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HTTP Traffic Splitting (nginx#261)
Support Backend Weight This commit adds support for the BackendRef Weight field which enables traffic splitting use cases. Traffic splitting in the data plane is implemented using the nginx split_clients directive. A split_clients directive is generated for every attached HTTPRoute rule that has multiple backendRefs defined.
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‎README.md

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NGINX Kubernetes Gateway is an open-source project that provides an implementation of the [Gateway API](https://gateway-api.sigs.k8s.io/) using [NGINX](https://nginx.org/) as the data plane. The goal of this project is to implement the core Gateway APIs -- `Gateway`, `GatewayClass`, `HTTPRoute`, `TCPRoute`, `TLSRoute`, and `UDPRoute` -- to configure an HTTP or TCP/UDP load balancer, reverse-proxy, or API gateway for applications running on Kubernetes. NGINX Kubernetes Gateway is currently under development and supports a subset of the Gateway API.
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For a list of supported Gateway API resources and features, see the [Gateway API Compatibility](docs/gateway-api-compatibility.md.md) doc.
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For a list of supported Gateway API resources and features, see the [Gateway API Compatibility](docs/gateway-api-compatibility.md) doc.
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> Warning: This project is actively in development (beta feature state) and should not be deployed in a production environment.
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> All APIs, SDKs, designs, and packages are subject to change.

‎deploy/manifests/nginx-gateway.yaml

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volumes:
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- name: nginx-config
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emptyDir: { }
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- name: var-lib-nginx
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emptyDir: { }
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- name: njs-modules
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configMap:
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name: njs-modules
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volumeMounts:
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- name: nginx-config
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mountPath: /etc/nginx
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- name: var-lib-nginx
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mountPath: /var/lib/nginx
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- name: njs-modules
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mountPath: /usr/lib/nginx/modules/njs

‎docs/gateway-api-compatibility.md.md renamed to ‎docs/gateway-api-compatibility.md

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* `type` - supported.
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* `requestRedirect` - supported except for the experimental `path` field. If multiple filters with `requestRedirect` are configured, NGINX Kubernetes Gateway will choose the first one and ignore the rest.
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* `requestHeaderModifier`, `requestMirror`, `urlRewrite`, `extensionRef` - not supported.
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* `backendRefs` - partially supported. Only a single backend ref without support for `weight`. Backend ref `filters` are not supported.
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* `backendRefs` - partially supported. Backend ref `filters` are not supported.
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* `status`
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* `parents`
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* `parentRef` - supported.

‎examples/traffic-splitting/README.md

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# Example
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In this example we will deploy NGINX Kubernetes Gateway and configure traffic splitting for a simple cafe application.
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We will use `HTTPRoute` resources to split traffic between two versions of the application -- `coffee-v1` and `coffee-v2`.
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## Running the Example
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## 1. Deploy NGINX Kubernetes Gateway
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1. Follow the [installation instructions](/docs/installation.md) to deploy NGINX Gateway.
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1. Save the public IP address of NGINX Kubernetes Gateway into a shell variable:
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```
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GW_IP=XXX.YYY.ZZZ.III
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```
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1. Save the port of NGINX Kubernetes Gateway:
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```
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GW_PORT=<port number>
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```
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## 2. Deploy the Coffee Application
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1. Create the Cafe Deployments and Services:
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```
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kubectl apply -f cafe.yaml
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```
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1. Check that the Pods are running in the `default` namespace:
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```
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kubectl -n default get pods
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NAME READY STATUS RESTARTS AGE
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coffee-v1-7c57c576b-rfjsh 1/1 Running 0 21m
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coffee-v2-698f66dc46-vcb6r 1/1 Running 0 21m
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```
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## 3. Configure Routing
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1. Create the `Gateway`:
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```
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kubectl apply -f gateway.yaml
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```
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1. Create the `HTTPRoute` resources:
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```
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kubectl apply -f cafe-route.yaml
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```
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This `HTTPRoute` resource defines a route for the path `/coffee` that sends 80% of the requests to `coffee-v1` and 20% to `coffee-v2`.
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In this example, we use 80 and 20; however, the weights are calculated proportionally and do not need to sum to 100.
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For example, the weights of 8 and 2, 16 and 4, or 32 and 8 all evaluate to the same relative proportions.
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## 4. Test the Application
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To access the application, we will use `curl` to send requests to `/coffee`:
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```
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curl --resolve cafe.example.com:$GW_PORT:$GW_IP http://cafe.example.com:$GW_PORT/coffee
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```
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80% of the responses will come from `coffee-v1`:
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```
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Server address: 10.12.0.18:80
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Server name: coffee-v1-7c57c576b-rfjsh
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```
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20% of the responses will come from `coffee-v2`:
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```
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Server address: 10.12.0.19:80
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Server name: coffee-v2-698f66dc46-vcb6r
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```
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### 5. Modify the Traffic Split Configuration
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Let's shift more of the traffic to `coffee-v2`. To do this we will update the `HTTPRoute` resource and change the weight
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of the `coffee-v2` backend to 80. Backends with equal weights will receive an equal share of traffic.
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1. Apply the updated `HTTPRoute` resource:
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```
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kubectl apply -f cafe-route-equal-weight.yaml
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```
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2. Test the application again:
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```
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curl --resolve cafe.example.com:$GW_PORT:$GW_IP http://cafe.example.com:$GW_PORT/coffee
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```
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The responses will now be split evenly between `coffee-v1` and `coffee-v2`.
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We can continue modifying the weights of the backends to shift more and more traffic to `coffee-v2`. If there's an issue
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with `coffee-v2`, we can quickly shift traffic back to `coffee-v1`.

