Understanding IronPdfEngine in IronPDF for Node.js
IronPDF for Node.js does its rendering through IronPdfEngine. Knowing how the engine starts and how it scales explains the limits you hit when running more than one instance on a machine.
Default behavior
By default, IronPDF for Node.js spawns a subprocess that talks to IronPdfEngine over gRPC on port 33350. The engine runs locally and is tied to that port.
Because the port is fixed by default, running two applications that use IronPDF on the same machine is not allowed without changing it. Give each application instance its own engine port when you need to run more than one side by side.
Scaling
IronPdfEngine itself cannot be scaled horizontally: loaded PDF data lives in memory and cannot be shared between engine instances. Scale the engine vertically instead, by giving the instance more resources.
The application can still scale horizontally. Pull IronPdfEngine from Docker and connect multiple application instances to it, or dockerize the app and run each horizontally scaled instance in its own isolated container under the default behavior.
Summary
- IronPDF for Node.js spawns a subprocess that communicates with IronPdfEngine over gRPC on port
33350. - Running multiple app instances on one machine requires a different engine port for each instance.
- Instead of the default, you can pull IronPdfEngine from Docker and connect several application instances to it.
- IronPdfEngine cannot scale horizontally; scale it vertically, or horizontally scale the application and let each instance run in its own isolated container.
Curtis Chau holds a Bachelor’s degree in Computer Science (Carleton University) and specializes in front-end development with expertise in Node.js, TypeScript, JavaScript, and React. Passionate about crafting intuitive and aesthetically pleasing user interfaces, Curtis enjoys working with modern frameworks and creating well-structured, visually appealing manuals.
