[PDFBOX-3080] TrueTypeFont synchronization

• Type: Improvement
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 2.0.0
• Fix Version/s: 3.0.0 PDFBox
• Component/s: FontBox
• Labels: Optimization multithreading
• Environment: Debian, java version "1.8.0_60"; Java(TM) SE Runtime Environment (build 1.8.0_60-b27); Java HotSpot(TM) 64-Bit Server VM (build 25.60-b23, mixed mode)
• Assignee: Andreas Lehmkühler
• Reporter: ccouturi
• Created: 02/Nov/15 13:40
• Updated: 18/Aug/23 05:46
• Resolved: 03/Nov/20 16:46

Description

The use case is rasterize pdf to png.

On high load, a lot of threads are blocked in the TrueTypeFont.getHorizontalMetrics() or getHorinzontalHeader() methods.

Jstack snippet:

Thread 21999: (state = BLOCKED)
 - org.apache.fontbox.ttf.TrueTypeFont.getHorizontalMetrics() @bci=6, line=231 (Compiled frame)
 - org.apache.fontbox.ttf.TrueTypeFont.getAdvanceWidth(int) @bci=1, line=439 (Compiled frame)
 - org.apache.pdfbox.pdmodel.font.PDTrueTypeFont.getWidthFromFont(int) @bci=11, line=324 (Compiled frame)
 - org.apache.pdfbox.rendering.PageDrawer.drawGlyph2D(org.apache.pdfbox.rendering.Glyph2D, org.apache.pdfbox.pdmodel.font.PDFont, int, org.apache.pdfbox.util.Vector, java.awt.geom.AffineTransform)
 @bci=39, line=350 (Compiled frame)
 - org.apache.pdfbox.rendering.PageDrawer.showFontGlyph(org.apache.pdfbox.util.Matrix, org.apache.pdfbox.pdmodel.font.PDFont, int, java.lang.String, org.apache.pdfbox.util.Vector) @bci=34, line=32
5 (Compiled frame)
 - org.apache.pdfbox.contentstream.PDFStreamEngine.showGlyph(org.apache.pdfbox.util.Matrix, org.apache.pdfbox.pdmodel.font.PDFont, int, java.lang.String, org.apache.pdfbox.util.Vector) @bci=32, li
ne=728 (Compiled frame)
 - org.apache.pdfbox.contentstream.PDFStreamEngine.showText(byte[]) @bci=240, line=685 (Compiled frame)
 - org.apache.pdfbox.contentstream.PDFStreamEngine.showTextString(byte[]) @bci=2, line=553 (Compiled frame)
 - org.apache.pdfbox.contentstream.operator.text.ShowText.process(org.apache.pdfbox.contentstream.operator.Operator, java.util.List) @bci=45, line=50 (Compiled frame)
 - org.apache.pdfbox.contentstream.PDFStreamEngine.processOperator(org.apache.pdfbox.contentstream.operator.Operator, java.util.List) @bci=35, line=799 (Compiled frame)
 - org.apache.pdfbox.contentstream.PDFStreamEngine.processStreamOperators(org.apache.pdfbox.contentstream.PDContentStream) @bci=69, line=461 (Compiled frame)
 - org.apache.pdfbox.contentstream.PDFStreamEngine.processStream(org.apache.pdfbox.contentstream.PDContentStream) @bci=63, line=438 (Compiled frame)
 - org.apache.pdfbox.contentstream.PDFStreamEngine.showForm(org.apache.pdfbox.pdmodel.graphics.form.PDFormXObject) @bci=19, line=178 (Interpreted frame)
 - org.apache.pdfbox.contentstream.operator.graphics.DrawObject.process(org.apache.pdfbox.contentstream.operator.Operator, java.util.List) @bci=162, line=70 (Interpreted frame)
 - org.apache.pdfbox.contentstream.PDFStreamEngine.processOperator(org.apache.pdfbox.contentstream.operator.Operator, java.util.List) @bci=35, line=799 (Compiled frame)
 - org.apache.pdfbox.contentstream.PDFStreamEngine.processStreamOperators(org.apache.pdfbox.contentstream.PDContentStream) @bci=69, line=461 (Compiled frame)
 - org.apache.pdfbox.contentstream.PDFStreamEngine.processStream(org.apache.pdfbox.contentstream.PDContentStream) @bci=63, line=438 (Compiled frame)
 - org.apache.pdfbox.contentstream.PDFStreamEngine.processPage(org.apache.pdfbox.pdmodel.PDPage) @bci=19, line=149 (Interpreted frame)
 - org.apache.pdfbox.rendering.PageDrawer.drawPage(java.awt.Graphics, org.apache.pdfbox.pdmodel.common.PDRectangle) @bci=93, line=180 (Interpreted frame)
 - org.apache.pdfbox.rendering.PDFRenderer.renderPage(org.apache.pdfbox.pdmodel.PDPage, java.awt.Graphics2D, int, int, float, float) @bci=160, line=208 (Interpreted frame)
 - org.apache.pdfbox.rendering.PDFRenderer.renderImage(int, float, org.apache.pdfbox.rendering.ImageType) @bci=166, line=139 (Interpreted frame)
 - org.apache.pdfbox.rendering.PDFRenderer.renderImageWithDPI(int, float, org.apache.pdfbox.rendering.ImageType) @bci=7, line=94 (Interpreted frame)
[...]

These methods are synchronized. (I think because of initialization block.)

When I change from:

actual

public synchronized HorizontalHeaderTable getHorizontalHeader() throws IOException {
    HorizontalHeaderTable horizontalHeader = (HorizontalHeaderTable)tables.get( HorizontalHeaderTable.TAG );
    if (horizontalHeader != null && !horizontalHeader.getInitialized()) {
        readTable(horizontalHeader);
    }
    return horizontalHeader;
 }

to:

patch

public HorizontalHeaderTable getHorizontalHeader() throws IOException {
    HorizontalHeaderTable horizontalHeader = (HorizontalHeaderTable) tables.get(HorizontalHeaderTable.TAG);
    if (horizontalHeader != null && !horizontalHeader.getInitialized()) {
        synchronized (this) {
            if (!horizontalHeader.getInitialized()) {
                readTable(horizontalHeader);
            }
        }
     }
     return horizontalHeader;
 }

the lock disappears.