Rewrite the SFTP-related plugins under embulk.org

[dmikurube]

The SFTP-related plugins under embulk.org (such as embulk-input-sftp) uses JSch, but it has no longer been maintained since its 0.1.55 in 2018.

http://www.jcraft.com/jsch/ChangeLog

We need to migrate them to some other method for SFTP, but it is expected to be a "total rewrite".

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We are looking for a great contributor for this upgrade, which effectively means that we are looking for a new maintainer for the long-term.

There are several SSH protocol implementations for Java, such as:

• Matthias Wiedemann's JSch fork
• sshj
• Apache Commons VFS
  • ... which uses JSch in it, and they seem to have the same issue.
  • Another Apache project Camel has moved to Matthias Wiedemann's JSch fork, just for reference.

We wanted the (new) long-term maintainer to be a decision maker also on it.

If you're interested in it, please let us know in this Discussion at first.

[dmikurube]

Note on some past investigations.

• JSch's last release was Nov, 2018.
  • https://mvnrepository.com/artifact/com.jcraft/jsch/0.1.55
• It was not released for 2 years before that.
  • https://mvnrepository.com/artifact/com.jcraft/jsch
• We see much less discussions in the official mailing list:
  • https://sourceforge.net/p/jsch/mailman/jsch-users/?viewmonth=201911
• The original author does not seem in response.
  • https://github.com/ymnk
  • https://twitter.com/ymnk/with_replies

Some studies by others:

• https://medium.com/@ldclakmal/comparison-of-commons-vfs-sshj-and-jsch-libraries-for-sftp-support-cd5a0db2fbce (as of Mar, 2017)
• (written in Japanese) https://srad.jp/~coara/journal/614370/

[kakoni]

Also there is MINA https://github.com/apache/mina-sshd

[dmikurube]

Yes, but they internally use (forked) JSch. https://github.com/apache/mina-sshd/blob/sshd-2.13.1/pom.xml#L508