‎examples/traffic-splitting/cafe-route-equal-weight.yaml

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apiVersion: gateway.networking.k8s.io/v1beta1
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kind: HTTPRoute
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metadata:
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name: cafe-route
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spec:
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parentRefs:
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- name: gateway
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sectionName: http
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hostnames:
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- "cafe.example.com"
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rules:
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- matches:
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- path:
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type: PathPrefix
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value: /coffee
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backendRefs:
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- name: coffee-v1
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port: 80
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weight: 80
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- name: coffee-v2
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port: 80
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weight: 80

‎examples/traffic-splitting/cafe-route.yaml

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apiVersion: gateway.networking.k8s.io/v1beta1
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kind: HTTPRoute
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metadata:
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name: cafe-route
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spec:
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parentRefs:
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- name: gateway
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sectionName: http
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hostnames:
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- "cafe.example.com"
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rules:
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- matches:
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- path:
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type: PathPrefix
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value: /coffee
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backendRefs:
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- name: coffee-v1
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port: 80
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weight: 80
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- name: coffee-v2
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port: 80
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weight: 20

‎examples/traffic-splitting/cafe.yaml

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apiVersion: apps/v1
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kind: Deployment
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metadata:
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name: coffee-v1
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spec:
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replicas: 1
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selector:
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matchLabels:
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app: coffee-v1
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template:
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metadata:
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labels:
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app: coffee-v1
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spec:
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containers:
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- name: coffee-v1
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image: nginxdemos/nginx-hello:plain-text
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ports:
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- containerPort: 8080
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---
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apiVersion: v1
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kind: Service
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metadata:
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name: coffee-v1
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spec:
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ports:
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- port: 80
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targetPort: 8080
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protocol: TCP
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name: http
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selector:
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app: coffee-v1
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---
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apiVersion: apps/v1
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kind: Deployment
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metadata:
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name: coffee-v2
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spec:
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replicas: 1
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selector:
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matchLabels:
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app: coffee-v2
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template:
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metadata:
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labels:
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app: coffee-v2
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spec:
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containers:
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- name: coffee-v2
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image: nginxdemos/nginx-hello:plain-text
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ports:
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- containerPort: 8080
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---
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apiVersion: v1
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kind: Service
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metadata:
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name: coffee-v2
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spec:
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ports:
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- port: 80
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targetPort: 8080
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protocol: TCP
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name: http
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selector:
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app: coffee-v2

‎examples/traffic-splitting/gateway.yaml

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apiVersion: gateway.networking.k8s.io/v1beta1
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kind: Gateway
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metadata:
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name: gateway
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labels:
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domain: k8s-gateway.nginx.org
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spec:
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gatewayClassName: nginx
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listeners:
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- name: http
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port: 80
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protocol: HTTP

‎internal/nginx/config/execute.go

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package config
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import (
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"bytes"
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"text/template"
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)
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// executes the template with the given data.
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func execute(template *template.Template, data interface{}) []byte {
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var buf bytes.Buffer
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err := template.Execute(&buf, data)
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if err != nil {
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panic(err)
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}
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return buf.Bytes()
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}

‎internal/nginx/config/execute_test.go

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package config
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import (
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"testing"
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"github.com/nginxinc/nginx-kubernetes-gateway/internal/nginx/config/http"
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)
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func TestExecute(t *testing.T) {
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defer func() {
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if r := recover(); r != nil {
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t.Errorf("execute() panicked with %v", r)
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}
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}()
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bytes := execute(serversTemplate, []http.Server{})
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if len(bytes) == 0 {
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t.Error("template.execute() did not generate anything")
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}
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}
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func TestExecutePanics(t *testing.T) {
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defer func() {
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if r := recover(); r == nil {
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t.Error("template.execute() did not panic")
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}
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}()
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_ = execute(serversTemplate, "not-correct-data")
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}

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