HBASE-27951 Use ADMIN_QOS in MasterRpcServices for regionserver opera…

…tional dependencies (#5309)

It seems not correct to have the MasterRpcServices methods for direct
regionserver<->master communication (regionServerStartup, regionServerReport,
and reportFatalRSError) contending with normal priority requests. They
should be made ADMIN_QOS priority to avoid potential operational deadlocks.

Signed-off-by: Duo Zhang <zhangduo@apache.org>
Signed-off-by: Viraj Jasani <vjasani@apache.org>
Reviewed-by: Aman Poonia <aman.poonia.29@gmail.com>

hbase-server/src/main/java/org/apache/hadoop/hbase/master/MasterRpcServices.java

@@ -618,6 +618,7 @@ public GetLastFlushedSequenceIdResponse getLastFlushedSequenceId(RpcController c
   }
 
   @Override
+  @QosPriority(priority = HConstants.ADMIN_QOS)
   public RegionServerReportResponse regionServerReport(RpcController controller,
     RegionServerReportRequest request) throws ServiceException {
     try {
@@ -653,6 +654,7 @@ public RegionServerReportResponse regionServerReport(RpcController controller,
   }
 
   @Override
+  @QosPriority(priority = HConstants.ADMIN_QOS)
   public RegionServerStartupResponse regionServerStartup(RpcController controller,
     RegionServerStartupRequest request) throws ServiceException {
     // Register with server manager
@@ -684,6 +686,7 @@ public RegionServerStartupResponse regionServerStartup(RpcController controller,
   }
 
   @Override
+  @QosPriority(priority = HConstants.ADMIN_QOS)
   public ReportRSFatalErrorResponse reportRSFatalError(RpcController controller,
     ReportRSFatalErrorRequest request) throws ServiceException {
     String errorText = request.getErrorMessage();