YARN-11701. [Federation] Enhance Federation Cache Clean Conditions. (#6889) Contributed by Shilun Fan.

Reviewed-by: Ayush Saxena <ayushsaxena@apache.org>

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-common/src/main/java/org/apache/hadoop/yarn/server/federation/cache/FederationCaffeineCache.java

@@ -79,7 +79,9 @@ public class FederationCaffeineCache extends FederationCache {
 
   @Override
   public void clearCache() {
-    this.cache.cleanUp();
+    if (this.cache != null) {
+      this.cache.cleanUp();
+    }
     this.cache = null;
   }
 

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-common/src/main/java/org/apache/hadoop/yarn/server/federation/cache/FederationGuavaCache.java

@@ -76,7 +76,9 @@ public class FederationGuavaCache extends FederationCache {
 
   @Override
   public void clearCache() {
-    cache.invalidateAll();
+    if (this.cache != null) {
+      cache.invalidateAll();
+    }
     cache = null;
   }
 

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-common/src/main/java/org/apache/hadoop/yarn/server/federation/cache/FederationJCache.java

@@ -91,7 +91,9 @@ public class FederationJCache extends FederationCache {
 
   @Override
   public void clearCache() {
-    this.cache.clear();
+    if (this.cache != null) {
+      this.cache.clear();
+    }
     this.cache = null;
   }