Deploying C++ on Kubernetes: A Basic Guide for Beginners

Introduction: Why Deploy C++ in Kubernetes?

C++ remains one of the most performant programming languages, especially in the areas of high-load systems, game servers, financial applications, and IoT. However, in the modern world of cloud technologies, simply writing fast code is not enough — you need to be able to reliably deploy, scale, and update it without downtime. This is where Kubernetes (K8s) comes to the rescue — a container orchestration system that automates the deployment, scaling, and management of applications.

In this guide, we will walk through the process of deploying a simple C++ application in a Kubernetes cluster step by step. You will learn how to package C++ code into a Docker image, write the necessary Kubernetes manifests, and run your application in the cloud. The article is aimed at beginners, so we will not delve into complex configurations, but will focus on a basic, yet working pipeline.

1. Preparation: C++ Application and Docker Containerization

Before talking about Kubernetes, we need to prepare our C++ application to work in a container. Containerization is packaging an application together with all its dependencies into an isolated environment. For C++, this is critically important, as a compiled binary may depend on specific versions of libraries (libc, libstdc++, etc.) on the target machine.

1.1. Simple C++ Application for Deployment

Let's create a file main.cpp — a simple HTTP server that will respond to requests. For simplicity, we will not use external libraries, but write a primitive TCP server.

// main.cpp\n#include <iostream>\n#include <string>\n#include <cstring>\n#include <sys/socket.h>\n#include <netinet/in.h>\n#include <unistd.h>\n\nint main() {\n    int server_fd, new_socket;\n    struct sockaddr_in address;\n    int opt = 1;\n    int addrlen = sizeof(address);\n    char buffer[1024] = {0};\n    const char* hello = "HTTP/1.1 200 OK\\nContent-Type: text/plain\\nContent-Length: 12\\n\\nHello, K8s!\\n";\n\n    // Creating a socket\n    if ((server_fd = socket(AF_INET, SOCK_STREAM, 0)) == 0) {\n        perror("socket failed");\n        exit(EXIT_FAILURE);\n    }\n\n    // Binding to port 8080\n    if (setsockopt(server_fd, SOL_SOCKET, SO_REUSEADDR | SO_REUSEPORT, &opt, sizeof(opt))) {\n        perror("setsockopt");\n        exit(EXIT_FAILURE);\n    }\n    address.sin_family = AF_INET;\n    address.sin_addr.s_addr = INADDR_ANY;\n    address.sin_port = htons(8080);\n\n    if (bind(server_fd, (struct sockaddr *)&address, sizeof(address))<0) {\n        perror("bind failed");\n        exit(EXIT_FAILURE);\n    }\n\n    if (listen(server_fd, 3) < 0) {\n        perror("listen");\n        exit(EXIT_FAILURE);\n    }\n\n    std::cout << "Server listening on port 8080" << std::endl;\n\n    while(true) {\n        if ((new_socket = accept(server_fd, (struct sockaddr *)&address, (socklen_t*)&addrlen))<0) {\n            perror("accept");\n            exit(EXIT_FAILURE);\n        }\n        read(new_socket, buffer, 1024);\n        send(new_socket, hello, strlen(hello), 0);\n        close(new_socket);\n    }\n    return 0;\n}\n

1.2. Building a Static Binary

To make our container minimal and independent of the host's system libraries, it is better to build a statically linked binary. Run the command:

g++ -static -o server main.cpp -lpthread

The -static flag includes all necessary libraries directly into the executable file. The -lpthread flag is needed for working with threads (although it is not required in our simple example, it will be useful for real projects).

1.3. Dockerfile for the C++ Application

Now let's create a Dockerfile. We will use a multi-stage build: first, compile the code in a large image with a compiler, then