FlowFile Continuation
Sometimes you need to backup your current running flow, let that flow run at a later date, or make a backup of what is in process now. You want this in a permanent storage and want to reconstitute it later like Orange Juice. And add it back into the flow or restart it.
This could be do to failures, for integration testing, for testing new versions of components, as a checkpoint or for many other purposes. You don't always want to reprocess the original source or files (they may be gone).
Option 1:
You can save that raw data that came in originally in local files or HDFS. Then read it out of there later.
Option 2: Preferred: MergeContent to FlowFileV3 then Reload with Get* to IdentifyMimeType to UnpackContent
Using MergeContent with FlowFileV3 option. After that step you can PutFile, PutS3Object, PutHDFS or other file saving options. Perhaps send it to an FTP or sFTP server for storage elsewhere.
Now you have a pkg file.
cat /opt/demo/flow/904381478117605.pkg
NiFiFF3+tempf73.02sql.args.2.value29.7sql.args.11.type3roll353.9306742667328
mqtt.brokertcp://m13.cloudmqtt.com:14162sql.args.4.type3uuid$9f2f8b6f-2870-40a3-a460-49427cddf9a8
mqtt.topicsensorsql.args.7.type3sql.args.7.value353.9306742667328path./sql.args.4.value33.9sql.args.9.value-0.0sql.args.1.type1humidity29.7pitch14.015266431562901
nf.file.path.mqtt.qos0sql.args.8.type3temp33.9sql.args.1.value34sql.args.2.type3sql.args.10.type3sql.args.8.value128.4983979122009sql.args.5.type3sql.args.6.value14.015266431562901sql.args.3.value1011.1sql.args.10.value-0.0mqtt.isDuplicatefalspressure1011.1mqtt.isRetainedfalseyaw128.4983979122009cputemp3filename904381478117605sql.args.11.value1.0sql.args.9.type3x-0.0y-0.0z1.0sql.args.6.type3
nf.file.name904381478117605sql.args.5.value73.02sql.args.3.type3�[{"tempf": 73.02, "pressure": 1011.1, "pitch": 14.015266431562901, "temp": 33.9, "yaw": 128.4983979122009, "humidity": 29.7, "cputemp": "34", "y": -0.0, "x": -0.0, "z": 1.0, "roll": 353.9306742667328}]%
You can now reload that FlowFileV3 at any time, send it to IdentifyMimeType (so it knows it's a FlowFileV3) and then use UnpackContent to reconstitute into the original flow file. Now you can use it like it never stopped and was sent to disk. Now you have an unlimited queue to store pre or partially processed files. Saving time! You could run really expensive processes once and save the preprocessed items, files or models and reuse everywhere!
Choose: FlowFile Stream, v3
Thanks to Joe Witt for explanation of the process.
Reference:
https://nifi.apache.org/docs/nifi-docs/components/org.apache.nifi.processors.standard.UnpackContent/
https://nifi.apache.org/docs/nifi-docs/components/org.apache.nifi.processors.standard.MergeContent/
