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From: Molnár Bálint
Sent: Thursday, March 05, 2015 4:53 AM
To: user@hadoop.apache.org
Subject: HDFS Append Problem
Hi Everyone!
I 'm experiencing an annoying problem.
My Scenario is:
I want to store lots of small files (1-2MB max) in map files. These files will
come periodically during the days, so I cannot use the "factory" writer because
it will create a lot of small MapFiles. (I want to store these files in the
HDFS immediately.)
I' m trying to create a code to append Map files. I use the
org.apache.hadoop.fs.FileSystem append() method which calls the
org.apache.hadoop.hdfs.DistributedFileSystem append() method to do the job.
My code works well, because the stock MapFile Reader can retrieve the files. My
problem appears in the upload phase. When I try to upload a set (1GB) of small
files, the free space of the HDFS decreases fast. The program only uploads
400MB but according to the Cloudera Manager it is more than 5GB.
The interesting part is that, when I terminate the upload, and wait 1-2
minutes, the HDFS goes back to normal size (500MB), and none of my files are
lost. If I don't terminate the upload, the HDFS goes out of free space and the
program gets errors.
I'm using cloudera quickvm 5.3 for testing, and the hdfs replication number is
1.
Any ideas how to solve this issue?
Thanks