reduce synchronization, cleanup code

jpos/src/main/java/org/jpos/util/ThroughputControl.java

@@ -19,6 +19,7 @@
 package org.jpos.util;
 
 import java.time.Instant;
+import java.util.concurrent.atomic.AtomicInteger;
 
 /**
  * ThroughputControl limits the throughput 
@@ -42,70 +43,79 @@
 public class ThroughputControl {
     private int[] period;
     private int[] max;
-    private int[] cnt;
+    private AtomicInteger[] cnt;
     private long[] start;
     private long[] sleep;
+    private static final long MIN_SLEEP = 50L;
+    private static final long MAX_SLEEP = 500L;
 
     /**
-     * @param maxTransactions ditto
-     * @param periodInMillis ditto
+     * @param maxTransactions Maximum number of transactions allowed.
+     * @param periodInMillis Duration (in milliseconds) over which the maximum is calculated.
      */
     public ThroughputControl (int maxTransactions, int periodInMillis) {
         this (new int[] { maxTransactions },
               new int[] { periodInMillis });
     }
     /**
-     * @param maxTransactions ditto
-     * @param periodInMillis ditto
+     * @param maxTransactions Array of maximum transactions allowed for each period.
+     * @param periodInMillis Array of periods (in milliseconds) corresponding to each maximum.
      */
     public ThroughputControl (int[] maxTransactions, int[] periodInMillis) {
         super();
         int l = maxTransactions.length;
         period = new int[l];
         max = new int[l];
-        cnt = new int[l];
+        cnt = new AtomicInteger[l];
         start = new long[l];
         sleep = new long[l];
         for (int i=0; i<l; i++) {
             this.max[i]    = maxTransactions[i];
             this.period[i] = periodInMillis[i];
-            this.sleep[i]  = Math.min(Math.max (periodInMillis[i]/10, 500L),50L);
+            // Calculate sleep time, ensuring it is within the defined minimum and maximum bounds.
+            this.sleep[i]  = Math.min(Math.max(periodInMillis[i] / 10, MIN_SLEEP), MAX_SLEEP);
             this.start[i]  = Instant.now().toEpochMilli();
+            this.cnt[i] = new AtomicInteger(0);
         }
     }
 
     /**
      * control should be called on every transaction.
      * it may sleep for a while in order to control the system throughput
-     * 
+     *
      * @return aprox sleep time or zero if no sleep
      */
     public long control() {
         boolean delayed = false;
         long init = Instant.now().toEpochMilli();
-        for (int i=0; i<cnt.length; i++) {
-            synchronized (this) {
-                cnt[i]++;
-            }
-            do {
-                if (cnt[i] > max[i]) {
-                    delayed = true;
-                    try { 
-                        Thread.sleep (sleep[i]); 
-                    } catch (InterruptedException e) { }
-                }
-                synchronized (this) {
-                    long now = Instant.now().toEpochMilli();
-                    if (now - start[i] > period[i]) {
-                        long elapsed = now - start[i];
-                        int  allowed = (int) (elapsed * max[i] / period[i]);
-                        start[i] = now;
-                        cnt[i] = Math.max (cnt[i] - allowed, 0);
+        for (int i = 0; i < cnt.length; i++) {
+            if (cnt[i].incrementAndGet() > max[i]) {
+                delayed = true;
+                while (cnt[i].get() > max[i]) {
+                    try {
+                        Thread.sleep(sleep[i]);
+                    } catch (InterruptedException e) {
+                        Thread.currentThread().interrupt();
                     }
+
+                    checkAndReset(i);
                 }
-            } while (cnt[i] > max[i]);
+            }
         }
         return delayed ? Instant.now().toEpochMilli() - init : 0L;
     }
-}
 
+    private synchronized void checkAndReset(int i) {
+        long now = Instant.now().toEpochMilli();
+        if (now - start[i] > period[i]) {
+            long elapsed = now - start[i];
+            int allowed = (int) (elapsed * max[i] / period[i]);
+            start[i] = now;
+            cnt[i].addAndGet(-allowed);
+
+            if (cnt[i].get() < 0) {
+                cnt[i].set(0);
+            }
+        }
+    }
+}