HDFS-17339:Skip cacheReport when one blockPool does not have CacheBlock on this DataNode (#6456). Contributed by lei w.

Signed-off-by: Shuyan Zhang <zhangshuyan@apache.org>

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BPServiceActor.java

@@ -503,6 +503,10 @@ DatanodeCommand cacheReport() throws IOException {
 
       String bpid = bpos.getBlockPoolId();
       List<Long> blockIds = dn.getFSDataset().getCacheReport(bpid);
+      // Skip cache report
+      if (blockIds.isEmpty()) {
+        return null;
+      }
       long createTime = monotonicNow();
 
       cmd = bpNamenode.cacheReport(bpRegistration, bpid, blockIds);