PDF Viewer Worker Failure & File Load Error

[kusumavishu]

🐞 Issue: PDF Viewer Worker Failure & File Load Error

📌 Summary

We are encountering issues while rendering PDFs in the application. The PDF viewer is failing to load properly due to a worker configuration problem, and in some cases, the PDF file itself is not accessible.

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⚠️ Errors Observed

1. PDF Worker Error

Warning: Setting up fake worker.
Error: Setting up fake worker failed: Failed to resolve module specifier 'pdf.worker.mjs'

2. File Load Error

Failed to load resource: the server responded with a status of 404

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🧠 Understanding the Issue

• The PDF viewer (PDF.js via react-pdf) requires a web worker (pdf.worker.mjs) to process PDF files efficiently.
• Currently, the worker file is not being resolved correctly by the bundler (Vite/Webpack).
• As a fallback, the system tries to use a fake worker, which also fails — resulting in the error.

Additionally:

• Some PDF URLs are returning 404 errors, meaning the file is either:

  • Not available on the server
  • Incorrectly referenced
  • Not properly served via API/static path

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🔍 Root Causes

• Missing or incorrect configuration of pdfjs.GlobalWorkerOptions.workerSrc
• Incorrect bundler handling of .mjs worker file
• pdfjs-dist not properly installed or referenced
• Invalid or broken PDF file URL

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✅ Proposed Fix

1. Fix Worker Setup (Frontend)

import { pdfjs } from "react-pdf";
import worker from "pdfjs-dist/build/pdf.worker?url";

pdfjs.GlobalWorkerOptions.workerSrc = worker;

2. Verify Dependency

npm install pdfjs-dist

3. Fix PDF URL Issue

• Validate API response for correct file URL
• Ensure file is accessible via browser
• Check backend/static file serving configuration

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🎯 Expected Outcome

• PDF loads without warnings
• No fallback to fake worker
• Improved performance (worker-based rendering)
• No 404 errors for PDF files