Hello Ravi,

You might consider using DistCh.  In the same way that DistCp is a distributed copy implemented as a MapReduce job, DistCh is a MapReduce job that distributes the work of chmod/chown.

DistCh will become easier to access through convenient shell commands in Apache Hadoop 3.  In version 2.6.0, it's undocumented and hard to find, but it's still there.  It's inside the hadoop-extras.jar.  Here is an example invocation:

hadoop jar share/hadoop/tools/lib/hadoop-extras-*.jar org.apache.hadoop.tools.DistCh

It might take some fiddling with the classpath to get this right.  If so, then I recommend looking at how the shell scripts in trunk set up the classpath.

https://github.com/apache/hadoop/blob/trunk/hadoop-tools/hadoop-extras/src/main/shellprofile.d/hadoop-extras.sh

As you pointed out, this would generate higher NameNode traffic compared to your typical baseline load.  To mitigate this, I recommend that you start with a test run in a non-production environment to see how it reacts.
From: ravi teja <[EMAIL PROTECTED]<mailto:[EMAIL PROTECTED]>>
Date: Wednesday, June 15, 2016 at 8:33 PM
To: "[EMAIL PROTECTED]<mailto:[EMAIL PROTECTED]>" <[EMAIL PROTECTED]<mailto:[EMAIL PROTECTED]>>
Subject: Bulk chmod,chown operations on HDFS

Hi Community,

As part of the new authorisation changes, we need to change the permissions and owners of many files in hdfs (2.6.0) with chmod and chown.

To do this we need to stop the processing on the directories to avoid inconsistencies in permissions, hence we need to take a downtime for those specific pipelines operating on these folders.
The total number of files/directories to be operated upon is around 10 Million.
A chmod recursive (chmod -R) on 160K objects, has taken around 15 minutes.

At this rate it will take a long time to complete the operation and the downtime would be couple of hours.

Mapreduce program  is one option, but chmod,chown being a heavy operations, will slow down the cluster for other users, if done at this scale.

Are there any options to do a bulk permissions changes chmod,chown to avoid these issues?
If not are there any alternative approaches to carry the same operation at this scale something like admin backdoor to fsimage?

Thanks,
Ravi Teja

 
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