The UpdateAttibute processor is used to manipulate NIFI attributes. [1]

In its basic form, you can add attributes from within the properties of the processor. Every FlowFile that goes through the processor will get updated with what you’ve configured in it.

For instance below:

Within the properties of the processor UpdateAttribute I’ve configured him to enrich all FlowFiles that go through it to now contain 2 attributes (MyAttribute1 / MyAttribute2) with their respective values.

I can use those attributes anywhere that accepts regular expression.

It is usually shown when hovering over a question mark within a processor’s property. We can also find out if a processor property accepts regular expression from the Apache NIFI online documentation [2] or from within your NIFI install top right.

Conditional attribute enhancement [IF,IF,…ELSE]

Let’s take a use case in which we are getting data from lots of sources and depending on where they are coming from we are going to do different things with them or set required settings for further upstream processing.

For this example, we are going to get data from EDGE site 1 / EDGE site 2 / EDGE site 3. We will tag all the feeds with an identifier of NIFI.FEED based on a condition and all FlowFiles with an identifier to tell us what NIFI host processed the data and further:

• For EDGE site 1 we want to grab the data, binary merge and further, we are going to send it to Hadoop saving it to directory tree /data/${FEED}/YYYY-MM-dd-hh-mm/${filename}
• For EDGE site 2 we want to enrich so we send it to local disk and change the filename to YYYY-MM-dd-hh-mm-$OriginalFileName-$UUID
• For EDGE site 3 we want to SFTP the data

We can set the framework to route these FlowFile’s based on conditions “IF statements” in the ADVANCED section of our UpdateAttribute.

Like so:

EDGE DEVICE 1

EDGE DEVICE 2

EDGE DEVICE 3

Now the FlowFile’s that route through this UpdateAtrribute processor that meet true for the conditions set on the condition section of the advanced tab, will be enriched with the attributes set on the actions section of the advanced tab on the UpdateAttribute processor.

Note that at the very end if no condition set anything for the parent attribute set on the parent level of the UpdateAttribute it will globally set that attribute, in this case with set NIFI.HOST to ${hostname(true)}

We can then use the RouteOnAttribute processor to make routing decisions, discussed on another blog in the future.

Note also that we have a routing strategy. CLONE or ORIGINAL

CLONE will make duplicate FlowFile’s that meet true for the conditions set.

ORIGINAL will keep one FlowFile iterating through the list of conditions. If the actions set same attributes, the last one wins and so order matters and you can drag your rules around.

Offical advanced documentation found here. [3]