Hi Yogi, Here is an example I wrote. https://github.com/tweise/apex-samples/pulls
In the above example, the file is finalized when there are no more tuples received in the window. Finalization of file happens when the file is rotated (based on size/time). However for example or demo purpose, we can finalize a file if there aren't any input tuples received in a window. If there are more tuples after some time, they need to be written to a different file. Maybe this can be controlled by a property? Let me know if you want me to put this in Malhar. Thanks, Chandni On Thu, Mar 3, 2016 at 5:51 PM, Yogi Devendra <[email protected]> wrote: > Any suggestions/ comments on this? > > ~ Yogi > > On 3 March 2016 at 17:44, Yogi Devendra <[email protected]> wrote: > > > Hi, > > > > Currently, for writing to HDFS file we have AbstractFileOutputOperator in > > the malhar library. > > > > It has following abstract methods : > > 1. protected abstract String getFileName(INPUT tuple) > > 2. protected abstract byte[] getBytesForTuple(INPUT tuple) > > > > These methods are kept generic to give flexibility to the app developers. > > But, someone who is new to apex; would look for ready-made implementation > > instead of extending Abstract implementation. > > > > Thus, I am proposing to add concrete operator HDFSOutputOperator to > > malhar. Aim of this operator would be to serve the purpose of ready to > use > > operator for most frequent use-cases. > > > > Here are my key observations on most frequent use-cases: > > > > > ------------------------------------------------------------------------------ > > > > 1. Writing tuples of type byte[] or String. > > 2. All tuples on a particular stream land up in the same output file. > > 3. App developer may want to add some custom tuple separator (e.g. > newline > > character) between tuples. > > > > Please mention your comments regarding : > > -------------------------------------------------------- > > > > 1. Will it be useful to have such concrete operator? > > > > 2. Do you think of any other datatype other than byte[], String that > > should be supported out of the box by this concrete operator? > > Currently, I am planning to include byte[], String, any other type having > > valid toString() as input tuples. > > > > 3. Do you think tuple separator should be configurable? > > > > 4. Any other feedback? > > > > > > Proposed design: > > ---------------------- > > > > 1. This concrete implementation will be extending > > AbstractFileOutputOperator with default implementation for abstract > methods > > mentioned above. > > > > 2. Filename , Tuple separator will be exposed as a operator property. > > > > 3. All incoming tuples will be written to same file mentioned in the > > property. > > > > 4. This operator will be added to malhar library under package > > com.datatorrent.lib.io.fs where AbstractFileOutputOperator resides. > > > > ~ Yogi > > >
