HDFS-17309. RBF: Fix Router Safemode check condition error (#6390) Contributed by liuguanghua.

Reviewed-by: Inigo Goiri <inigoiri@apache.org>
Reviewed-by: Simbarashe Dzinamarira <sdzinamarira@linkedin.com>
Signed-off-by: Shilun Fan <slfan1989@apache.org>

hadoop-hdfs-project/hadoop-hdfs-rbf/src/main/java/org/apache/hadoop/hdfs/server/federation/router/RouterSafemodeService.java

@@ -169,7 +169,7 @@ public class RouterSafemodeService extends PeriodicService {
     }
     StateStoreService stateStore = router.getStateStore();
     long cacheUpdateTime = stateStore.getCacheUpdateTime();
-    boolean isCacheStale = (now - cacheUpdateTime) > this.staleInterval;
+    boolean isCacheStale = (cacheUpdateTime == 0) || (now - cacheUpdateTime) > this.staleInterval;
 
     // Always update to indicate our cache was updated
     if (isCacheStale) {

hadoop-hdfs-project/hadoop-hdfs-rbf/src/main/java/org/apache/hadoop/hdfs/server/federation/store/StateStoreService.java

@@ -132,6 +132,8 @@ public class StateStoreService extends CompositeService {
     // Caches to maintain
     this.cachesToUpdateInternal = new ArrayList<>();
     this.cachesToUpdateExternal = new ArrayList<>();
+
+    this.cacheLastUpdateTime = 0;
   }
 
   /**