Fixed a memory-leak: The FO tree part of a page-sequence was not released when a page-sequence was finished.

Added a "MemoryEater" debug helper which can replicate page-sequences of a regular FO file using the fo-replicator.xsl. Without the fix a JVM set to the normal 64MB heap size throws an OutOfMemoryError when replicating readme.fo 150 times. With the fix the memory consumption doesn't go above 10MB for the 1350 pages. Note that about one third of the time goes into garbage collection.


git-svn-id: https://svn.apache.org/repos/asf/xmlgraphics/fop/trunk@428450 13f79535-47bb-0310-9956-ffa450edef68

src/java/org/apache/fop/fo/pagination/PageSequence.java

@@ -539,4 +539,12 @@ public class PageSequence extends FObj {
         return this.language;
     }
 
+    /**
+     * Releases a page-sequence's children after the page-sequence has been fully processed.
+     */
+    public void releasePageSequence() {
+        this.mainFlow = null;
+        this.flowMap.clear();
+    }
+    
 }

src/java/org/apache/fop/layoutmgr/PageSequenceLayoutManager.java

@@ -168,6 +168,7 @@ public class PageSequenceLayoutManager extends AbstractLayoutManager {
                 (currentPageNum - startPageNum) + 1);
         areaTreeHandler.notifyPageSequenceFinished(pageSeq,
                 (currentPageNum - startPageNum) + 1);
+        pageSeq.releasePageSequence();
         log.debug("Ending layout");
     }
 

status.xml

@@ -28,6 +28,10 @@
 
   <changes>
     <release version="FOP Trunk">
+      <action context="Code" dev="JM" type="fix">
+        Fixed a memory-leak: The FO tree part of a page-sequence was not released when a
+        page-sequence was finished.
+      </action>
       <action context="Code" dev="JM" type="fix">
         Bugfix: Table headers and footers were swallowed when a table was nested in a list-block.
       </action>

test/java/org/apache/fop/memory/MemoryEater.java

@@ -0,0 +1,108 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ * 
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ * 
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/* $Id$ */
+
+package org.apache.fop.memory;
+
+import java.io.BufferedReader;
+import java.io.File;
+import java.io.IOException;
+import java.io.OutputStream;
+
+import javax.xml.transform.Result;
+import javax.xml.transform.Source;
+import javax.xml.transform.Transformer;
+import javax.xml.transform.sax.SAXResult;
+import javax.xml.transform.sax.SAXTransformerFactory;
+import javax.xml.transform.stream.StreamSource;
+
+import org.apache.commons.io.output.NullOutputStream;
+import org.apache.fop.apps.Fop;
+import org.apache.fop.apps.FopFactory;
+import org.apache.fop.apps.MimeConstants;
+
+/**
+ * Debug tool to create and process large FO files by replicating them a specified number of times.
+ */
+public class MemoryEater {
+
+    private static void eatMemory(File foFile, int replicatorRepeats) throws Exception {
+
+        SAXTransformerFactory tFactory = (SAXTransformerFactory)SAXTransformerFactory.newInstance();
+        FopFactory fopFactory = FopFactory.newInstance();
+        
+        File xsltFile = new File("test/xsl/fo-replicator.xsl");
+        Source xslt = new StreamSource(xsltFile);
+        
+        Source src = new StreamSource(foFile);
+        
+        Transformer transformer = tFactory.newTransformer(xslt);
+        transformer.setParameter("repeats", new Integer(replicatorRepeats));
+        
+        OutputStream out = new NullOutputStream(); //write to /dev/nul
+        Fop fop = fopFactory.newFop(MimeConstants.MIME_PDF, out);
+        Result res = new SAXResult(fop.getDefaultHandler());
+        
+        transformer.transform(src, res);
+        
+        System.out.println("Generated " + fop.getResults().getPageCount() + " pages.");
+        
+    }
+
+    private static void prompt() throws IOException {
+        BufferedReader in = new BufferedReader(new java.io.InputStreamReader(System.in));
+        System.out.print("Press return to continue...");
+        in.readLine();
+    }
+    
+    /**
+     * Main method.
+     * @param args the command-line arguments
+     */
+    public static void main(String[] args) {
+        boolean doPrompt = true; //true if you want a chance to start the monitoring console
+        try {
+            int replicatorRepeats = 2;
+            if (args.length > 0) {
+                replicatorRepeats = Integer.parseInt(args[0]);
+            }
+            File testFile = new File("examples/fo/basic/readme.fo");
+            
+            System.out.println("MemoryEater! About to replicate the test file " 
+                    + replicatorRepeats + " times...");
+            if (doPrompt) {
+                prompt();
+            }
+            
+            System.out.println("Processing..."); 
+            long start = System.currentTimeMillis();
+            
+            eatMemory(testFile, replicatorRepeats);
+            
+            long duration = System.currentTimeMillis() - start;
+            System.out.println("Success! Job took " + duration + " ms");
+            
+            if (doPrompt) {
+                prompt();
+            }
+        } catch (Exception e) {
+            e.printStackTrace();
+        }
+    }
+
+}

