https://community.cloudera.com/t5/Support-Questions/Problem-with-assigning-values-to-attributes-in-NiFi/m-p/199844#M161876 <A rel="user" href="https://community.cloudera.com/users/76211/wojciechleszczynski.html" nodeid="76211">@Wojtek</A><P>I believe you are misunderstanding how the UpdateAttribute processor functions.</P><P>-</P><P>Each new property you add expects a property name (this becomes name of attribute being created or updated) and a value. The value can be a string or a NiFi Expression Language (EL) statement.</P><P>-</P><P>In your screenshot above you have created EL statements. For example</P><P>Property = bytes<BR />Value = ${bytes}</P><P>What the above will actually do is:</P><P>- The EL statement "${bytes}" tells NiFi to try to locate an NiFi attribute (At no time does the updateAttribute processor read the content of the FlowFile) with a property name of bytes and return its assigned value. That returned value will then be used to change the existing value assigned to the FlowFile attribute "bytes" or create a new FlowFile attribute with property name "bytes" and assign the value to that.</P><P>-</P><P>NiFi searches for NiFi Attributes in the following hierarchy:</P><P>1. NiFi checks all existing attributes assigned already to FlowFile being processed.</P><P>2. NiFi checks all in scope process group variables </P><P>3. NiFi checks the NIFi variable registry file</P><P>4. NiFi checks the NiFi JVM properties</P><P>5. NiFi checks the NIFi user system environment variables.</P><P>-</P><P>Since the attribute "bytes" does not exsit in any of these places you are ending up with no value or empty string values being set on all these new properties.</P><P>-</P><P>Since you are trying to extract values from the content and assign those to FlowFile attributes, you will want to use a different processor. Perhaps ExtractText instead.</P><P>-</P><P>Thank you,</P><P>Matt</P><P>-</P><P>If you found this answer addressed your question, please take a moment to login in and click the "ACCEPT" link.</P> Tue, 18 Sep 2018 19:51:01 GMT MattWho 2018-09-18T19:51:01Z