better resistance of NetworkImage generation against heavy load

this is needed for the network image on the yacy.net home page

git-svn-id: https://svn.berlios.de/svnroot/repos/yacy/trunk@7046 6c8d7289-2bf4-0310-a012-ef5d649a1542

1 files changed, 9 insertions, 2 deletions

diff --git a/htroot/NetworkPicture.java b/htroot/NetworkPicture.java
index 69d327a36..3d62a22f6 100644
--- a/htroot/NetworkPicture.java
+++ b/htroot/NetworkPicture.java
@@ -24,6 +24,8 @@
 // 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.concurrent.Semaphore;

+

 import de.anomic.http.server.RequestHeader;

 import de.anomic.search.Switchboard;

 import de.anomic.search.SwitchboardConstants;

@@ -35,7 +37,7 @@ import de.anomic.yacy.graphics.NetworkGraph;
 /** draw a picture of the yacy network */

 public class NetworkPicture {

     

-    private static final Object sync = new Object();

+    private static final Semaphore sync = new Semaphore(1);

     private static EncodedImage buffer = null;

     private static long lastAccessSeconds = 0;

     

@@ -48,7 +50,9 @@ public class NetworkPicture {
             //System.out.println("*** NetworkPicture: cache hit (1)");

             return buffer;

         }

-        synchronized (sync) {

+        if (buffer != null && sync.availablePermits() == 0) return buffer;

+        try {

+            sync.acquire();

             if (buffer != null && !authorized  && timeSeconds - lastAccessSeconds < 2)  {

                 //System.out.println("*** NetworkPicture: cache hit (2)");

                 return buffer;

@@ -89,6 +93,9 @@ public class NetworkPicture {
             if (maxCount > 10000) maxCount = 10000;

             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;

+            sync.release();

+        } catch (InterruptedException e) {

+            if (sync.availablePermits() == 0) sync.release();

         }

         return buffer;

     }