optimize DefaultTpsLimiter

dubbo-rpc/dubbo-rpc-api/src/main/java/org/apache/dubbo/rpc/filter/tps/DefaultTPSLimiter.java

@@ -46,6 +46,13 @@ public boolean isAllowable(URL url, Invocation invocation) {
                 stats.putIfAbsent(serviceKey,
                         new StatItem(serviceKey, rate, interval));
                 statItem = stats.get(serviceKey);
+            } else {
+                //rate has changed, rebuild
+                if (statItem.getRate() != rate) {
+                    stats.put(serviceKey,
+                            new StatItem(serviceKey, rate, interval));
+                    statItem = stats.get(serviceKey);
+                }
             }
             return statItem.isAllowable();
         } else {

dubbo-rpc/dubbo-rpc-api/src/main/java/org/apache/dubbo/rpc/filter/tps/StatItem.java

@@ -16,7 +16,7 @@
  */
 package org.apache.dubbo.rpc.filter.tps;
 
-import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.atomic.LongAdder;
 
 /**
  * Judge whether a particular invocation of service provider method should be allowed within a configured time interval.
@@ -30,7 +30,7 @@ class StatItem {
 
     private long interval;
 
-    private AtomicInteger token;
+    private LongAdder token;
 
     private int rate;
 
@@ -39,32 +39,35 @@ class StatItem {
         this.rate = rate;
         this.interval = interval;
         this.lastResetTime = System.currentTimeMillis();
-        this.token = new AtomicInteger(rate);
+        this.token = buildLongAdder(rate);
     }
 
     public boolean isAllowable() {
         long now = System.currentTimeMillis();
         if (now > lastResetTime + interval) {
-            token.set(rate);
+            token = buildLongAdder(rate);
             lastResetTime = now;
         }
 
-        int value = token.get();
         boolean flag = false;
-        while (value > 0 && !flag) {
-            flag = token.compareAndSet(value, value - 1);
-            value = token.get();
+        while (getToken() > 0 && !flag) {
+            token.decrement();
+            flag = true;
         }
 
         return flag;
     }
 
+    public int getRate() {
+        return rate;
+    }
+
     long getLastResetTime() {
         return lastResetTime;
     }
 
-    int getToken() {
-        return token.get();
+    long getToken() {
+        return token.sum();
     }
 
     @Override
@@ -76,4 +79,10 @@ public String toString() {
                 .toString();
     }
 
+    private LongAdder buildLongAdder(int rate) {
+        LongAdder adder = new LongAdder();
+        adder.add(rate);
+        return adder;
+    }
+
 }