Home > FreeBSD, Technical Miscellany > Troubleshooting Large, Stalling git/ssh Transfers

Troubleshooting Large, Stalling git/ssh Transfers

Why is git/ssh stalling?

While working with the freebsd-ports repo on github in order to track and combine it with an internal remote repo, it was found to apparently stall during a git push to the internal remote repo. Thinking this was likely a fluke in the network or something, the process was re-executed, but exhibited the same behavior. The OS in this case is FreeBSD 10.0-RELEASE-p6.

Troubleshooting

Identifying the problem started by observing the git process in top which was in a “piperd” wait state. An email thread on freebsd-questions@[1] suggested the process was waiting on a read from a pipe. I only needed to identify the process it was waiting for.

Using lsof, according to the same reference, one could identify the offending process by matching the hex value of the pipe file descriptor to the piped process, in this case ssh. Attaching truss to ssh showed that it had apparently stalled on a getsockopt() operation.

A web search turned up related results[2] (found in References below) which indicated the likely problem was a bug in OpenSSH related to TcpRcvBufPoll. Explicitly disabling this in sshd_config and restarting the service did appear to work around the problem. Upon re-execution of my git push, the process didn’t stall and completed successfully.

Oddly enough, after working around this, I was unable to duplicate the behavior on the same host later. Therefore, there is some doubt that this was indeed the problem, but I post this anyway as it did appear to successfully work around it.

References

[1] FreeBSD Mailing List Archives
[2] stackoverflow post

Disclaimer

Data and information described on this blog are for informational purposes only. The author of this blog provides no warranty/guarantee, expressed or implied, that this data and information will function as described here. Readers are expected to exercise due diligence when researching, developing, and deploying techniques and methods for use within their environments.

Comments posted are the explicit opinions of the comment poster themselves and does not necessarily reflect the views and opinions of the author of this blog.

About these ads
  1. No comments yet.
  1. July 19, 2014 at 1:01 PM

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

Follow

Get every new post delivered to your Inbox.

Join 257 other followers

%d bloggers like this: