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From Jagadish Bihani <jagadish.bih...@pubmatic.com>
Subject HDFS file rolling behaviour
Date Tue, 18 Sep 2012 12:08:38 GMT
Hi

Does anybody know about  the issue mentioned in the following mail?


Update: I have seen following behaviour now even for time based rolling.
By time based rolling I would expect: That single file should be created 
after x seconds.
But in my case some n files are created after every x seconds.
Is it something to do with HDFS batch size?

Regards,
Jagadish


-------- Original Message --------
Subject: 	HDFS file rolling behaviour
Date: 	Thu, 13 Sep 2012 14:26:56 +0530
From: 	Jagadish Bihani <jagadish.bihani@pubmatic.com>
To: 	user@flume.apache.org



Hi

I use two flume agents:
1. flume_agent 1 which is a source with (exec source -file channel -avro 
sink)
2. flume_agent 2 which is a dest with (avro source -file channel - HDFS 
sink)

I have observed that for HDFS sink with rolling by *file size/number of 
events* it
creates a lot of simultaneous connections to source's avro sink. But
while rolling by *time interval* it does it *one by one* i.e. opens 1 
HDFS file write to
it and then close it.  I expect for other rolling intervals too same 
thing should happen
i.e.  first open file and if x number of events are written to it then 
roll it and open another
and so on.

In my case my data ingestion works fine with "time" based rolling but in 
other
cases due to the above behaviour I get exceptions like:
-- too many open files
-- timeout related exceptions for file channel and few more exceptions.

I can increase the values of the parameters giving exceptions but I dont 
know what
adverse effects it may have.

Can somebody throw some light on the rolling based on file size/number 
of events ?

Regards,
Jagadish




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