During HFile create, at the end when called close() on the OutputStream, there is some pending data to get flushed. When this flush happens, an Exception is thrown back from Storage. The Azure-storage SDK layer will throw back IOE. (Even if it is a StorageException thrown from the Storage, the SDK converts it to IOE.) But at HBase, we end up getting IllegalArgumentException which causes the RS to get aborted. If we get back IOE, the flush will get retried instead of aborting RS.
The reason is this
NativeAzureFsOutputStream uses Azure-storage SDK's BlobOutputStreamInternal. But the BlobOutputStreamInternal is wrapped within a SyncableDataOutputStream which is a FilterOutputStream. During the close op, NativeAzureFsOutputStream calls close on SyncableDataOutputStream and it uses below method from FilterOutputStream
Here the flush call caused an IOE to be thrown to here. The finally will issue close call on ostream (Which is an instance of BlobOutputStreamInternal)
When BlobOutputStreamInternal#close() is been called, if there was any exception already occured on that Stream, it will throw back the same Exception
So here both try and finally block getting Exceptions and Java uses Throwable#addSuppressed()
Within this method if both Exceptions are same objects, it throws back IllegalArgumentException