We are using ChartFX 7 for Java to make charts that are refreshing every second. An example provided by SoftwareFX for refreshing the chart made out of a query to a db is shown in the code that follows. We came accross the following problem, inside the chartfx70/temp directory there are the PNG and the CHS files that are created for each chart, while updating the chart the chartfx server creates new PNG & CHS files and never releases the resources. With 2 charts per page and 1 second refresh rates and 15 users we have a total of 108000 files/hour. After a few hours we end up with a huge amount of open files that in windows slows down the application and in linux we have problems with the open files limit of the kernel (see lsof, ulimit).
One answer was to write a script that deletes the files, but even after deleting the files the file handles in the kernel are still all taken and no new files can be opened. How should we instruct the chart server to release the resources after the update is executed ?
Code for charts that update provided by SoftwareFX Suport:
<%@page import="com.softwarefx.chartfx.server.*"%> <%@page import="com.softwarefx.chartfx.server.dataproviders.*"%> <%@page contentType="text/html" pageEncoding="UTF-8"%> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>Passing Data: JDBC</title> </head> <script LANGUAGE = "JavaScript"> var ascendent = true; var timerID = null var delay = 5000 function InitializeTimer() { StartTheTimer() } function StartTheTimer() { var param = ""; if (ascendent) param = "asc"; else param = "desc"; SFX_processing = false; SFX_SendUserCallback('chart1', param, false); ascendent = !ascendent; timerID = self.setTimeout("StartTheTimer()", delay) } function SFX_UpdateControls(id,callbackReturn) { if (callbackReturn != "") alert(callbackReturn); } </SCRIPT> <body> <input type="submit" name="Button1" value="Start" id="Button1" style="font-family: Arial; font-size: 9pt; width: 56px;" onclick="InitializeTimer()"/> <%! public class UserCallBackEventHandler implements com.softwarefx.chartfx.server.UserCallbackListener { public void userCallbackEventHandler(UserCallbackEvent e) { ChartServer chart1 = (ChartServer) e.getSource(); chart1.getDataSourceSettings().getFields().clear(); java.sql.ResultSet rs = null; java.sql.Connection conn = null; String query = "SELECT * FROM SampleFinancial ORDER BY Field1 " + e.getParam(); try { Class.forName("org.hsqldb.jdbcDriver"); String database = "jdbc:hsqldb:file:" + getServletContext().getRealPath("/") + "/data/sampledb/sampledb"; conn = java.sql.DriverManager.getConnection(database, "SA", ""); java.sql.Statement stmt = conn.createStatement(); rs = stmt.executeQuery(query); } catch (Exception ex) { } JDBCDataProvider provider = new JDBCDataProvider(rs); chart1.getDataSourceSettings().getFields().add(new FieldMap("Field1", FieldUsage.LABEL)); chart1.getDataSourceSettings().getFields().add(new FieldMap("Field2", FieldUsage.VALUE)); chart1.getDataSourceSettings().getFields().add(new FieldMap("Field3", FieldUsage.VALUE)); chart1.getDataSourceSettings().setDataSource(provider); try { conn.close(); } catch (Exception ex) { } chart1.recalculateScale(); } } %> <% ChartServer chart1 = new ChartServer(pageContext, request, response); chart1.setID("chart1"); chart1.setUseCallbacksForEvents(true); chart1.addUserCallbackListener(new UserCallBackEventHandler()); chart1.setWidth(600); chart1.setHeight(400); java.sql.ResultSet rs = null; java.sql.Connection conn = null; String query = ""; try { Class.forName("org.hsqldb.jdbcDriver"); String database = "jdbc:hsqldb:file:" + application.getRealPath("/") + "/data/sampledb/sampledb"; conn = java.sql.DriverManager.getConnection(database, "SA", ""); java.sql.Statement stmt = conn.createStatement(); query = "SELECT * FROM SampleFinancial"; rs = stmt.executeQuery(query); } catch (Exception e) { out.println(e.getMessage()); } JDBCDataProvider provider = new JDBCDataProvider(rs); chart1.getDataSourceSettings().getFields().add(new FieldMap("Field1", FieldUsage.LABEL)); chart1.getDataSourceSettings().getFields().add(new FieldMap("Field2", FieldUsage.VALUE)); chart1.getDataSourceSettings().getFields().add(new FieldMap("Field3", FieldUsage.VALUE)); chart1.getDataSourceSettings().setDataSource(provider); conn.close(); chart1.getAxisX().getLabelsFormat().setFormat(AxisFormat.DATE); SeriesAttributes series0 = chart1.getSeries().get(0); series0.setGallery(Gallery.LINES); series0.getLine().setWidth((short) 2); series0.setMarkerShape(MarkerShape.NONE); series0.setAxisY(chart1.getAxisY()); SeriesAttributes series1 = chart1.getSeries().get(1); series1.setGallery(Gallery.AREA); series1.getBorder().setVisible(true); series1.setAxisY(chart1.getAxisY2()); chart1.getAxisY().getGrids().getMajor().setVisible(true); Axis axis = chart1.getAxisY2(); axis.setMax(200000000); axis.setMin(0); axis.setVisible(false); chart1.getPlotAreaMargin().setRight(30); chart1.recalculateScale(); chart1.getSeries().get(0).setText("Price"); chart1.getSeries().get(1).setText("Volume"); chart1.renderControl(); %> </body> </html>
