Next.js + Prisma 无法连接Docker PostgreSQL问题求助

我想要将Next.js全栈应用Docker化，但出现错误提示：Please make sure your database server is running at db:5433。我尝试修改数据库名称为localhost、db、pgdb等，但均无效。

容器启动后，我可以通过pgAdmin使用localhost作为数据库名称、5433作为端口连接PostgreSQL，但Next.js应用无法连接。

我的Dockerfile： #

FROM node:18-alpine AS base

# Install dependencies only when needed
FROM base AS deps
# Check https://github.com/nodejs/docker-node/tree/b4117f9333da4138b03a546ec926ef50a31506c3#nodealpine to understand why libc6-compat might be needed.
RUN apk add --no-cache libc6-compat
WORKDIR /app

# Install dependencies based on the preferred package manager
COPY package.json yarn.lock* package-lock.json* pnpm-lock.yaml* ./
RUN \
    if [ -f yarn.lock ]; then yarn --frozen-lockfile; \
    elif [ -f package-lock.json ]; then npm ci; \
    elif [ -f pnpm-lock.yaml ]; then corepack enable pnpm && pnpm i --frozen-lockfile; \
    else echo "Lockfile not found." && exit 1; \
    fi

# Rebuild the source code only when needed
FROM base AS builder
WORKDIR /app
COPY --from=deps /app/node_modules ./node_modules
COPY . .

# Next.js collects completely anonymous telemetry data about general usage.
# Learn more here: https://nextjs.org/telemetry
# Uncomment the following line in case you want to disable telemetry during the build.
# ENV NEXT_TELEMETRY_DISABLED 1

RUN \
    if [ -f yarn.lock ]; then yarn run build; \
    elif [ -f package-lock.json ]; then npm run build; \
    elif [ -f pnpm-lock.yaml ]; then corepack enable pnpm && pnpm run build; \
    else echo "Lockfile not found." && exit 1; \
    fi

# Production image, copy all the files and run next
FROM base AS runner
WORKDIR /app

ENV NODE_ENV production
# Uncomment the following line in case you want to disable telemetry during runtime.
# ENV NEXT_TELEMETRY_DISABLED 1

RUN addgroup --system --gid 1001 nodejs
RUN adduser --system --uid 1001 nextjs

COPY --from=builder /app/public ./public

# Set the correct permission for prerender cache
RUN mkdir .next
RUN chown nextjs:nodejs .next

# Automatically leverage output traces to reduce image size
# https://nextjs.org/docs/advanced-features/output-file-tracing
COPY --from=builder --chown=nextjs:nodejs /app/.next/standalone ./
COPY --from=builder --chown=nextjs:nodejs /app/.next/static ./.next/static

USER nextjs

EXPOSE 3000

ENV PORT 3000
# set hostname to localhost
ENV HOSTNAME "0.0.0.0"

# server.js is created by next build from the standalone output
# https://nextjs.org/docs/pages/api-reference/next-config-js/output
CMD ["node", "server.js"]

我的docker-compose.yml配置： #

services:
  app:
    container_name: frontend
    build:
      context: .
      dockerfile: Dockerfile
    ports:
      - "3000:3000"
    depends_on:
      db:
        condition: service_healthy
    restart: always

  db:
    container_name: pgdb
    image: postgres:latest
    restart: always
    environment:
      POSTGRES_USER: postgres
      POSTGRES_PASSWORD: postgres
      POSTGRES_DB: docker
    ports:
      - "5433:5432"
    healthcheck:
      test: ["CMD-SHELL", "pg_isready -U postgres"]
      interval: 5s
      timeout: 5s
      retries: 5

问题核心是容器间通信的端口与主机名配置错误，按以下步骤修复：

• 修正数据库连接端口
  Docker Compose中，db容器内部的PostgreSQL默认运行在5432端口，宿主机的5433端口只是给外部工具（如pgAdmin）用的。容器间通信必须使用容器内部端口，所以Next.js应用的数据库连接配置里，端口要设为5432，而非5433。

• 确认主机名使用db
  Docker Compose会自动为同一网络下的容器创建DNS解析，db是docker-compose.yml里定义的服务名，是容器间通信的标准主机名，不要用localhost或容器名pgdb。

• 通过环境变量传递连接配置
  建议在docker-compose.yml的app服务中添加环境变量，避免硬编码连接字符串：

  app:
    # 保留原有配置
    environment:
      - DATABASE_URL=postgresql://postgres:postgres@db:5432/docker
  

  然后在Next.js项目中读取这个环境变量建立数据库连接。

• 验证容器网络连通性
  如果仍有问题，可进入frontend容器测试与db的连通性：

  # 测试DNS解析
  docker exec -it frontend ping db
  # 测试端口连通
  docker exec -it frontend apk add telnet && telnet db 5432
  

  若能连通，说明网络正常，问题出在应用的连接配置上。

内容的提问来源于stack exchange，提问作者ReactLover