Deploying C++ on Kubernetes: A Basic Practical Guide

Deploying C++ on Kubernetes: A Basic Practical Guide

Kubernetes (K8s) has become the de facto standard for container orchestration. Although it is most often associated with Go, Java, or Python, C++ is also actively used for high-load services where performance and low memory consumption are critical. In this article, we will walk through the practical process of deploying a C++ application in a Kubernetes cluster: from writing a simple HTTP server to creating manifests and scaling.

1. Preparing the C++ Application and Docker Image

First, let's create a minimal C++ application that will listen for HTTP requests. We'll use the cpp-httplib library (header-only) for simplicity.

Source Code (server.cpp)

#include <httplib.h>#include <iostream>

int main() {    using namespace httplib;    Server svr;

    svr.Get("/", [](const Request& req, Response& res) {        res.set_content("Hello from C++ on Kubernetes!", "text/plain");    });

    svr.Get("/health", [](const Request& req, Response& res) {        res.set_content("OK", "text/plain");    });

    std::cout << "Server started on port 8080" << std::endl;    svr.listen("0.0.0.0", 8080);    return 0;}

Dockerfile (Multi-stage Build)

To keep the image compact and secure, we use a multi-stage build:

# Build stageFROM gcc:13-bookworm AS builderWORKDIR /appCOPY server.cpp .RUN g++ -std=c++17 -O2 -lpthread server.cpp -o server

# Final imageFROM debian:bookworm-slimWORKDIR /appCOPY --from=builder /app/server .EXPOSE 8080CMD ["./server"]

Build the image:

docker build -t cpp-k8s-demo:latest .

Test it locally:

docker run -p 8080:8080 cpp-k8s-democurl http://localhost:8080/

2. Writing Kubernetes Manifests

For deployment, we will need two main resources: Deployment (managing pods) and Service (network access).

Deployment (deployment.yaml)

Defines how many replicas to run, the update policy, and the container image.

apiVersion: apps/v1kind: Deploymentmetadata:  name: cpp-app-deployment  labels:    app: cpp-appspec:  replicas: 3  selector:    matchLabels:      app: cpp-app  template:    metadata:      labels:        app: cpp-app    spec:      containers:      - name: cpp-app        image: cpp-k8s-demo:latest        imagePullPolicy: IfNotPresent        ports:        - containerPort: 8080        livenessProbe:          httpGet:            path: /health            port: 8080          initialDelaySeconds: 5          periodSeconds: 10        resources:          requests:            memory: "64Mi"            cpu: "100m"          limits:            memory: "128Mi"            cpu: "200m"

Important: imagePullPolicy: IfNotPresent is suitable for local testing. For production, use Always or specify a version tag.

Service (service.yaml)

Provides access to the pods inside the cluster (ClusterIP) or externally (NodePort/LoadBalancer).

apiVersion: v1kind: Servicemetadata:  name: cpp-app-servicespec:  selector:    app: cpp-app  ports:  - protocol: TCP    port: 80    targetPort: 8080  type: LoadBalancer

3. Deploying to the Cluster and Verification

Assume you already have a running cluster (Minikube, kind, or cloud-based). Execute the commands:

# Load the image into the cluster (for Minikube)minikube image load cpp-k8s-demo:latest

# Apply the manifestskubectl apply -f deployment.yamlkubectl apply -f service.yaml

# Check the statuskubectl get pods -l app=cpp-appkubectl get svc cpp-app-service

                
                

                    

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