vL3 load balancer example (#9830)

* vL3 load balancer example

Signed-off-by: Artem Glazychev <[email protected]>

* Ref

Signed-off-by: Artem Glazychev <[email protected]>

---------

Signed-off-by: Artem Glazychev <[email protected]>

apps/vl3-lb/kustomization.yaml

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+---
+apiVersion: kustomize.config.k8s.io/v1beta1
+kind: Kustomization
+
+resources:
+- lb.yaml

apps/vl3-lb/lb.yaml

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+---
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: vl3-lb
+spec:
+  selector:
+    matchLabels:
+      app: vl3-lb
+  template:
+    metadata:
+      labels:
+        app: vl3-lb
+        "spiffe.io/spiffe-id": "true"
+    spec:
+      containers:
+        - name: lb
+          image: ghcr.io/networkservicemesh/ci/cmd-lb-vl3-vpp:cd64380
+          imagePullPolicy: IfNotPresent
+          env:
+            - name: SPIFFE_ENDPOINT_SOCKET
+              value: unix:///run/spire/sockets/agent.sock
+            - name: NSM_NAME
+              valueFrom:
+                fieldRef:
+                  fieldPath: metadata.name
+            - name: POD_NAME
+              value: "$(NSM_NAME)"
+            - name: NSM_PORT
+              value: "80"
+            - name: NSM_LOG_LEVEL
+              value: TRACE
+          volumeMounts:
+            - name: spire-agent-socket
+              mountPath: /run/spire/sockets
+              readOnly: true
+            - name: nsm-socket
+              mountPath: /var/lib/networkservicemesh
+              readOnly: true
+          resources:
+            requests:
+              cpu: 150m
+              memory: 100Mi
+            limits:
+              cpu: 300m
+              memory: 300Mi
+      volumes:
+        - name: spire-agent-socket
+          hostPath:
+            path: /run/spire/sockets
+            type: Directory
+        - name: nsm-socket
+          hostPath:
+            path: /var/lib/networkservicemesh
+            type: DirectoryOrCreate

examples/features/vl3-lb/README.md

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+# vL3 Load Balancer
+
+This example shows what is a vL3 Load Balancer (LB) and how it works.
+
+## Description
+
+We all know and use Kubernetes Services in our work. 
+Service is a method for exposing a network application that is running as one or more Pods in your cluster. It distributes traffic across a set of selected Pods.
+
+To define a Kubernetes Service:
+```
+apiVersion: v1
+kind: Service
+metadata:
+  name: my-service
+spec:
+  selector:
+    app.kubernetes.io/name: MyApp
+  ports:
+    - protocol: TCP
+      port: 80
+      targetPort: 9376
+```
+Now you can reach the service by its name.
+
+It turned out that we can use a similar mechanism in our vL3 networks - we can use a **vL3 Load Balancer**.
+Being on the same vL3 network, clients can behave like pods - they can communicate with each other. Using selectors, we can combine some of them to implement a service.
+vL3-LB will help us with this. We will call these clients that implement the service as _"real servers"_.
+
+So, vL3-LB has the following parameters:
+
+| NSM env            | Description                                                        |
+|--------------------|--------------------------------------------------------------------|
+| `NSM_SELECTOR`     | labels that group the vL3 clients we need to implement any service |
+| `NSM_PROTOCOL`     | TCP or UDP IP protocol                                             |
+| `NSM_PORT`         | LB port                                                            |
+| `NSM_TARGET_PORT`  | real server port                                                   |
+
+vL3-LB is a vL3-network client that monitors the real servers using `NSM_SELECTOR`. It has its own DNS name that we can use.<br />
+
+**Example of monitoring:**
+
+![NSM vL3 Diagram](./diagram1.svg "vL3-LB monitoring")
+<br />_Please note: The network configuration is given as an example. It can have a different number of elements._
+<br /><br />
+In the current example, we want to get a _finance_ service for processing **http requests**. <br />
+After calling the command `$:curl finance:8080`, the DNS name is converted to the IP address of the Load Balancer. <br />
+When the http request reaches the balancer, it converts the destination address to the address of the real server.
+
+**Example of the data path:**<br />
+
+![NSM vL3 Diagram](./diagram2.svg "vL3-LB data path")
+<br />_Please note: The IP addresses are given as an example, they may change from run to run._
+
+## Run
+
+Deploy the vL3 network service, vL3-NSE, vL3-LB, finance-servers and finance-client (the last 3 are actually clients of the vL3 network) (see `kustomization.yaml`):
+```bash
+kubectl apply -k https://github.com/networkservicemesh/deployments-k8s/examples/features/vl3-lb?ref=fea72f963b344a0acdae636ceec6ea9f25fbfffb
+```
+
+Wait for vL3-clients to be ready:
+```bash
+kubectl wait --for=condition=ready --timeout=2m pod -l type=vl3-client -n ns-vl3-lb
+```
+
+Send an http-request from the finance-client:
+```bash
+kubectl exec deployments/finance-client -n ns-vl3-lb -- curl -s finance:8080 | grep "Hello! I'm finance-server"
+```
+In the response you will see the name of the real server that performed the processing.
+If you run the command above many times, you will see that load balancing occurs and the responses are returned by different handlers.
+
+## Cleanup
+
+To clean up the example just follow the next command:
+```bash
+kubectl delete ns ns-vl3-lb
+```

