Ryan BrownOne of the most frustrating classes of bugs is the kind where nothing changed—yet something suddenly stops working.
That’s exactly what happened to a customer using cfhtmltopdf() to generate PDFs on the fly. The code had been stable, unchanged, and reliable for months. Then, seemingly overnight, users began reporting errors saying the system could not find the generated PDF file.
At first glance, it looked like a file-path or application bug. In reality, it was something deeper—and far more subtle.
Overview
A customer running ColdFusion on a VPS reported that dynamic PDF generation had stopped working across their application. The PDFs were generated on demand by:
- Creating an HTML file
- Passing that HTML file into cfhtmltopdf()
- Writing the resulting PDF to disk
Instead of producing a PDF, ColdFusion began throwing file-not-found errors—even though the HTML source file existed and no code changes had been made.
This raised an important question:
What breaks cfhtmltopdf() when the code hasn’t changed?
The Challenge
There were several misleading signals:
- ❌ The error message pointed to a missing PDF file
- ❌ The HTML source file did exist
- ❌ The same failure occurred across multiple PDFs
- ❌ The issue appeared suddenly, without deployments or edits
That combination often leads teams down the wrong path—debugging file permissions, paths, or string handling—when the real issue is below the application layer.
The customer correctly suspected the problem might be ColdFusion itself, not the code.
Investigation Findings
When we reviewed the server, we discovered that:
- ColdFusion’s PDF Service was failing internally
- Each attempt to generate a PDF triggered a generic:
“Error occurred while generating PDF”
- The failure began after a ColdFusion update cycle, not after application changes
This aligned with a known issue in ColdFusion 2023 Update 13, where PDF generation could silently fail while still allowing HTML output to succeed.
In other words:
- cfhtmltopdf() was being called correctly
- The source HTML was valid
- The destination path was correct
…but the underlying PDF engine was broken.
The Solution
The fix was not a code change.
Adobe had already resolved this issue in later updates to Adobe ColdFusion.
What we did:
- Applied the latest ColdFusion 2023 updates (Update 16)
- Restarted ColdFusion services during an approved maintenance window
- Re-tested dynamic PDF generation across multiple workflows
Immediately after the update, PDFs began generating normally again—using the same code that had previously failed.
Important Update Note
(That Could Have Broken Code—but Didn’t)
ColdFusion Update 15 introduced a change related to remote CFC method invocation:
- Remote methods must explicitly declare expected arguments using cfargument or function signatures
In this case:
- The customer’s codebase was already compliant
- No regressions were observed
- No remediation was required
This is a good example of why reading update notes matters, even when the visible problem seems unrelated.
The xByte Cloud Difference
This incident highlights a critical but often-overlooked reality:
When ColdFusion breaks, it doesn’t always fail loudly—or honestly.
A PDF service failure can masquerade as:
- missing files
- bad paths
- broken logic
- user error
Without platform-level visibility, teams waste hours debugging perfectly good code.
Our role isn’t just to host ColdFusion—it’s to:
- track known Adobe defects
- correlate symptoms with update histories
- apply fixes safely during customer-approved windows
- explain why something broke, not just how it was fixed
Results
- ✅ PDF generation fully restored
- ✅ No application code changes required
- ✅ Known ColdFusion defect resolved
- ✅ Customer-confirmed fix across all workflows
Most importantly, the customer regained confidence that the issue was understood—not just patched.
