
服务网格是用于处理服务间通信的专用基础设施层。它负责通过包含现代云原生应用程序的复杂服务拓扑来可靠地传递请求。实际上，服务网格通常通过一组轻量级网络代理来实现，这些代理与应用程序代码一起部署，而不需要感知应用程序本身。— Willian Morgan Buoyant CEO
为什么我们需要 Service Mesh?
1.What's a service mesh? And why do I need one? 一文中做了详细的解释，这里不再赘述。拥抱云原生，微服务已进入 Service Mesh 时代。
https://buoyant.io/2020/10/12/what-is-a-service-mesh/
为什么折腾 Linkerd2 而不是 Istio?
2.Benchmarking Linkerd and Istio
https://linkerd.io/2021/05/27/linkerd-vs-istio-benchmarks/
部署环境
- 腾讯云 TKE K8S 集群(或你自建的私有 K8S 集群)
- CentOS 7.x
可先快速过一个官方上手教程，本文是基于此在腾讯云的实战详解。
- 快速上手 Linkerd v2 Service Mesh(服务网格)
- Getting Started
https://linkerd.io/2.10/getting-started
查看集群版本
kubectl version --short
Client Version: v1.16.9
Server Version: v1.16.9
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Linkerd2 CLI 安装
首先我们需要下载并安装最新版本的 linkerd CLI。
我们直接进入 Linkerd2 版本发行页面，查看最新版：
https://github.com/linkerd/linkerd2/releases/
这里我们下载 linkerd2-cli-edge-21.6.1-linux-amd64。
https://github.com/linkerd/linkerd2/releases/download/edge-21.6.1/linkerd2-cli-edge-21.6.1-linux-amd64
安装：
wget -c https://github.com/linkerd/linkerd2/releases/download/edge-21.6.1/linkerd2-cli-edge-21.6.1-linux-amd64
mv linkerd2-cli-edge-21.6.1-linux-amd64 /usr/local/bin/linkerd
chmod 755 /usr/local/bin/linkerd
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现在我们运行 linkerd，会看到如下信息：
Usage:
linkerd [command]
Available Commands:
check Check the Linkerd installation for potential problems
completion Output shell completion code for the specified shell (bash, zsh or fish)
diagnostics Commands used to diagnose Linkerd components
help Help about any command
identity Display the certificate(s) of one or more selected pod(s)
inject Add the Linkerd proxy to a Kubernetes config
install Output Kubernetes configs to install Linkerd
install-cni Output Kubernetes configs to install Linkerd CNI
jaeger jaeger manages the jaeger extension of Linkerd service mesh
multicluster Manages the multicluster setup for Linkerd
profile Output service profile config for Kubernetes
repair Output the secret/linkerd-config-overrides resource if it has been deleted
uninject Remove the Linkerd proxy from a Kubernetes config
uninstall Output Kubernetes resources to uninstall Linkerd control plane
upgrade Output Kubernetes configs to upgrade an existing Linkerd control plane
version Print the client and server version information
viz viz manages the linkerd-viz extension of Linkerd service mesh
Flags:
--api-addr string Override kubeconfig and communicate directly with the control plane at host:port (mostly for testing)
--as string Username to impersonate for Kubernetes operations
--as-group stringArray Group to impersonate for Kubernetes operations
--cni-namespace string Namespace in which the Linkerd CNI plugin is installed (default "linkerd-cni")
--context string Name of the kubeconfig context to use
-h, --help help for linkerd
--kubeconfig string Path to the kubeconfig file to use for CLI requests
-L, --linkerd-namespace string Namespace in which Linkerd is installed ($LINKERD_NAMESPACE) (default "linkerd")
--verbose Turn on debug logging
Additional help topics:
linkerd alpha experimental subcommands for Linkerd
Use "linkerd [command] --help" for more information about a command.
