End the 'read/write' combination operation early to improve performance (#15666)

Co-authored-by: zrlw <zrlw@sina.com>

Author: frozenNoob

dubbo-cluster/src/main/java/org/apache/dubbo/rpc/cluster/loadbalance/ConsistentHashLoadBalance.java

@@ -51,6 +51,13 @@ protected <T> Invoker<T> doSelect(List<Invoker<T>> invokers, URL url, Invocation
         String methodName = RpcUtils.getMethodName(invocation);
         String key = invokers.get(0).getUrl().getServiceKey() + "." + methodName;
         int invokersHashCode = invokers.hashCode();
+        // If the detection is successful, return in advance. it may be different from selector, but it doesn't matter
+        ConsistentHashSelector<T> oldSelector0;
+        if ((oldSelector0 = (ConsistentHashSelector<T>) selectors.get(key)) != null
+                && oldSelector0.identityHashCode == invokersHashCode) {
+            return oldSelector0.select(invocation);
+        }
+
         // using the hashcode of invoker list to create consistent selector by atomic computation.
         ConsistentHashSelector<T> selector = (ConsistentHashSelector<T>) selectors.compute(
                 key,