“ ConnectionError：连接ECONNREFUSED”，无法使用Docker Compose连接Node.js应用程序和Elasticsearch数据库

Question

当我在Docker的同一网桥网络上运行时，我正在尝试使我的Node.js应用程序与我的Elasticsearch数据库对话。我使用docker-compose.yml文件进行配置。这是相关的位和我收到的错误消息。

docker-compose.yml

version: '3'

services:
  express-app:
    build: /path/to/app
    container_name: my_app
    depends_on:
      - 'elasticsearch'
    environment:
     - NODE_ENV=local
     - ES_HOST=elasticsearch
     - PORT=3000
    ports:
      - 3000:3000
    networks:
      - backend

  elasticsearch:
    image: docker.elastic.co/elasticsearch/elasticsearch:7.6.0
    container_name: es-master
    environment:
      - discovery.type=single-node
      - bootstrap.memory_lock=true
      - "ES_JAVA_OPTS=-Xms512m -Xmx512m"
    volumes:
      - esdata:/usr/share/elasticsearch/data
    ports:
      - 9200:9200
      - 9300:9300
    networks:
      - backend

volumes:
  esdata:
    driver: local

networks:
  backend:

我希望服务（express-app和elasticsearch都可以在创建的Docker桥接网络“ my_app_backend”上以其服务名称被发现。官方Docker documentation指出“服务可以在主机名上访问。”我的意图是在地址“ {http://elasticsearch:9200”处访问服务elasticsearch。

Node.js应用程序内的数据库连接定义（server / db / index.js）

const { Client } = require('@elastic/elasticsearch');
const hostname = process.env.ES_HOST || 'localhost';
const client = new Client({
  node: `http://${hostname}:9200`,
  log: 'error'
});

async function checkConnection () {
  let isConnected = false;
  console.log('Connecting to host', hostname);
  try {
    const health = await client.cluster.health({});
    console.log(health);
    isConnected = true;
  } catch (err) {
    console.log('process.env.ES_HOST', process.env.ES_HOST);
    console.log('Connection Failed\n', err);
  }
}

checkConnection();

module.exports.client = client;

以下消息显示Node.js应用尝试通过process.env.ES_HOST变量'elasticsearch'（在docker-compose.yml文件中定义）连接到Elasticsearch的结果，并在容器运行时执行。错误消息显示了我放入的两个控制台日志，以检查变量的值是否正确。

ECONNREFUSED之后显示的IP地址是Docker引擎替换为“ elasticsearch”的地址。当我运行输出容器的网络地址的docker network inspect my_app_backend时，也会发现这一点。

... (redacted)
"MacAddress": "02:42:ac:14:00:03",
                "IPv4Address": "172.20.0.3/16",
                "IPv6Address": ""

错误消息

> NODE_ENV=production node ./server/index.js

Connecting to host elasticsearch
Server listening on port 3000!
process.env.ES_HOST elasticsearch
Connection Failed
 ConnectionError: connect ECONNREFUSED 172.20.0.3:9200
    at onResponse (/src/app/node_modules/@elastic/elasticsearch/lib/Transport.js:214:13)
    at ClientRequest.<anonymous> (/src/app/node_modules/@elastic/elasticsearch/lib/Connection.js:98:9)
    at ClientRequest.emit (events.js:311:20)
    at Socket.socketErrorListener (_http_client.js:426:9)
    at Socket.emit (events.js:311:20)
    at emitErrorNT (internal/streams/destroy.js:92:8)
    at emitErrorAndCloseNT (internal/streams/destroy.js:60:3)
    at processTicksAndRejections (internal/process/task_queues.js:84:21) {
  name: 'ConnectionError',
  meta: {
    body: null,
    statusCode: null,
    headers: null,
    warnings: null,
    meta: {
      context: null,
      request: [Object],
      name: 'elasticsearch-js',
      connection: [Object],
      attempts: 3,
      aborted: false
    }
  }
}

此外，我想指出应用程序在启动时无法连接，但是当我通过docker exec -it express-app sh进入应用程序容器并编辑数据库连接代码并硬编码数据库的IP地址（172.20.0.3 ），然后重新启动节点应用程序，该应用程序已成功连接到数据库。

在通过docker-compose完全自动化的尝试中我做错了什么？这是Elasticsearch的怪癖还是我遗漏的很明显的东西？预先感谢您的帮助！

Answer 1

在express_app中使用container_name : es-master代替elasticsearch作为ES_HOST env变量

ES_HOST : es-master

Answer 2

我认为您应该链接elasticsearch容器

version: '3'

services:
  express-app:
    build: /path/to/app
    container_name: my_app
    restart: always
    depends_on:
      - 'elasticsearch'
    environment:
     - NODE_ENV=local
     - ES_HOST=elasticsearch
     - PORT=3000
    ports:
      - 3000:3000
    networks:
      - backend
    links: 
        - elasticsearch

  elasticsearch:
    image: docker.elastic.co/elasticsearch/elasticsearch:7.6.0
    container_name: es-master
    environment:
      - discovery.type=single-node
      - bootstrap.memory_lock=true
      - "ES_JAVA_OPTS=-Xms512m -Xmx512m"
    volumes:
      - esdata:/usr/share/elasticsearch/data
    ports:
      - 9200:9200
      - 9300:9300
    networks:
      - backend

volumes:
  esdata:
    driver: local

networks:
  backend: