Identify Errors

Before you start

• Understand the code you are hosting.
• Use a text editor or IDE (recommended) to update your files.

Add error logging

Server logs show why an application stops or behaves unexpectedly. Add logging to your main entry file before your application starts.

Node.js exceptions and promise rejections

// Logs synchronous runtime errors that reach the event loop.
process.on("uncaughtException", (error, origin) => {
  console.error(`[CRITICAL ERROR] Uncaught Exception at: ${origin}`);
  console.error(error.stack || error);
});

// Logs promise rejections that have no error handler.
process.on("unhandledRejection", (reason, promise) => {
  console.error("[CRITICAL ERROR] Unhandled Promise Rejection:", promise);
  console.error("Reason:", reason?.stack || reason);
});

Discord.js REST event logging

Use REST events to log specific response codes and take action based on them.

client.rest.on(RESTEvents.Response, (Req, Resp) => {
    if (!(Resp.status === 429)) return;
    console.log('[429] Rate limited!')
});

Identify the cause

1. Restart the server and reproduce the problem.
2. Review the first error in the console output.
3. Trace the stack back to your code or configuration.

The final error can be a symptom. Earlier log entries often show the root cause.