examples/features/vl3-lb/finance-client.yaml

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+---
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: finance-client
+spec:
+  replicas: 1
+  selector:
+    matchLabels:
+      app: finance-client
+  template:
+    metadata:
+      labels:
+        app: finance-client
+        type: vl3-client
+      annotations:
+        networkservicemesh.io: kernel://vl3-lb/nsm-1
+    spec:
+      containers:
+      - name: nettools
+        image: travelping/nettools:1.10.1
+        imagePullPolicy: IfNotPresent
+        # simple `sleep` command would work
+        # but we need `trap` to be able to delete pods quckly
+        command: ["/bin/sh", "-c", "trap : TERM INT; sleep infinity & wait"]

examples/features/vl3-lb/finance-lb-patch.yaml

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+---
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: vl3-lb
+spec:
+  template:
+    metadata:
+      labels:
+        type: vl3-client
+    spec:
+      containers:
+        - name: lb
+          env:
+            - name: POD_NAME
+              value: "finance"
+            - name: NSM_PORT
+              value: "8080"
+            - name: NSM_TARGET_PORT
+              value: "80"
+            - name: NSM_SELECTOR
+              value: "app:finance"
+            - name: NSM_NETWORK_SERVICES
+              value: "memif://vl3-lb/nsm-1"

examples/features/vl3-lb/finance-server.yaml

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+---
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: finance-server
+spec:
+  replicas: 3
+  selector:
+    matchLabels:
+      app: finance-server
+  template:
+    metadata:
+      labels:
+        app: finance-server
+        type: vl3-client
+      annotations:
+        networkservicemesh.io: kernel://vl3-lb/nsm-1?app=finance
+    spec:
+      containers:
+        - name: nginx
+          image: hashicorp/http-echo:alpine
+          env:
+          - name: POD_NAME
+            valueFrom:
+              fieldRef:
+                fieldPath: metadata.name
+          args:
+            - "-text=Hello! I'm $(POD_NAME)"
+            - -listen=:80
+          ports:
+            - containerPort: 80

examples/features/vl3-lb/kustomization.yaml

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+---
+apiVersion: kustomize.config.k8s.io/v1beta1
+kind: Kustomization
+
+namespace: ns-vl3-lb
+
+resources:
+- ns-vl3-lb.yaml
+- netsvc.yaml
+- finance-client.yaml
+- finance-server.yaml
+- ../../../apps/nse-vl3-vpp
+- ../../../apps/vl3-ipam
+- ../../../apps/vl3-lb
+
+patchesStrategicMerge:
+- nse-patch.yaml
+- finance-lb-patch.yaml

examples/features/vl3-lb/netsvc.yaml

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+---
+apiVersion: networkservicemesh.io/v1
+kind: NetworkService
+metadata:
+  name: vl3-lb
+spec:
+  payload: IP

examples/features/vl3-lb/ns-vl3-lb.yaml

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+---
+apiVersion: v1
+kind: Namespace
+metadata:
+  name: ns-vl3-lb

examples/features/vl3-lb/nse-patch.yaml

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+---
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: nse-vl3-vpp
+  labels:
+    app: nse-vl3-vpp
+spec:
+  replicas: 1
+  template:
+    spec:
+      containers:
+        - name: nse
+          env:
+            - name: NSM_SERVICE_NAMES
+              value: "vl3-lb"
+            - name: NSM_REGISTER_SERVICE
+              value: "false"