Hi fop-dev,
In one of my use cases, I create a PDF file having about 20000 pages from FOP
intermediate format. I imagined this as a streaming process (e.g. read a page
in FOP_IF, write it to PDF and release memory) with the exception of caching of
images. In reality, by analyzing a heap dump taken with the
-XX:+HeapDumpOnOutOfMemoryError parameter on a production server, I found out
that o.a.f.r.p.PDFDocumentHandler keeps for every page a reference to be used
for bookmarks & outlines. In my case, the retained heap size of every page is
about 150kb. If you multiply this with the number of pages, the memory usage is
large. Even worse, on my production server I have 10 threads creating 20k page
documents in parallel.
Attached is a patch against the latest revision 1051938 of trunk that
considerably reduces the memory usage by keeping only a String pdfPageRef
instead of the full org.apache.fop.pdf.PDFReference object. This was possible
because from the object we only need to get that string. Ideally, I would like
not to keep at all the page references if bookmarks & outlines are not used. Or
at least, keep it only for the pages that are indeed referenced. Is this
possible ? If so, do you have any hints for this ?
If further optimizations are not possible or complex, then I guess I will just
open an issue and attach this patch. I hope you agree with the addition of
generics on the Map declaration and with the change of "new Integer()" to
"Integer.valueOf())" (findbugs performance warning).
Greetings,
Alexis Giotis
Index: src/java/org/apache/fop/render/pdf/PDFDocumentHandler.java
===================================================================
--- src/java/org/apache/fop/render/pdf/PDFDocumentHandler.java (revision
1051938)
+++ src/java/org/apache/fop/render/pdf/PDFDocumentHandler.java (working copy)
@@ -39,7 +39,6 @@
import org.apache.fop.pdf.PDFAnnotList;
import org.apache.fop.pdf.PDFDocument;
import org.apache.fop.pdf.PDFPage;
-import org.apache.fop.pdf.PDFReference;
import org.apache.fop.pdf.PDFResourceContext;
import org.apache.fop.pdf.PDFResources;
import org.apache.fop.render.extensions.prepress.PageBoundaries;
@@ -93,7 +92,7 @@
protected PageReference currentPageRef;
/** Used for bookmarks/outlines. */
- protected Map pageReferences = new java.util.HashMap();
+ protected Map<Integer, PageReference> pageReferences = new
java.util.HashMap<Integer, PageReference>();
private final PDFDocumentNavigationHandler documentNavigationHandler
= new PDFDocumentNavigationHandler(this);
@@ -238,7 +237,7 @@
pdfUtil.generatePageLabel(index, name);
currentPageRef = new PageReference(currentPage, size);
- this.pageReferences.put(new Integer(index), currentPageRef);
+ this.pageReferences.put(Integer.valueOf(index), currentPageRef);
this.generator = new PDFContentGenerator(this.pdfDoc,
this.outputStream,
this.currentPage);
@@ -308,21 +307,22 @@
}
PageReference getPageReference(int pageIndex) {
- return (PageReference)this.pageReferences.get(
- new Integer(pageIndex));
+ return this.pageReferences.get(Integer.valueOf(pageIndex));
}
static final class PageReference {
- private final PDFReference pageRef;
+ private final String pageRef;
private final Dimension pageDimension;
private PageReference(PDFPage page, Dimension dim) {
- this.pageRef = page.makeReference();
+ // Avoid keeping references to PDFPage as memory usage is
+ // considerably increased when handling thousands of pages.
+ this.pageRef = page.makeReference().toString();
this.pageDimension = new Dimension(dim);
}
- public PDFReference getPageRef() {
+ public String getPageRef() {
return this.pageRef;
}
Index: src/java/org/apache/fop/render/pdf/PDFDocumentNavigationHandler.java
===================================================================
--- src/java/org/apache/fop/render/pdf/PDFDocumentNavigationHandler.java
(revision 1051938)
+++ src/java/org/apache/fop/render/pdf/PDFDocumentNavigationHandler.java
(working copy)
@@ -189,7 +189,7 @@
p2d = new Point2D.Double(
action.getTargetLocation().x / 1000.0,
(pageRef.getPageDimension().height -
action.getTargetLocation().y) / 1000.0);
- String pdfPageRef = pageRef.getPageRef().toString();
+ String pdfPageRef = pageRef.getPageRef();
pdfGoTo.setPageReference(pdfPageRef);
pdfGoTo.setPosition(p2d);
