add managing multiple docker containers with the same image files

docker-modules/managing-multiple-docker-containers-same-image-different-configs/Dockerfile

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+FROM node:24-alpine
+
+WORKDIR /app
+
+COPY app/ ./app/
+WORKDIR /app/app
+
+RUN npm init -y && npm install express
+
+EXPOSE 3000
+
+CMD ["node", "index.js"]

docker-modules/managing-multiple-docker-containers-same-image-different-configs/app/index.js

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+const express = require("express");
+const fs = require("fs");
+const path = require("path");
+
+const app = express();
+
+let config = {
+    SERVICE_NAME: process.env.SERVICE_NAME || "default-service",
+    ENVIRONMENT: process.env.ENVIRONMENT || "development",
+    LOG_LEVEL: process.env.LOG_LEVEL || "info",
+    PORT: process.env.PORT || 3000,
+};
+
+if (process.env.CONFIG_PATH) {
+    try {
+        const configPath = path.resolve(process.env.CONFIG_PATH);
+        const fileContent = fs.readFileSync(configPath, "utf-8");
+        const fileConfig = JSON.parse(fileContent);
+        config = { ...config, ...fileConfig };
+        console.log(`[INFO] Loaded config from ${configPath}`);
+    } catch (err) {
+        console.error(
+            `[ERROR] Failed to load config from ${process.env.CONFIG_PATH}:`,
+            err.message
+        );
+    }
+}
+
+console.log(
+    `[INFO] Starting ${config.SERVICE_NAME} in ${config.ENVIRONMENT} mode (log level: ${config.LOG_LEVEL})`
+);
+
+app.get("/", (req, res) => {
+    res.send(`
+    <h1>Service: ${config.SERVICE_NAME}</h1>
+    <p>Environment: ${config.ENVIRONMENT}</p>
+    <p>Log level: ${config.LOG_LEVEL}</p>
+    <p>Running on port ${config.PORT}</p>
+  `);
+});
+
+app.listen(config.PORT, () => {
+    console.log(`✅ ${config.SERVICE_NAME} is running on port ${config.PORT}`);
+});

docker-modules/managing-multiple-docker-containers-same-image-different-configs/config/analytics-config.json

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+{
+    "SERVICE_NAME": "analytics-processor",
+    "ENVIRONMENT": "staging",
+    "LOG_LEVEL": "debug",
+    "PORT": 3005
+}

docker-modules/managing-multiple-docker-containers-same-image-different-configs/config/notification-config.json

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+{
+    "SERVICE_NAME": "notification-worker",
+    "ENVIRONMENT": "production",
+    "LOG_LEVEL": "info",
+    "PORT": 3006
+}

docker-modules/managing-multiple-docker-containers-same-image-different-configs/docker-compose.env.yml

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+services:
+  audit_logger:
+    build:
+      context: .
+      dockerfile: Dockerfile
+    container_name: audit_logger
+    environment:
+      - SERVICE_NAME=audit-logger
+      - ENVIRONMENT=qa
+      - LOG_LEVEL=warn
+      - PORT=3003
+    ports:
+      - "3003:3003"
+
+  report_engine:
+    build:
+      context: .
+      dockerfile: Dockerfile
+    container_name: report_engine
+    environment:
+      - SERVICE_NAME=report-engine
+      - ENVIRONMENT=dev
+      - LOG_LEVEL=error
+      - PORT=3004
+    ports:
+      - "3004:3004"

docker-modules/managing-multiple-docker-containers-same-image-different-configs/docker-compose.file.yml

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+services:
+  analytics_processor:
+    build:
+      context: .
+      dockerfile: Dockerfile
+    container_name: analytics_processor
+    environment:
+      - CONFIG_PATH=/app/config.json
+    volumes:
+      - ./config/analytics-config.json:/app/config.json
+    ports:
+      - "3005:3005"
+
+  notification_worker:
+    build:
+      context: .
+      dockerfile: Dockerfile
+    container_name: notification_worker
+    environment:
+      - CONFIG_PATH=/app/config.json
+    volumes:
+      - ./config/notification-config.json:/app/config.json
+    ports:
+      - "3006:3006"