Added check for tablets with errors, when looking for volume replacements. (apache#4287)

Added check for tablets with errors, when looking for volume replacements.

fixes apache#4234

Author: ArbaazKhan1

server/manager/src/main/java/org/apache/accumulo/manager/TabletGroupWatcher.java

@@ -353,6 +353,7 @@ private static class TableMgmtStats {
     int[] counts = new int[TabletState.values().length];
     private int totalUnloaded;
     private long totalVolumeReplacements;
+    private int tabletsWithErrors;
   }
 
   private TableMgmtStats manageTablets(Iterator<TabletManagement> iter,
@@ -398,6 +399,7 @@ private TableMgmtStats manageTablets(Iterator<TabletManagement> iter,
             "Error on TabletServer trying to get Tablet management information for extent: {}. Error message: {}",
             tm.getExtent(), mtiError);
         this.metrics.incrementTabletGroupWatcherError(this.store.getLevel());
+        tableMgmtStats.tabletsWithErrors++;
         continue;
       }
 
@@ -670,7 +672,17 @@ public void run() {
 
         iter = store.iterator(tableMgmtParams);
         var tabletMgmtStats = manageTablets(iter, tableMgmtParams, currentTServers, true);
-        lookForTabletsNeedingVolReplacement = tabletMgmtStats.totalVolumeReplacements != 0;
+
+        // If currently looking for volume replacements, determine if the next round needs to look.
+        if (lookForTabletsNeedingVolReplacement) {
+          // Continue to look for tablets needing volume replacement if there was an error
+          // processing tablets in the call to manageTablets() or if we are still performing volume
+          // replacement. We only want to stop looking for tablets that need volume replacement when
+          // we have successfully processed all tablet metadata and no more volume replacements are
+          // being performed.
+          lookForTabletsNeedingVolReplacement = tabletMgmtStats.totalVolumeReplacements != 0
+              || tabletMgmtStats.tabletsWithErrors != 0;
+        }
 
         // provide stats after flushing changes to avoid race conditions w/ delete table
         stats.end(managerState);