Index: src/java/org/apache/hadoop/hbase/HRegionServer.java =================================================================== --- src/java/org/apache/hadoop/hbase/HRegionServer.java (revision 647934) +++ src/java/org/apache/hadoop/hbase/HRegionServer.java (working copy) @@ -1475,6 +1475,19 @@ final long timestamp, final RowFilterInterface filter) throws IOException { checkOpen(); + NullPointerException npe = null; + if (regionName == null) { + npe = new NullPointerException("regionName is null"); + } else if (cols == null) { + npe = new NullPointerException("columns to scan is null"); + } else if (firstRow == null) { + npe = new NullPointerException("firstRow for scanner is null"); + } + if (npe != null) { + IOException io = new IOException("Invalid arguments to openScanner"); + io.initCause(npe); + throw io; + } requestCount.incrementAndGet(); try { HRegion r = getRegion(regionName);