Fix Insufficient Logging & Monitoring in ElysiaJS

Silent failures are an attacker's best friend. In the Bun/Elysia ecosystem, performance often overshadows visibility. If you aren't implementing structured logging and real-time monitoring, you are effectively blind to credential stuffing, forced browsing, and RCE attempts. Insufficient logging allows threats to persist undetected for months. We need to move from 'silent' to 'auditable' by leveraging structured loggers and global error hooks.

The Vulnerable Pattern

import { Elysia } from 'elysia';
const app = new Elysia()
.post(‘/api/v1/login’, ({ body }) => {
// VULNERABILITY: No logging of authentication attempts.
// If an attacker brutes this endpoint, there is no audit trail.
return { status: ‘ok’ };
})
.get(‘/api/admin/config’, () => {
// VULNERABILITY: Access to sensitive endpoints is not logged.
return { config: ‘secret’ };
})
.listen(3000);

The Secure Implementation

To fix insufficient logging in Elysia, you must implement three pillars: 1. Structured Logging: Use middleware like @bogeychan/elysia-logger to output JSON logs that can be ingested by an ELK stack or SIEM. 2. Error Correlation: Utilize the .onError() lifecycle hook to capture unhandled exceptions and 4xx/5xx status codes, which often indicate scanning or exploitation attempts. 3. Contextual Data: Always log the request method, URI, source IP, and a unique Request-ID to correlate logs across distributed services. Ensure sensitive data like passwords or session tokens are redacted using the 'redact' configuration to prevent log-based data leakage.

import { Elysia } from 'elysia';
import { logger } from '@bogeychan/elysia-logger';
const app = new Elysia()
.use(
logger({
level: ‘info’,
// Ensure we don’t log sensitive PII or credentials
redact: [‘body.password’, ‘headers.authorization’]
})
)
.onError(({ code, error, request, set }) => {
// Centralized security monitoring for 4xx/5xx errors
console.error(JSON.stringify({
timestamp: new Date().toISOString(),
method: request.method,
path: request.url,
error: error.message,
code: code,
ip: request.headers.get(‘x-forwarded-for’)
}));
})
.post(‘/api/v1/login’, ({ body, request }) => {
// Log security-critical events manually if necessary
return { status: ‘ok’ };
})
.listen(3000);