HBASE-23155 May NPE when concurrent AsyncNonMetaRegionLocator#updateCachedLocationOnError (#718)

Author: infraio

hbase-client/src/main/java/org/apache/hadoop/hbase/client/AsyncNonMetaRegionLocator.java

@@ -570,6 +570,9 @@ private void removeLocationFromCache(HRegionLocation loc) {
     byte[] startKey = loc.getRegion().getStartKey();
     for (;;) {
       RegionLocations oldLocs = tableCache.cache.get(startKey);
+      if (oldLocs == null) {
+        return;
+      }
       HRegionLocation oldLoc = oldLocs.getRegionLocation(loc.getRegion().getReplicaId());
       if (!canUpdateOnError(loc, oldLoc)) {
         return;

hbase-server/src/test/java/org/apache/hadoop/hbase/client/TestAsyncNonMetaRegionLocator.java

@@ -399,4 +399,14 @@ public void testLocateBeforeInOnlyRegion() throws IOException, InterruptedExcept
     assertArrayEquals(loc.getRegion().getStartKey(), EMPTY_START_ROW);
     assertArrayEquals(loc.getRegion().getEndKey(), EMPTY_END_ROW);
   }
+
+  @Test
+  public void testConcurrentUpdateCachedLocationOnError() throws Exception {
+    createSingleRegionTable();
+    HRegionLocation loc =
+        getDefaultRegionLocation(TABLE_NAME, EMPTY_START_ROW, RegionLocateType.CURRENT, false)
+            .get();
+    IntStream.range(0, 100).parallel()
+        .forEach(i -> LOCATOR.updateCachedLocationOnError(loc, new NotServingRegionException()));
+  }
 }