【Bug Log】Error caused by outdated version of Node.js in pm2 process.

Dec 21, 2023#bug日志 #nomland #nunti #pm2 #nodejs #op107

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In December 17, 2023, while developing a Discord bot, the user encountered an error "Error: Cannot find module 'readline/promises'" on the server side, but not locally. The issue was suspected to be related to the version of Node.js on the server. After checking and finding that the server's Node.js version was v16.19.1, it was suspected that the error was caused by a low version of Node.js. The user upgraded Node.js to v21.4.0 using nvm, but the bot error still persisted. The user tried to minimize the error by running the code in the Node.js REPL, but no error occurred. They also downloaded the elephant SDK separately, installed the dependencies using npm, and ran the example.ts file, which worked fine. The user then realized that the bot had been restarted using pm2, which might be using the old version of Node.js. To test this hypothesis, they checked the pm2 version and found that it was indeed using Node.js version 16.19.1. They upgraded pm2 and restarted the pm2 process. After checking again, they confirmed that the Node.js version had been successfully upgraded. They tested the bot again and it worked successfully.

Date: 2023.12.17

Issue: When developing a discord bot, encountered the error "Error: Cannot find module 'readline/promises'" on the server side. However, there were no errors locally.

Solution Process:

"readline/promises" is a library used by the bot's dependency, elephant-sdk. According to this search result, it is initially believed that it may be related to the version of nodejs.

Checked the server's nodejs version, which is v16.19.1, suspecting that the error is caused by a low version of nodejs on the server.

root@nunti-bot:~# node -v
v16.19.1

Upgraded nodejs to v21.4.0 using nvm. However, the bot's error still persists.
Attempted to minimize the error. Ran the code in the Node.js REPL (Read-Eval-Print Loop):
const readline = require('readline/promises');
No error occurred.
Downloaded the elephant sdk separately, installed dependencies using npm (the same package manager as the bot), and ran the example.ts provided in the repository, which ran successfully.
At this point, there was no clear direction. After putting it aside for a while, I suddenly realized before going to bed that the bot had been restarted during testing using pm2. It is likely that pm2 is still using the old version of nodejs. To verify this hypothesis, I used pm2 show 'app-name' to check and indeed found a line in the returned result: │ node.js version │ 16.19.1.
According to this search result, upgraded pm2 and restarted the pm2 process:
```
pm2 update
pm2 restart app --update-env
```
Then checked again using pm2 show, and this time the nodejs version was successfully upgraded. Tested the bot again and it worked.