使用Go与Docker部署时无法连接PostgreSQL数据库的问题

尝试构建包含Go模块和PostgreSQL的Docker容器，但Go模块无法连接到PostgreSQL，相关配置与报错如下：

.env 文件配置 #

HOST=0.0.0.0
SERVER_PORT=3000
DB_USER=postgres
DB_PASSWORD=12345
DB_NAME=unity
DB_PORT=5432

docker-compose.yaml 配置 #

version: "3.8"
services:
  scraper:
    build: .
    restart: unless-stopped
    depends_on:
      postgres:
        condition: service_healthy
    env_file:
      - .env
    ports:
      - "${SERVER_PORT}:${SERVER_PORT}"
    volumes:
      - .:/usr/src/app
    command: go run cmd/main.go
  air:
    image: cosmtrek/air:latest
    working_dir: /usr/src/app
    ports:
      - 3001:3001
    environment:
      - ENV_A=${ENV_A}
      - ENV_B=${ENV_B}
      - ENV_C=${ENV_C}
    volumes:
      - .:/usr/src/app
  postgres:
    image: postgres:latest
    restart: unless-stopped
    environment:
      - POSTGRES_USER=${DB_USER}
      - POSTGRES_PASSWORD=${DB_PASSWORD}
      - POSTGRES_DB=${DB_NAME}
    ports:
      - "${DB_PORT}:${DB_PORT}"
    volumes:
      - postgres_db:/var/lib/postgresql/data
    healthcheck:
      test: ["CMD-SHELL", "pg_isready -d ${DB_NAME} -U ${DB_USER}"]
      interval: 3s
      timeout: 3s
      retries: 5
volumes:
  postgres_db:

database.go 连接代码 #

package databases

import (
    "fmt"
    "log"
    "os"

    "github.com/DespairServices/despair-services-scrapper/internal/models"
    "gorm.io/driver/postgres"
    "gorm.io/gorm"
    "gorm.io/gorm/logger"
)

var db *gorm.DB
var dsn string = fmt.Sprintf(
    "host=%s user=%s password=%s dbname=%s port=%s sslmode=disable TimeZone=Asia/Shanghai",
    os.Getenv("HOST"),
    os.Getenv("DB_USER"),
    os.Getenv("DB_PASSWORD"),
    os.Getenv("DB_NAME"),
    os.Getenv("DB_PORT"),
)

func Connect() {
    db, err := gorm.Open(postgres.Open(dsn), &gorm.Config{
        Logger: logger.Default.LogMode(logger.Info),
    })

    if err != nil {
        log.Fatal("Failed to connect to database. \n", err)
        os.Exit(2)
    }

    log.Println("Database Connected!")
    log.Println("Running Migrations...")
    db.AutoMigrate(&models.Asset{})
    log.Println("Migrations Done!")
}

PostgreSQL就绪日志 #

2024-04-05 21:03:27 2024-04-06 01:03:27.074 UTC [1] LOG:  listening on IPv4 address "0.0.0.0", port 5432
2024-04-05 21:03:27 2024-04-06 01:03:27.074 UTC [1] LOG:  listening on IPv6 address "::", port 5432
2024-04-05 21:03:27 2024-04-06 01:03:27.083 UTC [1] LOG:  listening on Unix socket "/var/run/postgresql/.s.PGSQL.5432"
2024-04-05 21:03:27 2024-04-06 01:03:27.093 UTC [29] LOG:  database system was shut down at 2024-04-06 01:00:11 UTC
2024-04-05 21:03:27 2024-04-06 01:03:27.103 UTC [1] LOG:  database system is ready to accept connections

Go模块连接报错 #

2024-04-05 21:04:48 2024/04/06 01:04:48 /usr/src/app/internal/databases/database.go:26
2024-04-05 21:04:48 [error] failed to initialize database, got error failed to connect to `host=0.0.0.0 user=postgres database=unity`: dial error (dial tcp 0.0.0.0:5432: connect: connection refused)

核心问题是Docker容器间的网络寻址方式错误：在Docker Compose创建的默认网络中，容器需要通过服务名称互相访问，而不是0.0.0.0。0.0.0.0表示容器自身监听所有接口，但不是其他容器用来连接的地址。

具体修改步骤： #

• 修改.env文件中的HOST值：
  将.env里的HOST=0.0.0.0改为HOST=postgres（对应docker-compose中PostgreSQL服务的名称）：

  HOST=postgres
  SERVER_PORT=3000
  DB_USER=postgres
  DB_PASSWORD=12345
  DB_NAME=unity
  DB_PORT=5432
  

• 或者在docker-compose中覆盖环境变量：
  如果不想修改.env文件，可以在scraper服务的environment中添加HOST=postgres，覆盖.env的值：

  scraper:
    build: .
    restart: unless-stopped
    depends_on:
      postgres:
        condition: service_healthy
    env_file:
      - .env
    environment:
      - HOST=postgres  # 新增这一行，覆盖.env中的HOST
    ports:
      - "${SERVER_PORT}:${SERVER_PORT}"
    volumes:
      - .:/usr/src/app
    command: go run cmd/main.go
  

• 验证修改效果：
  重新启动容器：

  docker-compose down && docker-compose up --build
  

  此时Go模块会通过服务名postgres访问PostgreSQL容器，Docker的DNS服务会自动解析到对应的容器IP，连接即可成功。

内容的提问来源于stack exchange，提问作者Dennis Solomon