sftp.rename doesn't behave like OpenSSH's rename

[mflage]

I'm not sure if this is a bug or a feature, but when looking at the implementation of the .rename function for the sftp module in Paramiko this doesn't trigger MOVED_FROM and MOVED_TO, instead it triggers CREATE and DELETE events. Is this normal? What is it that paramiko does differently when renaming a file that causes these two events to be created instead of MOVED_FROM and MOVED_TO?

I have tested this with version 2.2.1 of Paramiko. This is the output of 'inotifywait -r -m /tmp/test' which illustrates the difference (the file "test" is uploaded and then renamed to "testfile"):

When using sftp from OpenSSH:

/tmp/test/ CREATE test
/tmp/test/ OPEN test
/tmp/test/ MODIFY test
/tmp/test/ CLOSE_WRITE,CLOSE test
/tmp/test/ MOVED_FROM test
/tmp/test/ MOVED_TO testfile

When using paramiko:

/tmp/test/ CREATE test
/tmp/test/ OPEN test
/tmp/test/ MODIFY test
/tmp/test/ CLOSE_WRITE,CLOSE test
/tmp/test/ CREATE testfile
/tmp/test/ DELETE test

[bitprophet]

Excellent question, I don't know off the top of my head what exact protocol messages the SFTP modules use, but it would not surprise me if their initial implementation was slightly off-spec (or if the spec has changed since 2004-ish).

Don't have time to deep-dive right now but I can say that if we find you're right and Paramiko's not doing quite the right thing, I'd be open to changing it (probably in a backwards incompat release in case anyone's relying on quirks of the current approach.)

Thanks for the report!

[mflage]

Heh! I just found that the method posix_rename, which was recently added, does this correctly :)

[bitprophet]

Sounds like someone already ran into the "oops changing this wouldn't be backwards compat", I guess. Does that basically solve your problem for now? If so I might just mutate this into "replace rename with the behavior of posix_rename in 3.0", assuming the latter behavior is actually the default in OpenSSH.

[mflage]

I'm going to be running a test with the customer the following Tuesday, so I'll let you know 100% then if it works for us. But it looks promising, since the inotify events are now the expected ones.

[mflage]

Hi!

I can confirm that posix_rename behaves correctly (like OpenSSH's sftp implementation does). So you can probably go ahead and close this ticket if you want.

[bitprophet]

Thanks for the update @mflage ! I'll spin off some new action items (ugh, business-speak) from this.