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安装 Linkerd2 控制平面
首先，我们需要验证下集群，使用 linkerd check --pre，正常会输出如下信息：
Linkerd core checks
===================
kubernetes-api
--------------
√ can initialize the client
√ can query the Kubernetes API
kubernetes-version
------------------
√ is running the minimum Kubernetes API version
√ is running the minimum kubectl version
pre-kubernetes-setup
--------------------
√ control plane namespace does not already exist
√ can create non-namespaced resources
√ can create ServiceAccounts
√ can create Services
√ can create Deployments
√ can create CronJobs
√ can create ConfigMaps
√ can create Secrets
√ can read Secrets
√ can read extension-apiserver-authentication configmap
√ no clock skew detected
pre-kubernetes-capability
-------------------------
√ has NET_ADMIN capability
√ has NET_RAW capability
linkerd-version
---------------
√ can determine the latest version
√ cli is up-to-date
Status check results are √
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部署控制平面：
linkerd install | kubectl apply -f -
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查看 linkerd 命名空间的 pod 部署情况：
kubectl get po -n linkerd
NAME READY STATUS RESTARTS AGE
linkerd-destination-6c6bf4fc4-282gd 3/3 Running 0 5m
linkerd-identity-7cd9998969-cvzc8 2/2 Running 0 5m
linkerd-proxy-injector-855b9b6747-r8pcz 2/2 Running 0 5m
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同样，我们使用 linkerd check 检查一下。
ok, 接下来我们部署一些常用的扩展，增强我们控制平面的功能。
安装 Linkerd2 控制平面常用扩展
grafana，prometheus，jaeger 等的部署(针对 Linkerd 2 的相关指标)
使用如下命令：
linkerd viz install | kubectl apply -f - # on-cluster metrics stack
kubectl get po -n linkerd-viz #审查 namespace, 直到所 pod 都 ready
# grafana-5659477d88-txq5b 0/2 PodInitializing 0 14m
# metrics-api-6fcb849dc-k9sw5 2/2 Running 0 14m
# prometheus-798d8d4698-4x8h2 2/2 Running 0 14m
# tap-f5984d7f7-fkpf9 0/2 PodInitializing 0 14m
# tap-injector-6b455dd64b-2c82n 0/2 PodInitializing 0 14m
# web-657dbffb8f-7d2gr 0/2 PodInitializing 0 14m
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如果出现某一个 pod 出现错误，我们可以通过 kubectl describe po 来获取详细错误信息，如：
kubectl describe po grafana-5659477d88-txq5b -n linkerd-viz
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比如说，我这里如下镜像就被卡住了(腾讯云)：
cr.l5d.io/linkerd/grafana:edge-21.6.1
cr.l5d.io/linkerd/tap:edge-21.6.1
cr.l5d.io/linkerd/web:edge-21.6.1
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大家可以(科学上网)手动拉取。
同样，我们再部署两个可选的扩展。
部署 jaeger：
## optional
linkerd jaeger install | kubectl apply -f - # Jaeger collector and UI
kubectl get po -n linkerd-jaeger #审查 namespace
# OR:
# docker pull cr.l5d.io/linkerd/jaeger-webhook:edge-21.6.1
# docker pull jaegertracing/all-in-one:1.19.2
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部署 multicluster：
linkerd multicluster install | kubectl apply -f - # multi-cluster components
kubectl get po -n linkerd-multicluster
# 果然报错了
linkerd-gateway-bcb5888c5-ws6wz 1/2 ErrImagePull 0 21s
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查看报错信息：
kubectl describe po linkerd-gateway-bcb5888c5-ws6wz -n linkerd-multicluster
# Normal BackOff 21s (x5 over 2m13s) kubelet, k8s-master-01 Back-off pulling image "gcr.io/google_containers/pause"
# Warning Failed 21s (x5 over 2m13s) kubelet, k8s-master-01 Error: ImagePullBackOff
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很明显(gcr.io/google_containers/pause)，我们需要科学上网(具体怎么做，太多教程了，这里不讨论)。
