[jira] [Created] (HDFS-13451) Fix Some Potential NPE

["lujie (JIRA)" <ji...@apache.org>]

lujie created HDFS-13451:
----------------------------

             Summary: Fix Some Potential NPE
                 Key: HDFS-13451
                 URL: https://issues.apache.org/jira/browse/HDFS-13451
             Project: Hadoop HDFS
          Issue Type: Bug
            Reporter: lujie


We have developed a static analysis tool [NPEDetector|https://github.com/lujiefsi/NPEDetector] to find some potential NPE. Our analysis shows that some callees may return null in corner case(e.g. node crash , IO exception), some of their callers have  _!=null_ check but some do not have. In this issue we post a patch which can add  !=null  based on existed !=null  check. For example:

callee BlockInfo#getDatanode may return null:
{code:java}
public DatanodeDescriptor getDatanode(int index) {
    DatanodeStorageInfo storage = getStorageInfo(index);
   return storage == null ? null : storage.getDatanodeDescriptor();
}
{code}
it has 4 callers, 3 of them have \!=null checker, like in CacheReplicationMonitor#addNewPendingCached:
{code:java}
DatanodeDescriptor datanode = blockInfo.getDatanode(i);
if (datanode == null) {
   continue;
}
{code}
but in caller NamenodeFsck#blockIdCK have no \!null checker, we add checker just like CacheReplicationMonitor#addNewPendingCached
{code:java}
DatanodeDescriptor dn = blockInfo.getDatanode(idx);
if (dn == null) {
    continue;
}
{code}
But due to we are not very  familiar with CASSANDRA, hope some expert can review it. Thanks!!!!



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