threads / discuss / 19932

Move JGit off JSch?

Subject: Move JGit off JSch?

## tl;dr

3 messages between Jun 25, 2009 and Jun 25, 2009.

replies: 2people: 3as markdown or json

Shawn O. Pearce· Jun 25, 2009, 18:14 UTC · lore

I'm fed up with JSch.

The remote.<name>.timeout stuff I added recently to JGit causes JSch to throw NPE on timeout[1] and the original author seems to think that's a reasonable thing to do[2].

MINA SSHD[3] contains a different client implementation, licensed under the Apache License 2.0. Its currently missing public key support[4] but the library is actually a pretty solid library, and the author seems to have a decent clue.

I'm really starting to consider adding the public key support the client side of MINA SSHD, and then rewriting TransportGitSsh to use it instead of JSch. The downside is, that really increases our dependency chain, and SSH key management under Eclipse becomes a unique EGit problem as we can't piggy-back onto the existing JSch key management already done by the workbench.

But, I just spent the last ~3 hours digging around JSch trying to fix this NPE bug... and realized the code is very thread unsafe, uses at least 2 threads per connection (your thread, and a thread it spawns for you) so you have no choice but to use threads, and the author seems to think random NPEs are OK (see [2] and all of the NPE bugs on sourceforge).

[1] http://jira.source.android.com/jira/browse/GERRIT-233 [2] http://www.mail-archive.com/jsch-users@lists.sourceforge.net/msg00520.html [3] http://mina.apache.org/sshd/ [4] https://issues.apache.org/jira/browse/SSHD-25

-- 
Shawn.

Ferry Huberts· Jun 25, 2009, 20:52 UTC · re: Shawn O. Pearce · lore

Re: Move JGit off JSch?

Shawn O. Pearce wrote:

> I'm fed up with JSch.

Good to know!

Last year I moved our application away from j2ssh to jsch because j2ssh was pratically dead and rather oddly implemented within our application. I chose jsch because Eclipse was using it and development was actually being done on it. I wasn't aware of the issues with it though and also was not aware of MINA. I'll start looking into MINA soon because we're having some rather odd issue in our application that seem to point to problems with jsch under heavy load/many parallel connections. Your story lit up a light in my head to that effect :-)

Are the Eclipse folks aware of these issues? they seem rather serious. Wouldn't it be more effective to try to improve jsch through the eclipse foundation/community, from multiple sides? (excuse me for asking the obvious)

My background is in massive parallel systems so I know about the pain of implementing this kind of thing correctly (and also the reward of seeing it working...)

Robin Rosenberg· Jun 25, 2009, 21:11 UTC · re: Shawn O. Pearce · lore

Re: Move JGit off JSch?

torsdag 25 juni 2009 20:14:28 skrev "Shawn O. Pearce" <spearce@spearce.org>:

Show 10 quoted lines

> I'm fed up with JSch.
> 
> The remote.<name>.timeout stuff I added recently to JGit causes
> JSch to throw NPE on timeout[1] and the original author seems to
> think that's a reasonable thing to do[2].
> 
> MINA SSHD[3] contains a different client implementation, licensed
> under the Apache License 2.0.  Its currently missing public key
> support[4] but the library is actually a pretty solid library,
> and the author seems to have a decent clue.

Clues are useful :)

Show 6 quoted lines

> I'm really starting to consider adding the public key support the
> client side of MINA SSHD, and then rewriting TransportGitSsh to use
> it instead of JSch.  The downside is, that really increases our
> dependency chain, and SSH key management under Eclipse becomes a
> unique EGit problem as we can't piggy-back onto the existing JSch
> key management already done by the workbench.

I haven't really looked into JSch internals, but rewriting complex code without trying hard to fix the problem might not be worth it. New code /will/ have problems and having a different mechanism for key management is in some very obscure corner on the reverse side of my wish list.

> But, I just spent the last ~3 hours digging around JSch trying to

I'm not quite as efficient as you, but I've spent more than three hours on fixing much simpler things.

Show 5 quoted lines

> fix this NPE bug... and realized the code is very thread unsafe,
> uses at least 2 threads per connection (your thread, and a thread
> it spawns for you) so you have no choice but to use threads, and
> the author seems to think random NPEs are OK (see [2] and all of
> the NPE bugs on sourceforge).

Can't we bug him a little more, but then again patches are probably more convincing than bug reports. Perhaps you could explain the issues in more detail before we start rewriting the key management into SSHD.

Should we raise a bug report in eclipse about replacing JSch, in order to get some feedback from Eclipse people?

-- robin