The body of the HDFSBolt.execute() method is essentially one try-catch block. The catch block reports the error and fails the current tuple. In some cases the bolt's FSDataOutputStream object (named 'out') is in an unrecoverable state and no subsequent calls to execute() can succeed.
To produce this scenario:
- process some tuples through HDFS bolt
- put the underlying HDFS system into safemode
- process some more tuples and receive a correct ClosedChannelException
- take the underlying HDFS system out of safemode
- subsequent tuples continue to fail with the same exception
The three fundamental operations that execute takes (writing, sync'ing, rotating) need to be isolated so that errors from each are specifically handled.