还有一个问题比较棘手的是，这里即使 gcr.io/google_containers/pause 已经存在于本地，部署时还是回去 gcr.io 拉取。
所以，下面提供另一种方式来弄(没连外网的情况下)。
使用 kustomize 解决 linkerd-gateway (腾讯云部署)不成功的问题
kustomize 如何安装，大家自行查看 https://kustomize.io。
首先，导出 linkerd multicluster 部署 yaml 档。
linkerd multicluster install > linkerd-multicluster.yaml
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然后，我们给它打个补丁patch-linkerd-multicluster.yaml：
apiVersion: apps/v1
kind: Deployment
metadata:
annotations:
linkerd.io/created-by: linkerd/cli edge-21.6.1
labels:
app.kubernetes.io/name: gateway
app.kubernetes.io/part-of: Linkerd
app.kubernetes.io/version: edge-21.6.1
linkerd.io/control-plane-component: gateway
app: linkerd-gateway
linkerd.io/extension: multicluster
name: linkerd-gateway
namespace: linkerd-multicluster
spec:
replicas: 1
selector:
matchLabels:
app: linkerd-gateway
template:
metadata:
annotations:
linkerd.io/created-by: linkerd/cli edge-21.6.1
linkerd.io/inject: enabled
config.linkerd.io/proxy-require-identity-inbound-ports: "4191,4143"
config.linkerd.io/enable-gateway: "true"
labels:
app: linkerd-gateway
spec:
containers:
- name: pause
image: ccr.ccs.tencentyun.com/cloud-native/google-pause
serviceAccountName: linkerd-gateway
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ccr.ccs.tencentyun.com/cloud-native/google-pause，这是笔者上传到腾讯云的公开镜像。
新建 kustomization.yaml：
resources:
- linkerd-multicluster.yaml
patchesStrategicMerge:
- patch-linkerd-multicluster.yaml
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使用 kustomize 重新部署：
kustomize build . | kubectl apply -f -
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重新查看一下：
kubectl get po -n linkerd-multicluster
# linkerd-gateway-6c8dc7bb49-6tghc 2/2 Running 0 92s
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完美解决。
使用 Traefik Ingressroute 导出 linkerd-web 管理面板
关于 traefik v2 的部署，这里不做赘述。
使用 kustomize 对 linkerd viz 部署进行更新
我这里使用的域名是 linkerd-web.hacker-linner.com。
导出 yaml 档：
linkerd viz install > linkerd-viz.yaml
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打补丁，patch-linkerd-viz-web.yaml：
apiVersion: apps/v1
kind: Deployment
metadata:
annotations:
linkerd.io/created-by: linkerd/helm edge-21.6.1
labels:
linkerd.io/extension: viz
app.kubernetes.io/name: web
app.kubernetes.io/part-of: Linkerd
app.kubernetes.io/version: edge-21.6.1
component: web
namespace: linkerd-viz
name: web
namespace: linkerd-viz
spec:
replicas: 1
selector:
matchLabels:
linkerd.io/extension: viz
component: web
namespace: linkerd-viz
template:
metadata:
annotations:
linkerd.io/created-by: linkerd/helm edge-21.6.1
labels:
linkerd.io/extension: viz
component: web
namespace: linkerd-viz
spec:
nodeSelector:
beta.kubernetes.io/os: linux
containers:
- args:
- -linkerd-metrics-api-addr=metrics-api.linkerd-viz.svc.cluster.local:8085
- -cluster-domain=cluster.local
- -grafana-addr=grafana.linkerd-viz.svc.cluster.local:3000
- -controller-namespace=linkerd
- -viz-namespace=linkerd-viz
- -log-level=info
- -enforced-host=^(linkerd-web\.hacker-linner\.com|localhost|127\.0\.0\.1|web\.linkerd-viz\.svc\.cluster\.local|web\.linkerd-viz\.svc|\[::1\])(:\d+)?$
image: cr.l5d.io/linkerd/web:edge-21.6.1
imagePullPolicy: IfNotPresent
livenessProbe:
httpGet:
path: /ping
port: 9994
initialDelaySeconds: 10
name: web
ports:
- containerPort: 8084
