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author | Joey Hess <joey@kitenet.net> | 2012-06-04 15:40:11 -0400 |
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committer | Joey Hess <joey@kitenet.net> | 2012-06-04 15:40:11 -0400 |
commit | 0accc932cb88a79829cf0cfb3f27b16b46e33140 (patch) | |
tree | 52623d4a44dbaa8328797c7c0f09dd39d08f8fcf /doc/design/assistant/blog/day_1__inotify.mdwn | |
parent | 9b40cd7461cc7b384f21a428a6b99f33301d67dd (diff) |
update
Diffstat (limited to 'doc/design/assistant/blog/day_1__inotify.mdwn')
-rw-r--r-- | doc/design/assistant/blog/day_1__inotify.mdwn | 57 |
1 files changed, 57 insertions, 0 deletions
diff --git a/doc/design/assistant/blog/day_1__inotify.mdwn b/doc/design/assistant/blog/day_1__inotify.mdwn new file mode 100644 index 000000000..9935698e0 --- /dev/null +++ b/doc/design/assistant/blog/day_1__inotify.mdwn @@ -0,0 +1,57 @@ +First day of [Kickstarter funded work](http://www.kickstarter.com/projects/joeyh/git-annex-assistant-like-dropbox-but-with-your-own/)! + +Worked on [[inotify]] today. The `watch` branch in git now does a pretty +good job of following changes made to the directory, annexing files +as they're added and staging other changes into git. Here's a quick +transcript of it in action: + + joey@gnu:~/tmp>mkdir demo + joey@gnu:~/tmp>cd demo + joey@gnu:~/tmp/demo>git init + Initialized empty Git repository in /home/joey/tmp/demo/.git/ + joey@gnu:~/tmp/demo>git annex init demo + init demo ok + (Recording state in git...) + joey@gnu:~/tmp/demo>git annex watch & + [1] 3284 + watch . (scanning...) (started) + joey@gnu:~/tmp/demo>dd if=/dev/urandom of=bigfile bs=1M count=2 + add ./bigfile 2+0 records in + 2+0 records out + 2097152 bytes (2.1 MB) copied, 0.835976 s, 2.5 MB/s + (checksum...) ok + (Recording state in git...) + joey@gnu:~/tmp/demo>ls -la bigfile + lrwxrwxrwx 1 joey joey 188 Jun 4 15:36 bigfile -> .git/annex/objects/Wx/KQ/SHA256-s2097152--e5ced5836a3f9be782e6da14446794a1d22d9694f5c85f3ad7220b035a4b82ee/SHA256-s2097152--e5ced5836a3f9be782e6da14446794a1d22d9694f5c85f3ad7220b035a4b82ee + joey@gnu:~/tmp/demo>git status -s + A bigfile + joey@gnu:~/tmp/demo>mkdir foo + joey@gnu:~/tmp/demo>mv bigfile foo + "del ./bigfile" + joey@gnu:~/tmp/demo>git status -s + AD bigfile + A foo/bigfile + +Due to Linux's inotify interface, this is suely some of the most subtle, +race-heavy code that I'll need to deal with while developing the git annex +assistant. But I can't start wading, need to jump off the deep end to make +progress! + +The hardest problem today involved the case where a directory is moved +outside of the tree that's being watched. Inotify will still send events +for such directories, but it doesn't make sense to continue to handle them. + +Ideally I'd stop inotify watching such directories, but a lot of state +would need to be maintained to know which inotify handle to stop watching. +(Seems like Haskell's inotify API makes this harder than it needs to be...) + +Instead, I put in a hack that will make it detect inotify events from +directories moved away, and ignore them. This is probably acceptable, +since this is an unusual edge case. + +---- + +The notable omission in the inotify code, which I'll work on next, is +staging deleting of files. This is tricky because adding a file to the +annex happens to cause a deletion event. I need to make sure there are no +races where that deletion event causes data loss. |