Q: Where can I find information about upgrading to a new NiFi version? - A: We still need to put together a real upgrade guide; however, in the meantime, there are some notes on upgrading in the System Properties section of the Administrator Guide. These tips have to do with setting up your current NiFi in such a way that will make upgrading easier.
Q: Where can I find information about the REST API? - A: The REST API documentation is included in the "help" documentation within the application and also on our web site here. To get to the documentation within the application, click on the "help" link in the upper-right corner of the NiFi user interface. Then, in the pane on the left-hand side, scroll down to the very bottom, where you will see a Developer section, with links to the Developer Guide and the REST API documentation.
Q: How do I select multiple items on the graph at the same time, such as if I want to select and move a group of processors? - A: You can either select one item, and then hold down the Shift key and select other items, or you can click anywhere on the blank graph, outside what you want to select, then hold down the shift key and drag a selection box around what you want to select.
Q: Am I correct in assuming that I can transit large volumes of data through NiFi flows in and out of Hadoop? Yes, you are correct that large payloads can be moved through NiFi. As data moves through NiFi, a pointer to the data is being passed around, referred to as a FlowFile. The content of the FlowFile is only accessed as needed. The key for large payloads would be to operate on the payload in a streaming fashion so that you don't read too many large payloads into memory and exceed your JVM memory. As an example, a typical pattern for bringing data into HDFS from NiFi, is to use a MergeContent processor right before a PutHDFS processor. MergeContent can take many small/medium size files and merge them together to form an appropriate size file for HDFS. It does this by copying all of the input streams from the original files to a new output stream, and can, therefore, merge a large amount of files without exceeding the memory of the JVM.
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