Hello everybody,
I have released (Apache License) my NiFi processors at:
https://github.com/uwegeercken/nifi_processors[https://deref-web-02.de/mail/client/WDRw2DECNaw/dereferrer/?redirectUrl=https%3A%2F%2Fgithub.com%2Fuwegeercken%2Fnifi_processors]
Further below is a summary for the processors. I would like to invite everybody
to test, look at the source code and send me any feedback that you have.
I have done a lot of testing but have not been able e.g. to test it in a
cluster setup or with very large amounts of data. Also I am german native
speaking - maybe some of the wording in the processors or documentation could
be enhanced.
Nifi rocks!
Uwe
==========================
Description of processors:
1.
The SplitToAttribute processor for Apache Nifi will allow to split the incoming
content (CSV) of a flowfile into separate fields using a defined separator.
The values of the individual fields will be assigned to flowfile attributes.
Each attribute is named using the defined field prefix plus the positional
number of the field.
A number format can optionally be specified to format the column number. The
number format needs to be according to the Java DecimalFormat class.
Example:
A flow file with following content:
Peterson, Jenny, New York, USA
When the field prefix is set to "column_" and the field number format is set to
"000" the result will be 4 attributes:
column_000 = Peterson column_001 = Jenny column_002 = New York column_003 = USA
Note that this processor can be used together with the MergeTemplate processor,
which merges the flow file attributes with Apache Velocity templates.
2.
The MergeTemplate processor for Apache Nifi will allow to merge the attributes
from a flowfile with an Apache Velocity template. The Velocity template
contains placeholders (e.g. $column0 - alternatively in brackets: ${column0}).
In the merge process the attributes of the flowfile will be merged with the
template and the placeholders are replaced with the attribute values.
See the Apache Velocity website at
http://velocity.apache.org[https://deref-web-02.de/mail/client/mHBrImoMhLc/dereferrer/?redirectUrl=http%3A%2F%2Fvelocity.apache.org]
for details on the template engine.
A filter (regular expression) has to be specified, defining which attributes
shall be considered for the template engine.
The original file will be routed to the "original" relation and the result of
the merge process will replace the content of the flowfile and is routed to the
"merged" relationship.
Example:
A flow file with following attributes:
column0 = Peterson column1 = Jenny column2 = New York column3 = USA
A template file "names.vm" with below format. Placeholders start with a dollar
sign and are optionally in curly brackets:
{ "name": "$column0", "first": "$column1", "city": "$column2", "country":
"$column3" }
After the attributes are merged with the template, the placeholders in the
template are replaced with the values from the flowfile attributes. This is the
result:
{ "name": "Peterson", "first": "Jenny", "city": "New York", "country": "USA" }
Can be used for any textual data formats such as CSV, HTML, XML, Json, etc.
3.
The ExecuteRuleEngine processor allows to process rows of data from CSV files.
It runs business rules against the data and then updates the flowfile
attributes based on the results of the ruleengine. One can then route the
flowfile based on these attributes.
The processor requires to set the ruleengine project zip file and a separator.
The project zip file can be created with the Business Rules Maintenance Tool -
a web application to construct and orchestrate business logic (business rules).
The projects from the web app can be exported and used with the RuleEngine
processor. When the ruleengine runs, it splits the incomming row of data (the
flowfile content) into individual fields. So the separator defines how the
fields are separated from each other.
The advantage of using this processor and a ruleengine is that the business
logic can be defined outside of Nifi. And thus if the logic changes, the flow
does NOT have to be changed. The ruleengine can be used to define complex
business logic. E.g. "Lastname must be XXX and age must be greater than 25 and
country must be Germany or France". This would be difficult to model in nifi
and would clutter the flow. Managed in the web app the business logic can
modified in an agile way and the flow in Nifi stays clean and lean.
Note that there is a test project file: nifi_test2_dev.zip and it can be used
with the test data file: allCountries_100.txt. If you use these files, you
won't need to install/use the Business Rules Maintenance Tool web application.
4.
The GenerateData processor generates random data from word lists, regular
expressions or purely random. The output is in CSV format. This is useful if
you want to generate mass data, but mass data which makes sense (from wordlists
e.g.). Also there are some nice features for generating dependent date columns.
