better network image cache

git-svn-id: https://svn.berlios.de/svnroot/repos/yacy/trunk@7008 6c8d7289-2bf4-0310-a012-ef5d649a1542

htroot/NetworkPicture.java

@@ -24,8 +24,6 @@
 // along with this program; if not, write to the Free Software
 // Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 
-import java.util.TreeMap;
-
 import de.anomic.http.server.RequestHeader;
 import de.anomic.search.Switchboard;
 import de.anomic.search.SwitchboardConstants;
@@ -37,19 +35,24 @@ import de.anomic.yacy.graphics.NetworkGraph;
 /** draw a picture of the yacy network */
 public class NetworkPicture {
     
-    private static final TreeMap<Long, EncodedImage> buffer = new TreeMap<Long, EncodedImage>();
+    private static final Object sync = new Object();
+    private static EncodedImage buffer = null;
+    private static long lastAccessSeconds = 0;
     
     public static EncodedImage respond(final RequestHeader header, final serverObjects post, final serverSwitch env) {
         final Switchboard sb = (Switchboard) env;
         final boolean authorized = sb.adminAuthenticated(header) >= 2;
         
         long timeSeconds = System.currentTimeMillis() / 1000;
-        EncodedImage bufferedImage = null;
-        synchronized (buffer) {
-            bufferedImage = buffer.get(timeSeconds);
+        if (buffer != null && timeSeconds - lastAccessSeconds < 2) {
+            //System.out.println("*** NetworkPicture: cache hit (1)");
+            return buffer;
+        }
+        synchronized (sync) {
+            if (buffer != null && timeSeconds - lastAccessSeconds < 2)  {
+                //System.out.println("*** NetworkPicture: cache hit (2)");
+                return buffer;
             }
-        if (bufferedImage != null) return bufferedImage;
-        
             int width = 768;
             int height = 576;
             int passiveLimit = 720; // 12 hours
@@ -84,12 +87,10 @@ public class NetworkPicture {
             if (passiveLimit > 1000000) passiveLimit = 1000000;
             if (potentialLimit > 1000000) potentialLimit = 1000000;
             if (maxCount > 10000) maxCount = 10000;
-        bufferedImage = new EncodedImage(NetworkGraph.getNetworkPicture(sb.peers, 10000, width, height, passiveLimit, potentialLimit, maxCount, coronaangle, communicationTimeout, env.getConfig(SwitchboardConstants.NETWORK_NAME, "unspecified"), env.getConfig("network.unit.description", "unspecified"), bgcolor).getImage(), "png");
-        synchronized (buffer) {
-            buffer.put(timeSeconds, bufferedImage);
-            while (buffer.size() > 8) buffer.remove(buffer.firstKey());
+            buffer = new EncodedImage(NetworkGraph.getNetworkPicture(sb.peers, 10000, width, height, passiveLimit, potentialLimit, maxCount, coronaangle, communicationTimeout, env.getConfig(SwitchboardConstants.NETWORK_NAME, "unspecified"), env.getConfig("network.unit.description", "unspecified"), bgcolor).getImage(), "png");
+            lastAccessSeconds = System.currentTimeMillis() / 1000;
         }
-        return bufferedImage;
+        return buffer;
     }
     
 }