使用env_file配置PostgreSQL环境变量时Docker-Compose报错

错误信息 #

执行docker-compose build时出现以下错误：

time="2023-10-16T16:43:46-04:00" level=warning msg="The \"PGUSER\" variable is not set. Defaulting to a blank string."
time="2023-10-16T16:43:46-04:00" level=warning msg="The \"PGPASSWORD\" variable is not set. Defaulting to a blank string."
time="2023-10-16T16:43:46-04:00" level=warning msg="The \"PGDATABASE\" variable is not set. Defaulting to a blank string."
time="2023-10-16T16:43:46-04:00" level=warning msg="The \"PGPORT\" variable is not set. Defaulting to a blank string."
time="2023-10-16T16:43:46-04:00" level=warning msg="The \"PGPORT\" variable is not set. Defaulting to a blank string."
1 error(s) decoding:

* error decoding 'ports': No port specified: :<empty>

现有配置文件 #

docker-compose.yml #

version: "3.11"
services:
 app:
  container_name: app_container
  build: .
  volumes:
   - .:/django
  ports:
   - 8000:8000
  image: app:django
  command: python manage.py runserver 0.0.0.0:8000
  depends_on:
   - db
 db:
  container_name: postgres_container
  env_file:
   - .env.prod
  image: postgres
  restart: always
  environment:
   POSTGRES_USER: ${PGUSER}
   POSTGRES_PASSWORD: ${PGPASSWORD}
   POSTGRES_DB: ${PGDATABASE}
  ports:
   - "${PGPORT}:${PGPORT}"
 pgadmin:
  container_name: pgadmin4_container
  image: dpage/pgadmin4
  restart: always
  environment:
   PGADMIN_DEFAULT_EMAIL: admin@admin.com
   PGADMIN_DEFAULT_PASSWORD: Password12345
  ports:
   - "5050:80"

.env.prod #

PGHOST="127.0.0.1"
PGUSER="postgres"
PGPORT=5432
PGDATABASE="dev_db"
PGPASSWORD="postgres"

文件目录结构：

问题原因 #

1. 变量读取范围错误：docker-compose.yml中用${PGUSER}、${PGPORT}这类语法引用的变量，是从docker-compose命令运行时的主机环境读取的，而非db服务配置的env_file。env_file仅负责将变量注入容器内部环境，无法被docker-compose本身用来解析配置文件中的变量占位符。
2. 环境变量格式错误：.env.prod中给变量值添加了引号，会导致变量值包含引号字符，引发解析异常。

解决方案 #

方案1：全局配置env_file让docker-compose读取变量 #

在docker-compose.yml顶部添加全局env_file配置，让docker-compose直接读取.env.prod中的变量来解析占位符：

version: "3.11"
# 全局配置，让docker-compose读取该文件的变量
env_file:
  - .env.prod
services:
 app:
  container_name: app_container
  build: .
  volumes:
   - .:/django
  ports:
   - 8000:8000
  image: app:django
  command: python manage.py runserver 0.0.0.0:8000
  depends_on:
   - db
 db:
  container_name: postgres_container
  env_file:
   - .env.prod
  image: postgres
  restart: always
  environment:
   POSTGRES_USER: ${PGUSER}
   POSTGRES_PASSWORD: ${PGPASSWORD}
   POSTGRES_DB: ${PGDATABASE}
  ports:
   - "${PGPORT}:${PGPORT}"
 pgadmin:
  container_name: pgadmin4_container
  image: dpage/pgadmin4
  restart: always
  environment:
   PGADMIN_DEFAULT_EMAIL: admin@admin.com
   PGADMIN_DEFAULT_PASSWORD: Password12345
  ports:
   - "5050:80"

方案2：简化端口配置（推荐） #

PostgreSQL默认端口为5432，无需动态配置，直接写死端口映射，同时保留db服务的env_file给容器内部注入变量：

# 修改db服务的ports部分
db:
  container_name: postgres_container
  env_file:
   - .env.prod
  image: postgres
  restart: always
  environment:
   POSTGRES_USER: ${PGUSER}
   POSTGRES_PASSWORD: ${PGPASSWORD}
   POSTGRES_DB: ${PGDATABASE}
  ports:
   - "5432:5432"

通用修正：修复.env.prod格式 #

去掉变量值的引号，确保环境变量值正确：

PGHOST=127.0.0.1
PGUSER=postgres
PGPORT=5432
PGDATABASE=dev_db
PGPASSWORD=postgres

验证 #

修改完成后，重新执行docker-compose build和docker-compose up，即可正常启动容器。

内容的提问来源于stack exchange，提问作者code writer 3000