Docker-Compose中FastAPI与PostgreSQL容器连接失败求助

• 仅PostgreSQL容器化、本地运行FastAPI时可正常连接，两者都容器化后，在Base.metadata.create_all(bind=engine)代码处出现连接拒绝错误
• 尝试修改main.py中的DATABASE_URL为postgresql://postgres:password@postgres:5433/fastapi_database后仍报错，不清楚配置文件管理方式

相关文件内容 #

Dockerfile #

FROM python:3.10-slim
WORKDIR /app
COPY . .
RUN pip install --upgrade pip
RUN pip install "fastapi[all]" sqlalchemy psycopg2-binary

docker-compose.yml #

version: '3.8'
services:
  ylab:
    container_name: ylab
    build:
      context: .
    entrypoint: >
      sh -c "uvicorn main:app --reload --host 0.0.0.0"
    ports:
      - "8000:8000"
  postgres:
    container_name: postgr
    image: postgres:15.1-alpine
    environment:
        POSTGRES_DB: "fastapi_database"
        POSTGRES_PASSWORD: "password"
    ports:
      - "5433:5432"

main.py #

import fastapi as _fastapi
import sqlalchemy as _sql
import sqlalchemy.ext.declarative as _declarative
import sqlalchemy.orm as _orm

DATABASE_URL = "postgresql://postgres:password@localhost:5433/fastapi_database"
engine = _sql.create_engine(DATABASE_URL)
SessionLocal = _orm.sessionmaker(autocommit=False, autoflush=False, bind=engine)
Base = _declarative.declarative_base()

class Menu(Base):
    __tablename__ = "menu"
    id = _sql.Column(_sql.Integer, primary_key=True, index=True)
    title = _sql.Column(_sql.String, index=True)
    description = _sql.Column(_sql.String, index=True)

app = _fastapi.FastAPI()

# Create table 'menu'
Base.metadata.create_all(bind=engine)

报错信息 #

初始配置报错 #

sqlalchemy.exc.OperationalError: (psycopg2.OperationalError) connection to server at "localhost" (127.0.0.1), port 5433 failed: Connection refused
ylab        |   Is the server running on that host and accepting TCP/IP connections?
ylab        | connection to server at "localhost" (::1), port 5433 failed: Cannot assign requested address
ylab        |   Is the server running on that host and accepting TCP/IP connections?

修改DATABASE_URL后报错 #

sqlalchemy.exc.OperationalError: (psycopg2.OperationalError) connection to server at "postgres" (172.23.0.2), port 5433 failed: Connection refused
ylab        |   Is the server running on that host and accepting TCP/IP connections?

解决方案 #

1. 修正数据库连接端口 #

容器内部PostgreSQL使用默认端口5432，而非映射到宿主机的5433。修改main.py中的DATABASE_URL：

DATABASE_URL = "postgresql://postgres:password@postgres:5432/fastapi_database"

2. 配置容器依赖与网络 #

在docker-compose.yml中添加服务依赖，确保PostgreSQL容器先启动；同时显式配置网络（默认网络已互通，显式配置更清晰）：

version: '3.8'
services:
  ylab:
    container_name: ylab
    build:
      context: .
    entrypoint: >
      sh -c "uvicorn main:app --reload --host 0.0.0.0"
    ports:
      - "8000:8000"
    depends_on:
      - postgres
    networks:
      - app-network
  postgres:
    container_name: postgr
    image: postgres:15.1-alpine
    environment:
        POSTGRES_DB: "fastapi_database"
        POSTGRES_PASSWORD: "password"
        POSTGRES_USER: "postgres"
    ports:
      - "5433:5432"
    networks:
      - app-network
networks:
  app-network:
    driver: bridge

3. 延迟数据库初始化 #

将表创建逻辑放到FastAPI启动事件中，避免PostgreSQL容器未就绪时执行初始化：
修改main.py：

# 保留原有代码...
app = _fastapi.FastAPI()

@app.on_event("startup")
def startup_event():
    Base.metadata.create_all(bind=engine)

4. 环境变量管理（推荐） #

将数据库配置从代码中剥离，通过环境变量传递，避免硬编码：

• 修改docker-compose.yml中ylab服务：

  environment:
    - DATABASE_URL=postgresql://postgres:password@postgres:5432/fastapi_database
  

• 修改main.py读取环境变量：

  import os
  DATABASE_URL = os.getenv("DATABASE_URL", "postgresql://postgres:password@postgres:5432/fastapi_database")
  

内容的提问来源于stack exchange，提问作者Evgeny Romensky