Мікросервісна архітектура · fullstack.org.ua

fullstack.org.ua

Мікросервісна архітектура · fullstack.org.ua

text

Клієнт → API Gateway
             ├── Orders → база замовлень
             ├── Payments → база платежів
             └── Inventory → база залишків

javascript

const http = require("node:http");

const role = process.env.ROLE || "orders";
const port = Number(process.env.PORT || (role === "inventory" ? 3001 : 3000));
const inventoryUrl = process.env.INVENTORY_URL || "http://localhost:3001";

let stock = 10;
const orders = [];

function sendJson(response, statusCode, body) {
  response.writeHead(statusCode, {
    "Content-Type": "application/json; charset=utf-8",
  });
  response.end(JSON.stringify(body));
}

function readJson(request) {
  return new Promise((resolve, reject) => {
    let data = "";

    request.on("data", (chunk) => {
      data += chunk;

      if (data.length > 1_000_000) {
        reject(new Error("Занадто великий запит"));
        request.destroy();
      }
    });

    request.on("end", () => {
      try {
        resolve(data ? JSON.parse(data) : {});
      } catch {
        reject(new Error("Некоректний JSON"));
      }
    });

    request.on("error", reject);
  });
}

async function reserveProduct(productId, quantity) {
  const controller = new AbortController();
  const timeout = setTimeout(() => controller.abort(), 2000);

  try {
    const response = await fetch(`${inventoryUrl}/reserve`, {
      method: "POST",
      headers: {
        "Content-Type": "application/json",
      },
      body: JSON.stringify({ productId, quantity }),
      signal: controller.signal,
    });

    const body = await response.json();

    if (!response.ok) {
      throw new Error(body.error || "Не вдалося зарезервувати товар");
    }

    return body;
  } finally {
    clearTimeout(timeout);
  }
}

const server = http.createServer(async (request, response) => {
  try {
    if (role === "inventory" && request.method === "POST" && request.url === "/reserve") {
      const { productId, quantity } = await readJson(request);

      if (!productId || !Number.isInteger(quantity) || quantity <= 0) {
        return sendJson(response, 400, {
          error: "productId і додатна ціла quantity є обов'язковими",
        });
      }

      if (quantity > stock) {
        return sendJson(response, 409, {
          error: "Недостатньо товару на складі",
          available: stock,
        });
      }

      stock -= quantity;

      return sendJson(response, 200, {
        productId,
        reserved: quantity,
        remaining: stock,
      });
    }

    if (role === "orders" && request.method === "POST" && request.url === "/orders") {
      const { productId, quantity } = await readJson(request);

      if (!productId || !Number.isInteger(quantity) || quantity <= 0) {
        return sendJson(response, 400, {
          error: "productId і додатна ціла quantity є обов'язковими",
        });
      }

      let reservation;

      try {
        reservation = await reserveProduct(productId, quantity);
      } catch (error) {
        return sendJson(response, 503, {
          error: "Сервіс складу тимчасово недоступний",
          details: error.name === "AbortError" ? "Тайм-аут" : error.message,
        });
      }

      const order = {
        id: String(orders.length + 1),
        productId,
        quantity,
        status: "created",
        reservation,
      };

      orders.push(order);

      return sendJson(response, 201, order);
    }

    if (request.method === "GET" && request.url === "/health") {
      return sendJson(response, 200, {
        service: role,
        status: "ok",
      });
    }

    sendJson(response, 404, { error: "Маршрут не знайдено" });
  } catch (error) {
    sendJson(response, 500, {
      error: error.message || "Внутрішня помилка",
    });
  }
});

server.listen(port, () => {
  console.log(`${role} service is running on port ${port}`);
});