SFTP file system in hadoop - hadoop

Question

Does hadoop version 2.0.0 and CDH4 have a SFTP file system in place ? I know hadoop has a support for FTP Filesystem . Does it have something similar for sftp ? I have seen some patches submitted for the sme though couldn't make sense of them ..

Answer 1

Consider using hadoop distcp.
Check here. That would be something like:
hadoop distcp
-D fs.sftp.credfile=/user/john/credstore/private/mycreds.prop
sftp://myHost.ibm.com/home/biadmin/myFile/part1
hdfs:///user/john/myfiles

Answer 2

After some research , I have figured out that hadoop currently doesn't have a FileSystem written for SFTP . Hence if you wish to read data using SFTP channel you have to either write a SFTP FileSystem (which is quite a big deal , extending and overriding lots of classes and methods) , patches of which are already been developed , though not yet integrated into hadoop , else get a customized InputFormat that reads from streams , which again is not implemented in hadoop.

Answer 3

You need to ensure core-site.xml is having property fs.sftp.impl set with value org.apache.hadoop.fs.sftp.SFTPFileSystem
Post this hadoop commands will work. Couple of samples are given below
ls command
Command on hadoop
hadoop fs -ls /
equivalent for SFTP
hadoop fs -D fs.sftp.user.{hostname}={username} -D fs.sftp.password.{hostname}.{username}={password} -ls sftp://{hostname}:22/
Distcp command
Command on hadoop
hadoop distcp {sourceLocation} {destinationLocation}
equivalent for SFTP
hadoop distcp -D fs.sftp.user.{hostname}={username} -D fs.sftp.password.{hostname}.{username}={password} sftp://{hostname}:22/{sourceLocation} {destinationLocation}
Ensure you are replacing all the place holders while trying these commands. I tried them on AWS EMR 5.28.1 which has Hadoop 2.8.5 installed on it

Answer 4

So hopefully cleaning up these answers a bit into something more digestible. Basically Hadoop/HDFS is capable of support SFTP, it's just not enabled by default, nor is it really documented in the core-default.xml very well.
The key configuration you need to set to enable SFTP support is:
<property>
<name>fs.sftp.impl</name>
<value>org.apache.hadoop.fs.sftp.SFTPFileSystem</value>
</property>
Alternatively, you can set it right at the CLI depending on your command
hdfs dfs \
-Dfs.sftp.impl=org.apache.hadoop.fs.sftp.SFTPFileSystem \
-Dfs.sftp.keyfile=~/.ssh/java_sftp_testkey.ppk \
-ls sftp://$USER#localhost/tmp/
The biggest requirement is that your SSH Keyfile needs to be password-less to work. This can be done via
cp ~/.ssh/mykeyfile.ppk ~/.ssh/mykeyfile.ppk.orig
ssh-keygen -p -P MyPass -N "" -f ~/.ssh/mykeyfile.ppk
mv ~/.ssh/mykeyfile.ppk ~/.ssh/mykeyfile_nopass.ppk
mv ~/.ssh/mykeyfile.ppk.orig ~/.ssh/mykeyfile.ppk
And finally, the biggest (and maybe neatest) is using this via distcp, if you need to send/receive a large amount of data to/from an SFTP server. There's an oddity about the ssh keyfile being needed locally to generate the directory listing, as well as on the cluster for the actual workers.
Something like this should work well enough:
cd workdir
ln -s ~/.ssh/java_sftp_testkey.ppk
hadoop distcp \
--files ~/.ssh/java_sftp_testkey.ppk \
-Dfs.sftp.impl=org.apache.hadoop.fs.sftp.SFTPFileSystem \
-Dfs.sftp.keyfile=java_sftp_testkey.ppk \
hdfs:///path/to/source/ \
sftp://user#FQDN/path/to/dest