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| -rw-r--r-- | doc/design/assistant/blog/day_57__afk.mdwn | 40 |
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diff --git a/doc/design/assistant/blog/day_57__afk.mdwn b/doc/design/assistant/blog/day_57__afk.mdwn new file mode 100644 index 000000000..0797c5adb --- /dev/null +++ b/doc/design/assistant/blog/day_57__afk.mdwn @@ -0,0 +1,40 @@ +Probably won't be doing any big coding on the git-annex assistant in the +upcoming week, as I'll be traveling and/or slightly ill enough that I can't +fully get into [flow](http://en.wikipedia.org/wiki/Flow_(psychology)). + +--- + +There was a new Yesod release this week, which required minor changes to +make the webapp build with it. I managed to keep the old version of Yesod +also supported, and plan to keep that working so it can be built with the +version of Yesod available in, eg, Linux distributions. TBD how much pain +that will involve going forward. + +--- + +I'm mulling over how to support stopping/pausing transfers. The problem +is that if the assistant is running a transfer in one thread, and the +webapp is used to cancel it, killing that thread won't necessarily stop the +transfer, because, at least in Haskell's thread model, killing a thread +does not kill processes started by the thread (like rsync). + +So one option is to have the transfer thread run a separate git-annex +process, which will run the actual transfer. And killing that process will +stop the transfer nicely. However, using a separate git-annex process means +a little startup overhead for each file transferred (I don't know if it'd +be enough to matter). Also, there's the problem that git-annex is sometimes +not installed in PATH (wish I understood why cabal does that), which +makes it kind of hard for it to run itself. (It can't simply fork, sadly. +See past horrible pain with forking and threads.) + +The other option is to change the API for git-annex remotes, so that +their `storeKey` and `retrieveKeyFile` methods return a pid of the program +that they run. When they *do* run a program.. not all remotes do. This +seems like it'd make the code in the remotes hairier, and it is also asking +for bugs, when a remote's implementation changes. Or I could go +lower-level, and make every place in the utility libraries that forks a +process record its pid in a per-thread MVar. Still seems to be asking for +bugs. + +Oh well, at least git-annex is already crash-safe, so once I figure out +how to kill a transfer process, I can kill it safely. :) |