[jira] [Commented] (PDFBOX-4963) TTF file leakage in font cache

["Kenichi Suzuki (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/PDFBOX-4963?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17622961#comment-17622961 ] 

Kenichi Suzuki commented on PDFBOX-4963:
----------------------------------------

Hey guys.
Is there a solution in this case?
Please let me know if you have a solution, even if it is tentative.
An actual example would be very helpful.
Also, has anyone tried this with other versions? (e.g., version
3)
Thank you in advance.

> TTF file leakage in font cache
> ------------------------------
>
>                 Key: PDFBOX-4963
>                 URL: https://issues.apache.org/jira/browse/PDFBOX-4963
>             Project: PDFBox
>          Issue Type: Bug
>          Components: PDModel
>    Affects Versions: 2.0.21
>            Reporter: Maison
>            Priority: Major
>
> We observe many TTF opened files in our production server, which result in exhausting file descriptors.
> We have checked and rechecked that every PDDocument is properly closed (try with resource everywhere).
> By looking at pdfbox source code, I suspect 2 problems in FontCache and in FileSystemFontProvider
> 1 - FontCache
> In FontCache, a map keeps SoftReference<FontBoxFont> as values.
> IIUC for TTF fonts, the values are instances of org.apache.fontbox.ttf.TrueTypeFont. Such instances have a TTFDataStream member, which is RAFDataStream (so there is an opened file).
> Problem is that if the soft reference is cleared by GC, we can suppose the TrueTypeFont objects are GCed (is that guaranteed?) ; but what about the RAFDataStream sub-object ? There is no RAFDataStream.close() in TrueTypeFont finalizer
> 2 - FileSystemFontProvider
> There seems to be a TOCTOU-like race condition when a font is needed. Code looks like below (simplified) :
>      @Override
>       public FontBoxFont getFont()
>        {
>           FontBoxFont cached = parent.cache.getFont(this);
>           if (cached != null) {
>                return cached;
>           }
>           FontBoxFont font = ... // instantiate font
>           parent.cache.addFont(this, font);  // <--- not thread safe ?
>           return font;
>     }
> The font, if not in cache, is instantiated and added into cache. But two threads can do that at the same time, and the last addFont() wins. So the first SoftReference<FontBoxFont> object is now eligible to GC; but the FontBoxFont has not been closed.
> This problem is probably less frequent.



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