linkerd-patterns

# Linkerd Patterns Production patterns for Linkerd service mesh - the lightweight, security-first service mesh for Kubernetes. ## Do not use this skill when - The task is unrelated to linkerd patterns - You need a different domain or tool outside this scope ## Instructions - Clarify goals, constraints, and required inputs. - Apply relevant best practices and validate outcomes. - Provide actionable steps and verification. - If detailed examples are required, open `resources/implementation-playbook.md`. ## Use this skill when - Setting up a lightweight service mesh - Implementing automatic mTLS - Configuring traffic splits for canary deployments - Setting up service profiles for per-route metrics - Implementing retries and timeouts - Multi-cluster service mesh ## Core Concepts ### 1. Linkerd Architecture ``` ┌─────────────────────────────────────────────┐ │ Control Plane │ │ ┌─────────┐ ┌──────────┐ ┌──────────────┐ │ │ │ destiny │ │ identity │ │ proxy-inject │ │ │ └─────────┘ └──────────┘ └──────────────┘ │ └─────────────────────────────────────────────┘ │ ┌─────────────────────────────────────────────┐ │ Data Plane │ │ ┌─────┐ ┌─────┐ ┌─────┐ │ │ │proxy│────│proxy│────│proxy│ │ │ └─────┘ └─────┘ └─────┘ │ │ │ │ │ │ │ ┌──┴──┐ ┌──┴──┐ ┌──┴──┐ │ │ │ app │ │ app │ │ app │ │ │ └─────┘ └─────┘ └─────┘ │ └─────────────────────────────────────────────┘ ``` ### 2. Key Resources | Resource | Purpose | |----------|---------| | **ServiceProfile** | Per-route metrics, retries, timeouts | | **TrafficSplit** | Canary deployments, A/B testing | | **Server** | Define server-side policies | | **ServerAuthorization** | Access control policies | ## Templates ### Template 1: Mesh Installation ```bash # Install CLI brew install linkerd # Alternative: download the official installer, inspect it, then execute it curl --proto '=https' --tlsv1.2 -sSfL https://run.linkerd.io/install -o /tmp/linkerd-install.sh sed -n '1,160p' /tmp/linkerd-install.sh sh /tmp/linkerd-install.sh # Validate cluster linkerd check --pre # Install CRDs linkerd install --crds | kubectl apply -f - # Install control plane linkerd install | kubectl apply -f - # Verify installation linkerd check # Install viz extension (optional) linkerd viz install | kubectl apply -f - ``` ### Template 2: Inject Namespace ```yaml # Automatic injection for namespace apiVersion: v1 kind: Namespace metadata: name: my-app annotations: linkerd.io/inject: enabled --- # Or inject specific deployment apiVersion: apps/v1 kind: Deployment metadata: name: my-app annotations: linkerd.io/inject: enabled spec: template: metadata: annotations: linkerd.io/inject: enabled ``` ### Template 3: Service Profile with Retries ```yaml apiVersion: linkerd.io/v1alpha2 kind: ServiceProfile metadata: name: my-service.my-namespace.svc.cluster.local namespace: my-namespace spec: routes: - name: GET /api/users condition: method: GET pathRegex: /api/users responseClasses: - condition: status: min: 500 max: 599 isFailure: true isRetryable: true - name: POST /api/users condition: method: POST pathRegex: /api/users # POST not retryable by default isRetryable: false - name: GET /api/users/{id} condition: method: GET pathRegex: /api/users/[^/]+ timeout: 5s isRetryable: true retryBudget: retryRatio: 0.2 minRetriesPerSecond: 10 ttl: 10s ``` ### Template 4: Traffic Split (Canary) ```yaml apiVersion: split.smi-spec.io/v1alpha1 kind: TrafficSplit metadata: name: my-service-canary namespace: my-namespace spec: service: my-service backends: - service: my-service-stable weight: 900m # 90% - service: my-service-canary weight: 100m # 10% ``` ### Template 5: Server Authorization Policy ```yaml # Define the server apiVersion: policy.linkerd.io/v1beta1 kind: Server metadata: name: my-service-http namespace: my-namespace spec: podSelector: matchLabels: app: my-service port: http proxyProtocol: HTTP/1 --- # Allow traffic from specific clients apiVersion: policy.linkerd.io/v1beta1 kind: ServerAuthorization metadata: name: allow-frontend namespace: my-namespace spec: server: name: my-service-http client: meshTLS: serviceAccounts: - name: frontend namespace: my-namespace --- # Allow unauthenticated traffic (e.g., from ingress) apiVersion: policy.linkerd.io/v1beta1 kind: ServerAuthorization metadata: name: allow-ingress namespace: my-namespace spec: server: name: my-service-http client: unauthenticated: true networks: - cidr: 10.0.0.0/8 ``` ### Template 6: HTTPRoute for Advanced Routing ```yaml apiVersion: policy.linkerd.io/v1beta2 kind: HTTPRoute metadata: name: my-route namespace: my-namespace spec: parentRefs: - name: my-service kind: Service group: core port: 8080 rules: - matches: - path: type: PathPrefix value: /api/v2 - headers: - name: x-api-version value: v2 backendRefs: - name: my-service-v2 port: 8080 - matches: - path: type: PathPrefix value: /api backendRefs: - name: my-service-v1 port: 8080 ``` ### Template 7: Multi-cluster Setup ```bash # On each cluster, install with cluster credentials linkerd multicluster install | kubectl apply -f - # Link clusters linkerd multicluster link --cluster-name west \ --api-server-address https://west.example.com:6443 \ | kubectl apply -f - # Export a service to other clusters kubectl label svc/my-service mirror.linkerd.io/exported=true # Verify cross-cluster connectivity linkerd multicluster check linkerd multicluster gateways ``` ## Monitoring Commands ```bash # Live traffic view linkerd viz top deploy/my-app # Per-route metrics linkerd viz routes deploy/my-app # Check proxy status linkerd viz stat deploy -n my-namespace # View service dependencies linkerd viz edges deploy -n my-namespace # Dashboard linkerd viz dashboard ``` ## Debugging ```bash # Check injection status linkerd check --proxy -n my-namespace # View proxy logs kubectl logs deploy/my-app -c linkerd-proxy # Debug identity/TLS linkerd identity -n my-namespace # Tap traffic (live) linkerd viz tap deploy/my-app --to deploy/my-backend ``` ## Best Practices ### Do's - **Enable mTLS everywhere** - It's automatic with Linkerd - **Use ServiceProfiles** - Get per-route metrics and retries - **Set retry budgets** - Prevent retry storms - **Monitor golden metrics** - Success rate, latency, throughput ### Don'ts - **Don't skip check** - Always run `linkerd check` after changes - **Don't over-configure** - Linkerd defaults are sensible - **Don't ignore ServiceProfiles** - They unlock advanced features - **Don't forget timeouts** - Set appropriate values per route ## Resources - [Linkerd Documentation](https://linkerd.io/2.14/overview/) - [Service Profiles](https://linkerd.io/2.14/features/service-profiles/) - [Authorization Policy](https://linkerd.io/2.14/features/server-policy/) ## Limitations - Use this skill only when the task clearly matches the scope described above. - Do not treat the output as a substitute for environment-specific validation, testing, or expert review. - Stop and ask for clarification if required inputs, permissions, safety boundaries, or success criteria are missing.