React+Express+Mongo应用部署至DigitalOcean Ubuntu 20.04服务器后端故障排查求助

各位好，我现在在把一套React+Express+Mongo的遗留系统部署到DigitalOcean的Ubuntu 20.04服务器上时，后端出现了关键故障，折腾了好久都没解决，希望能得到大家的帮助🙏

部署环境说明 #

• 服务器：DigitalOcean Ubuntu 20.04 x64，默认配置，未开启防火墙
• 依赖版本：Node.js 14.18.3、MongoDB 4.4（都是项目要求的固定版本，不能升级，因为是遗留系统）
• 运行状态：React前端（3000端口）用pm2托管，能正常显示登录页，功能正常；Express后端（3333端口）同样用pm2托管，但出现异常

具体问题现象 #

1. 接口请求异常
   前端调用后端接口失败，为了排除前后端交互的问题，我用Postman直接请求后端的登录接口，依然报错。请求示例：

curl --location --request POST 'http://<ip地址>:3333/auth/login' \
--header 'x-company-id: 1' \
--header 'Content-Type: application/json' \
--data-raw '{
"email": "user@email.com",
"password": "123"
}'

遇到的错误包括：ERR_TOO_MANY_REDIRECTS、Error: connect ECONNREFUSED

2. 端口相关的奇怪表现

• 访问http://<ip地址>:3333/ping能正常返回pong，说明3333端口没有被阻塞
• 直接访问http://<ip地址>:3333/时，返回内容是Found. Redirecting to /，出现无意义的重定向

3. pm2日志中的错误
   后端用pm2运行时，日志抛出了内存相关的错误：

6|backend  | npm ERR! code ELIFECYCLE
6|backend  | npm ERR! errno 137
6|backend  | npm ERR! node-api-dpo@1.0.0 start: `babel-node -- index.js`
6|backend  | npm ERR! Exit status 137
6|backend  | npm ERR!
6|backend  | npm ERR! Failed at the node-api-dpo@1.0.0 start script.
6|backend  | npm ERR! This is probably not a problem with npm. There is likely additional logging output above.
6|backend  |
6|backend  | npm ERR! A complete log of this run can be found in:
6|backend  | npm ERR!     /root/.npm/_logs/2023-12-09T15_18_09_271Z-debug.log
6|backend  | (node:49419) NOTE: We are formalizing our plans to enter AWS SDK for JavaScript (v2) into maintenance mode in 2023.
6|backend  |
6|backend  | (Use `node --trace-warnings ...` to show where the warning was created)

注：AWS SDK的提示是无关的，因为项目暂时还没升级到v3

4. 直接启动后端的错误
   如果不用pm2，直接在服务器上运行npm start，会抛出解密相关的错误：

events.js:377
throw er; // Unhandled 'error' event
^

Error: Error during decryption (probably incorrect key). Original error: Error: error:04099079:rsa routines:RSA_padding_check_PKCS1_OAEP_mgf1:oaep decoding error
at NodeRSA.module.exports.NodeRSA.$$decryptKey (/root/compassDPO/climby_api_DPO/service/node_modules/node-rsa/src/NodeRSA.js:301:19)
at NodeRSA.module.exports.NodeRSA.decrypt (/root/compassDPO/climby_api_DPO/service/node_modules/node-rsa/src/NodeRSA.js:249:21)
at Utils.decrypt (/root/compassDPO/climby_api_DPO/service/src/utils/utils.js:454:24)
at /root/compassDPO/climby_api_DPO/service/src/oauth/services.js:48:26
at model.Query.<anonymous> (/root/compassDPO/climby_api_DPO/service/node_modules/mongoose/lib/model.js:3932:16)
at /root/compassDPO/climby_api_DPO/service/node_modules/kareem/index.js:273:21
at /root/compassDPO/climby_api_DPO/service/node_modules/kareem/index.js:131:16
at processTicksAndRejections (internal/process/task_queues.js:77:11)
Emitted 'error' event on Function instance at:
at model.Query.<anonymous> (/root/compassDPO/climby_api_DPO/service/node_modules/mongoose/lib/model.js:3934:13)
at /root/compassDPO/climby_api_DPO/service/node_modules/kareem/index.js:273:21
at /root/compassDPO/climby_api_DPO/service/node_modules/kareem/index.js:131:16
at processTicksAndRejections (internal/process/task_queues.js:77:11)
npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! node-api-dpo@1.0.0 babel-node: `babel-node --presets=latest "index.js"`
npm ERR! Exit status 1
npm ERR!
npm ERR! Failed at the node-api-dpo@1.0.0 babel-node script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.
npm ERR! A complete log of this run can be found in:
npm ERR!     /root/.npm/_logs/2023-12-10T12_30_45_631Z-debug.log
[nodemon] app crashed - waiting for file changes before starting...

已完成的排查动作 #

• 本地开发环境运行完全正常，没有任何问题
• 重新创建了两次全新的DigitalOcean服务器，从头部署，问题依然存在
• 确认3333端口没有被阻塞：/ping接口正常响应
• 检查了MongoDB连接，确认服务正常运行，能正常读写数据
• 检查了项目中的.pem密钥文件，和本地的一致，路径配置也正确

现在我实在想不到还有什么地方可以排查了，有没有朋友遇到过类似的问题？或者有什么排查思路可以推荐？如果需要我做其他测试或者提供更多日志/配置信息，随时告诉我，非常感谢大家的帮助！

备注：内容来源于stack exchange，提问作者Marcos Lemos