ssh control master
Posted on 17 March 2006
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Made one useful bit of progress in the ssh control master stuff.
Before, I was having trouble with getting the control master running and out of the way. I didn't really know how to launch stuff in the background, so I basically forked the thing and polled the control master every 3 seconds to see if it was connected or not. But that was a really fragile setup, and sometimes, if I didn't type my password fast enough, I wouldn't be able to get a connection.
Tonight I have found a much simpler way to get the CM running: I just use the -f flag to make it go to background right before running the command, that is, only after it has completed the connection. This way, I don't need wait around polling, to see if the CM is running. This is terribly embarrasing how much mysterious all this process stuff is to -- seems shameful to call myself a computer scientist and not at least have some basic notions of how operating systems work. I built a toy OS for school once, but that was a really long time ago. Anyway, it does seem to work. All I know is that the exec function is a piece of darcs-internal code that makes some FFI call to a thing called smart_wait. And I guess smart_wait is happy to return if the thing goes to background or something like that.
Anyway, I was scratching my head for a while as to why I could get darcs put to work, but not darcs get. Turns out that the -S flag to scp means something else than it does for ssh. But no fear, we can use -o ControlMaster instead. Ooh tired. Will have to save this for tomorrow. Something to look forward to. Killing this project at last.
