Ben created FOP-3313:
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Summary: Multi-threaded FOP usage breaks FontLoader
Key: FOP-3313
URL: https://issues.apache.org/jira/browse/FOP-3313
Project: FOP
Issue Type: Bug
Components: unqualified
Affects Versions: 2.4
Reporter: Ben
I'm trying to convert our usage of Apache FOP from a single-threaded
implementation to a multi-threaded one.
We have a process that generates PDF documents for every item in a large
dataset, and this is creating a performance bottleneck: each item takes about
200ms to generate using FOP in out single-threaded implementation.
The wrapper class by which we use FOP, FopConfiguration, declares a
{{FopFactory}} field. I've now converted it to a {{{}private
ThreadLocal<FopFactory> factory{}}}.
I have a font directory that the FOP factory needs to load custom fonts from.
This directory is initialised once, and then passed to the code that
instantiates the ThreadLocal.
I would expect switching to ThreadLocal for the FopFactory would be sufficient,
but what I'm instead seeing is that when {{agent.newFop}} is called, it's
causing {{org.apache.fop.fonts.FontLoader#read}} to be called within that
thread.
There seems to be some resource contention within that method, because in
contrast to the single-threaded wrapper, the multi-threaded wrapper is failing
at {{OpenFont.readCMAP}} with the following error:
Unsupported TrueType font: No Unicode or Symbol cmap table not present. Aborting
So it seems like the FOP agent is lazy-loading some fonts, and doing so isn't
thread-safe?
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