HBASE-28778 NPE may occur when opening master-status or table.jsp or procedure.jsp while Master is initializing (#6210)

Signed-off-by: Duo Zhang <zhangduo@apache.org>
(cherry picked from commit 6a5757d)

Author: guluo2016

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

@@ -77,7 +77,10 @@ public void doGet(HttpServletRequest request, HttpServletResponse response) thro
   private ServerName getMetaLocationOrNull(HMaster master) {
     RegionStateNode rsn = master.getAssignmentManager().getRegionStates()
       .getRegionStateNode(RegionInfoBuilder.FIRST_META_REGIONINFO);
-    return rsn.isInState(RegionState.State.OPEN) ? rsn.getRegionLocation() : null;
+    if (rsn != null) {
+      return rsn.isInState(RegionState.State.OPEN) ? rsn.getRegionLocation() : null;
+    }
+    return null;
   }
 
   private Map<String, Integer> getFragmentationInfo(HMaster master, Configuration conf)

hbase-server/src/main/resources/hbase-webapps/master/procedures.jsp

@@ -47,8 +47,28 @@
 <%@ page import="org.apache.hadoop.hbase.metrics.Histogram" %>
 <%@ page import="java.util.TreeMap" %>
 <%@ page import="org.apache.hadoop.hbase.metrics.impl.HistogramImpl" %>
+
+<jsp:include page="header.jsp">
+    <jsp:param name="pageTitle" value="${pageTitle}"/>
+</jsp:include>
+
 <%
   HMaster master = (HMaster) getServletContext().getAttribute(HMaster.MASTER);
+  if (!master.isInitialized()) {
+%>
+    <div class="container-fluid content">
+      <div class="row inner_header">
+        <div class="page-header">
+          <h1>Master is initializing</h1>
+        </div>
+      </div>
+      <p><hr><p>
+      <jsp:include page="redirect.jsp" />
+    </div>
+<%  return;
+  } %>
+
+<%
   ProcedureExecutor<MasterProcedureEnv> procExecutor = master.getMasterProcedureExecutor();
   List<Procedure<MasterProcedureEnv>> procedures = procExecutor.getProcedures();
   Collections.sort(procedures, new Comparator<Procedure>() {
@@ -63,9 +83,6 @@
   List<LockedResource> lockedResources = master.getLocks();
   pageContext.setAttribute("pageTitle", "HBase Master Procedures: " + master.getServerName());
 %>
-<jsp:include page="header.jsp">
-    <jsp:param name="pageTitle" value="${pageTitle}"/>
-</jsp:include>
 
 <div class="container-fluid content">
   <div class="row top_header">

hbase-server/src/main/resources/hbase-webapps/regionserver/region.jsp

@@ -33,16 +33,22 @@
   String regionName = request.getParameter("name");
   HRegionServer rs = (HRegionServer) getServletContext().getAttribute(HRegionServer.REGIONSERVER);
   FileSystem fs = rs.getFileSystem();
-
-  HRegion region = rs.getRegion(regionName);
+  HRegion region = null;
+  if (regionName != null) {
+    region = rs.getRegion(regionName);
+  }
   String displayName;
   boolean isReplicaRegion = false;
   if (region != null) {
     displayName = RegionInfoDisplay.getRegionNameAsStringForDisplay(region.getRegionInfo(),
             rs.getConfiguration());
     isReplicaRegion = region.getRegionInfo().getReplicaId() > RegionInfo.DEFAULT_REPLICA_ID;
   } else {
-    displayName = "region {" + regionName + "} is not currently online on this region server";
+    if (regionName != null) {
+      displayName = "region {" + regionName + "} is not currently online on this region server";
+    } else {
+      displayName = "you must specify a region name when accessing this page";
+    }
   }
   pageContext.setAttribute("pageTitle", "HBase RegionServer: " + rs.getServerName());
 %>