name: http
- containerPort: 9994
name: admin-http
readinessProbe:
failureThreshold: 7
httpGet:
path: /ready
port: 9994
resources:
securityContext:
runAsUser: 2103
serviceAccountName: web
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更新 kustomization.yaml：
resources:
- linkerd-viz.yaml
- linkerd-multicluster.yaml
patchesStrategicMerge:
- patch-linkerd-viz-web.yaml
- patch-linkerd-multicluster.yaml
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重新部署
kustomize build . | kubectl apply -f -
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设置 Ingressroute & Basic Auth
ingressroute-viz.yaml
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apiVersion: v1
kind: Secret
metadata:
name: linkerd-authsecret
namespace: linkerd-viz
type: Opaque
stringData:
users: # 这里使用 htpasswd -nb 进行设置
---
apiVersion: traefik.containo.us/v1alpha1
kind: Middleware
metadata:
name: linkerd-basic-auth
namespace: linkerd-viz
spec:
basicAuth:
secret: linkerd-authsecret
---
apiVersion: traefik.containo.us/v1alpha1
kind: Middleware
metadata:
name: l5d-header-middleware
namespace: linkerd-viz
spec:
headers:
customRequestHeaders:
l5d-dst-override: "web.linkerd-viz.svc.cluster.local:8084"
---
apiVersion: traefik.containo.us/v1alpha1
kind: IngressRoute
metadata:
name: linkerd-web-ingress-route
namespace: linkerd-viz
spec:
entryPoints:
- websecure
tls:
secretName: hacker-linner-cert-tls
routes:
- match: Host(`linkerd-web.hacker-linner.com`)
kind: Rule
services:
- name: web
port: 8084
middlewares:
- name: l5d-header-middleware
- name: linkerd-basic-auth
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部署：
kubectl apply -f ingressroute-viz.yaml
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部署 emojivoto
运行如下命令：
curl -sL https://run.linkerd.io/emojivoto.yml \
| kubectl apply -f
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审查部署：
kubectl get po -n emojivoto
# OR
# docker pull docker.l5d.io/buoyantio/emojivoto-emoji-svc:v11
# docker pull docker.l5d.io/buoyantio/emojivoto-web:v11
# docker pull docker.l5d.io/buoyantio/emojivoto-voting-svc:v11
emoji-6b776684f5-nnflg 1/1 Running 0 6m4s
vote-bot-64695c4dc6-jn8ln 1/1 Running 0 6m4s
voting-7778876bdb-kdvsx 1/1 Running 0 6m4s
web-6f8d774656-9dsw7 1/1 Running 0 6m4s
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设置 Ingressroute
这里是：https://emojivoto.hacker-linner.com
emojivoto-ingressroute.yaml
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apiVersion: traefik.containo.us/v1alpha1
kind: IngressRoute
metadata:
name: emojivoto-web-ingress-route
namespace: emojivoto
spec:
entryPoints:
- websecure
tls:
secretName: hacker-linner-cert-tls
routes:
- match: Host(`emojivoto.hacker-linner.com`)
kind: Rule
services:
- name: web-svc
port: 80
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Service Mesh(Linkerd) 注入
添加 Linkerd 到 emojivoto：
kubectl get -n emojivoto deploy -o yaml \
| linkerd inject - \
| kubectl apply -f -
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审查一下是否一切正常：
linkerd -n emojivoto check --proxy
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回到面板查看 emojivoto：
完美搞定，一切正常。
最后看一下 Grafana 面板：
Refs
- What's a service mesh? And why do I need one?
- https://buoyant.io/2020/10/12/what-is-a-service-mesh
- 快速上手 Linkerd v2 Service Mesh(服务网格)
- Getting Started
- https://linkerd.io/2.10/getting-started