test/xsl/fo-replicator.xsl

@@ -0,0 +1,72 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+  Licensed to the Apache Software Foundation (ASF) under one or more
+  contributor license agreements.  See the NOTICE file distributed with
+  this work for additional information regarding copyright ownership.
+  The ASF licenses this file to You under the Apache License, Version 2.0
+  (the "License"); you may not use this file except in compliance with
+  the License.  You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+-->
+<!-- $Id$ -->
+<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:fo="http://www.w3.org/1999/XSL/Format">
+  <xsl:param name="repeats" select="2"/>
+  <xsl:template match="@*|node()">
+    <xsl:param name="run"/>
+    <xsl:copy>
+      <xsl:apply-templates select="@*|node()">
+        <xsl:with-param name="run" select="$run"/>
+      </xsl:apply-templates>
+    </xsl:copy>
+  </xsl:template>
+  <xsl:template match="fo:root">
+    <fo:root>
+      <xsl:apply-templates select="@*|fo:layout-master-set|fo:declarations">
+        <xsl:with-param name="run" select="0"/>
+      </xsl:apply-templates>
+      <xsl:call-template name="repeat">
+        <xsl:with-param name="n" select="$repeats"/>
+        <xsl:with-param name="what" select="fo:page-sequence"/>
+      </xsl:call-template>
+    </fo:root>
+  </xsl:template>
+  <xsl:template name="repeat">
+    <xsl:param name="n"/>
+    <xsl:param name="what"/>
+    <xsl:if test="number($n) > 0">
+      <xsl:apply-templates select="$what">
+        <xsl:with-param name="run" select="$n"/>
+      </xsl:apply-templates>
+      <xsl:call-template name="repeat">
+        <xsl:with-param name="n" select="number($n) - 1"/>
+        <xsl:with-param name="what" select="$what"/>
+      </xsl:call-template>
+    </xsl:if>
+  </xsl:template>
+  <xsl:template match="@id">
+    <xsl:param name="run"/>
+    <xsl:attribute name="id"><xsl:value-of select="."/>-<xsl:value-of select="$run"/></xsl:attribute>
+  </xsl:template>
+  <xsl:template match="@ref-id">
+    <xsl:param name="run"/>
+    <xsl:attribute name="ref-id"><xsl:value-of select="."/>-<xsl:value-of select="$run"/></xsl:attribute>
+  </xsl:template>
+  <xsl:template match="@internal-destination">
+    <xsl:param name="run"/>
+    <xsl:attribute name="internal-destination"><xsl:value-of select="."/>-<xsl:value-of select="$run"/></xsl:attribute>
+  </xsl:template>
+  <xsl:template match="fo:page-number-citation">
+    <xsl:param name="run"/>
+    <fo:inline><xsl:value-of select="@ref-id"/></fo:inline>
+  </xsl:template>
+  <xsl:template match="fo:retrieve-marker|fo:marker">
+    <xsl:param name="run"/>
+  </xsl:template>
+</xsl:stylesheet>