HBASE-24377 MemStoreFlusher throw NullPointerException (apache#1721)

Signed-off-by: Ramkrishna <ramkrishna@apache.org>
Signed-off-by: Anoop Sam John <anoop.hbase@gmail.com>
Signed-off-by: Duo Zhang <zhangduo@apache.org>
(cherry picked from commit 9b3fe09)

Change-Id: I3cba54b8c53775ccbf7f35c9a85c340af9e09663

hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/MemStoreFlusher.java

@@ -86,8 +86,6 @@ class MemStoreFlusher implements FlushRequester {
   private final FlushHandler[] flushHandlers;
   private List<FlushRequestListener> flushRequestListeners = new ArrayList<>(1);
 
-  private FlushType flushType;
-
   /**
    * Singleton instance inserted into flush queue used for signaling.
    */
@@ -148,17 +146,13 @@ public LongAdder getUpdatesBlockedMsHighWater() {
     return this.updatesBlockedMsHighWater;
   }
 
-  public void setFlushType(FlushType flushType) {
-    this.flushType = flushType;
-  }
-
   /**
    * The memstore across all regions has exceeded the low water mark. Pick
    * one region to flush and flush it synchronously (this is called from the
    * flush thread)
    * @return true if successful
    */
-  private boolean flushOneForGlobalPressure() {
+  private boolean flushOneForGlobalPressure(FlushType flushType) {
     SortedMap<Long, HRegion> regionsBySize = null;
     switch(flushType) {
       case ABOVE_OFFHEAP_HIGHER_MARK:
@@ -348,7 +342,7 @@ public void run() {
               // we still select the regions based on the region's memstore data size.
               // TODO : If we want to decide based on heap over head it can be done without tracking
               // it per region.
-              if (!flushOneForGlobalPressure()) {
+              if (!flushOneForGlobalPressure(type)) {
                 // Wasn't able to flush any region, but we're above low water mark
                 // This is unlikely to happen, but might happen when closing the
                 // entire server - another thread is flushing regions. We'll just
@@ -711,7 +705,6 @@ public void reclaimMemStoreMemory() {
           try {
             flushType = isAboveHighWaterMark();
             while (flushType != FlushType.NORMAL && !server.isStopped()) {
-              server.cacheFlusher.setFlushType(flushType);
               if (!blocked) {
                 startTime = EnvironmentEdgeManager.currentTime();
                 if (!server.getRegionServerAccounting().isOffheap()) {
@@ -769,7 +762,6 @@ public void reclaimMemStoreMemory() {
       } else {
         flushType = isAboveLowWaterMark();
         if (flushType != FlushType.NORMAL) {
-          server.cacheFlusher.setFlushType(flushType);
           wakeupFlushThread();
         }
       }