Docker+Nginx环境下Laravel API无法访问（502错误）求助

我正在开发一个以Laravel为后端API、NextJS为独立前端的应用，采用Docker与Nginx部署。目前Nginx配置完成后可正常访问前端UI，但请求Laravel API端点时出现502 Bad Gateway错误。以下是相关配置及错误信息：

Docker-compose配置 #

services:

  ###### FRONTEND SERVICES

  ## Node容器（运行NextJS前端项目）
  findra-node:
    build:
      context: ./docker/node
    container_name: findra-node
    restart: unless-stopped
    volumes:
      - type: bind
        source: ./federer
        target: /var/www/finaldraw/federer
    working_dir: /var/www/finaldraw/federer
    command: ["npm", "run", "dev"]
    healthcheck:
      test: ["CMD", "curl", "-f", "finaldraw.local:3000"]
      interval: 15s
      timeout: 5s
      retries: 150
    networks:
      - frontend

  ###### BACKEND SERVICES

  ## Nginx容器
  findra-nginx:
    container_name: findra-nginx
    build:
      context: ./docker/nginx
      dockerfile: Dockerfile
    restart: unless-stopped
    depends_on:
      findra-php:
        condition: service_healthy
      findra-node:
        condition: service_healthy
    ports:
      - protocol: tcp
        published: ${NGINX_PORT}
        target: 80
    healthcheck:
      test: ["CMD", "curl", "-k", "-f", "finaldraw.local:80"]
      interval: 15s
      timeout: 5s
      retries: 150
    networks:
      - frontend
      - backend

  ## PHP容器（运行Laravel后端）
  findra-php:
    container_name: findra-php
    build:
      context: ./docker/php
      args:
        USER_ID: ${USER_ID:-0}
        GROUP_ID: ${GROUP_ID:-0}  
    user: www-data:www-data
    restart: unless-stopped
    volumes:
      - type: bind
        source: ./nadal
        target: /var/www/finaldraw/nadal
    working_dir: /var/www/finaldraw/nadal
    healthcheck:
      test: ["CMD", "php-fpm-healthcheck"]
      interval: 15s
      timeout: 5s
      retries: 150
    networks:
      - backend

Nginx配置 #

upstream federer {
  server findra-node:3000;
}

upstream nadal {
  server findra-php:9000;
}

server {
    listen 80;
    listen [::]:80;

    server_name mysite.local;

    charset utf-8;

    location / {    
        proxy_pass http://federer/; 
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;           
    } 

    location /api/ {
        proxy_pass http://nadal/;
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    }
}

PHP Dockerfile已暴露9000端口，Node Dockerfile已暴露3000端口。访问前端http://mysite.local/正常，但请求API http://finaldraw.local/api/时返回：

<html>

<head>
    <title>502 Bad Gateway</title>
</head>

<body>
    <center>
        <h1>502 Bad Gateway</h1>
    </center>
    <hr>
    <center>nginx/1.27.0</center>
</body>

</html>

1. 修正Nginx对PHP-FPM的协议适配 #

PHP-FPM使用FastCGI协议，而非HTTP，不能用proxy_pass转发请求。修改Nginx的/api/配置块为FastCGI模式：

location /api/ {
    root /var/www/finaldraw/nadal/public;
    try_files $uri $uri/ /index.php$is_args$args;

    fastcgi_pass http://nadal;
    fastcgi_index index.php;
    fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
    include fastcgi_params;

    proxy_set_header Host $host;
    proxy_set_header X-Real-IP $remote_addr;
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
}

2. 统一域名访问 #

前端使用mysite.local，API请求用finaldraw.local，需确保两个域名都指向Nginx容器的IP（修改本地/etc/hosts或DNS记录），或统一使用同一个域名避免跨域与解析问题。

3. 验证容器网络连通性 #

进入Nginx容器，测试能否连接到PHP-FPM容器：

# 测试ping连通性
docker exec -it findra-nginx ping findra-php
# 测试端口连通性
docker exec -it findra-nginx telnet findra-php 9000

若无法连通，检查Docker网络配置：执行docker network inspect backend确认findra-nginx和findra-php均加入backend网络。

4. 确认PHP-FPM监听配置 #

进入PHP容器，检查PHP-FPM是否正常监听9000端口：

docker exec -it findra-php netstat -tulpn | grep 9000

若未监听，修改PHP-FPM配置文件（通常在/usr/local/etc/php-fpm.d/www.conf），确保listen = 0.0.0.0:9000（允许容器外部访问），而非listen = 127.0.0.1:9000（仅本地访问）。

5. 修复Laravel目录权限 #

确保PHP容器内的Laravel目录权限正确，www-data用户拥有读写权限：

docker exec -it findra-php chown -R www-data:www-data /var/www/finaldraw/nadal
docker exec -it findra-php chmod -R 755 /var/www/finaldraw/nadal/storage /var/www/finaldraw/nadal/bootstrap/cache

内容的提问来源于stack exchange，提问作者Juan Pablo B