Fix warm up issue when provider's timestamp is bigger than local machine's timestamp. (apache#4870)

* Fix warm up issue when provider's timestamp is bigger than local machine's timestamp.

* Remove unused constant: `REMOTE_TIMESTAMP_KEY`.

Author: aftersss

dubbo-cluster/src/main/java/org/apache/dubbo/rpc/cluster/Constants.java

@@ -89,8 +89,6 @@ public interface Constants {
 
     String RUNTIME_KEY = "runtime";
 
-    String REMOTE_TIMESTAMP_KEY = "remote.timestamp";
-
     String WARMUP_KEY = "warmup";
 
     int DEFAULT_WARMUP = 10 * 60 * 1000;

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

@@ -24,9 +24,9 @@
 
 import java.util.List;
 
+import static org.apache.dubbo.common.constants.CommonConstants.TIMESTAMP_KEY;
 import static org.apache.dubbo.rpc.cluster.Constants.DEFAULT_WARMUP;
 import static org.apache.dubbo.rpc.cluster.Constants.DEFAULT_WEIGHT;
-import static org.apache.dubbo.rpc.cluster.Constants.REMOTE_TIMESTAMP_KEY;
 import static org.apache.dubbo.rpc.cluster.Constants.WARMUP_KEY;
 import static org.apache.dubbo.rpc.cluster.Constants.WEIGHT_KEY;
 
@@ -73,12 +73,18 @@ public <T> Invoker<T> select(List<Invoker<T>> invokers, URL url, Invocation invo
     int getWeight(Invoker<?> invoker, Invocation invocation) {
         int weight = invoker.getUrl().getMethodParameter(invocation.getMethodName(), WEIGHT_KEY, DEFAULT_WEIGHT);
         if (weight > 0) {
-            long timestamp = invoker.getUrl().getParameter(REMOTE_TIMESTAMP_KEY, 0L);
+            long timestamp = invoker.getUrl().getParameter(TIMESTAMP_KEY, 0L);
             if (timestamp > 0L) {
-                int uptime = (int) (System.currentTimeMillis() - timestamp);
+                long uptime = System.currentTimeMillis() - timestamp;
+                if (uptime >= Integer.MAX_VALUE) {
+                    return weight;
+                }
+                else if (uptime < 0) {
+                    return 1;
+                }
                 int warmup = invoker.getUrl().getParameter(WARMUP_KEY, DEFAULT_WARMUP);
                 if (uptime > 0 && uptime < warmup) {
-                    weight = calculateWarmupWeight(uptime, warmup, weight);
+                    weight = calculateWarmupWeight((int)uptime, warmup, weight);
                 }
             }
         }