added load and deadlock detector in Memory util

source/net/yacy/cora/util/Memory.java

@@ -20,6 +20,9 @@
 
 package net.yacy.cora.util;
 
+import java.lang.management.ManagementFactory;
+import java.lang.management.ThreadInfo;
+
 public class Memory {
 
     private static final Runtime runtime = Runtime.getRuntime();
@@ -45,7 +48,7 @@ public class Memory {
      * @return bytes
      */
     public static final long maxMemory() {
-        return runtime.maxMemory();
+        return runtime.maxMemory(); // can be Long.MAX_VALUE if unlimited
     }
 
     /**
@@ -63,5 +66,34 @@ public class Memory {
     public static final long used() {
         return total() - free();
     }
-
+    
+    /**
+     * get the system load within the last minute
+     * @return the system load or a negative number if the load is not available
+     */
+    public static double load() {
+        return ManagementFactory.getOperatingSystemMXBean().getSystemLoadAverage();
+    }
+    
+    /**
+     * find out the number of thread deadlocks. WARNING: this is a time-consuming task
+     * @return the number of deadlocked threads
+     */
+    public static long deadlocks() {
+        long[] deadlockIDs = ManagementFactory.getThreadMXBean().findDeadlockedThreads();
+        if (deadlockIDs == null) return 0;
+        return deadlockIDs.length;
+    }
+    
+    /**
+     * write deadlocked threads as to the log as warning
+     */
+    public static void logDeadlocks() {
+        long[] deadlockIDs = ManagementFactory.getThreadMXBean().findDeadlockedThreads();
+        if (deadlockIDs == null) return;
+        ThreadInfo[] infos = ManagementFactory.getThreadMXBean().getThreadInfo(deadlockIDs, true, true);
+        for (ThreadInfo ti : infos) {
+            ConcurrentLog.warn("DEADLOCKREPORT", ti.toString());
+        }
+    }
 }