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From Paul Chavez <pcha...@verticalsearchworks.com>
Subject RE: best way to put UDP JSON data into Hadoop
Date Thu, 30 May 2013 20:43:12 GMT
I can't speak to the UDP transport mechanism, but we do use JSON events with Hive and it works
quite well. 

In our case we have an application that takes an internal object, serializes it to JSON, puts
that JSON into another object we call the 'flume envelope' which has timestamp and a couple
other headers for routing. We use an HTTPSource to POST the JSON 'envelope' events to flume,
which never does anything special with the JSON 'payload'. On the sink side, after a couple
Avro hops we serialize to TEXT files with the HDFS sink. Then we use a Hive JSON SerDe to
create an external table (flume is configured to write to partitions based on the timestamp).
Every hour an Oozie job processes the previous hour data into a 'native' Hive table and then
we drop the external partition and data. The only catch is the JSON events have to be on a
single line. 

This overall workflow has proven to be extremely useful and flexible. We manage multiple data
flows with a single source/channel/sink by writing to paths based on the envelope headers.
(eg /flume/%{logType}/%{logSubType}/date=%Y%M%d/hour=%H)

Hope that helps!
Paul Chavez

-----Original Message-----
From: Peter Eisentraut [mailto:peter@eisentraut.org] 
Sent: Thursday, May 30, 2013 1:27 PM
To: user@flume.apache.org
Subject: best way to put UDP JSON data into Hadoop

I have a use case for Flume and I'm wondering which of the many options in Flume to use for
making this work.

I have a data source that produces log data in UDP packets containing JSON (a bit like syslog,
but the data is already structured).  I want to get this into Hadoop somehow (either HBase
or HDFS+Hive, not sure yet).

My first attempt was to write a sink (based on the syslog UDP sink) that receives UDP packets,
parses the JSON, stuffs the fields into the headers of the internal Flume event object, and
sends it off.  (The body is left empty.)  On the receiving end, I wrote a serializer for the
hbase sink that writes each header field into a separate column.  That works, but I was confused
that the default supplied hbase serializers ignored all event headers, so I was wondering
whether I'm abusing them.

An alternative approach I was thinking about was writing a generic UDP sink that stuffs the
entire UDP packet into the event body, and then write a serializer for the hbase sink that
parses the JSON and puts the fields into the columns.  Or alternatively write the JSON straight
into HDFS and have Hive to the JSON parsing later.

Which one of these would be more idiomatic and/or generally useful?

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