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anoia.svc allow open of a service that is not yet running

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we change the inotify watcher so that it attempts to monitor
/run/service as well as /run/service/foo. If foo doesn't yet exist
then that call to addwatch fails, so we need to be looking at the
parent if we are to be told when foo gets created
This commit is contained in:
Daniel Barlow 2025-03-25 23:37:58 +00:00
parent 7ce1c6bb7d
commit 05991225de
1 changed files with 47 additions and 13 deletions
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60
pkgs/anoia/svc.fnl
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@ -1,22 +1,56 @@
(local inotify (require :inotify))
(local { : file-exists? : dirname : append-path } (require :anoia))
(local { : file-type : dir : mktree &as fs } (require :anoia.fs))
(local { : readlink } (require :lualinux))
(fn read-line [name]
(with-open [f (assert (io.open name :r) (.. "can't open file " name))]
(f:read "*l")))
;; If the directory is missing, we cannot add a inotify watch
;; for it. We need a watch that opens the parent if the pathname is missing,
;; and it needs to be the resolved path not the syntactic parent.
;; If the directory is not missing, then having a watch on the
;; parent may result in extra wakeups but should only affect
;; efficiency not correctness
;; Each time the directory may have been added we need to update
;; watches. If it's been removed, the watch will be removed
;; automatically. inotify_add_watch when it already exists will modify
;; instead of making a new one, so we can treat it as idempotent
(fn resolve-link [pathname]
(if (= (file-type pathname) :link)
(readlink pathname)
pathname))
(fn watch-fsevents [directory-name]
(let [handle (inotify.init)]
(handle:addwatch directory-name
inotify.IN_CREATE
inotify.IN_MOVE
inotify.IN_DELETE
inotify.IN_DELETE_SELF
inotify.IN_MOVED_FROM
inotify.IN_MOVED_TO
inotify.IN_CLOSE_WRITE)
handle))
(let [handle (inotify.init)
parent-name (dirname (resolve-link directory-name))
refresh (fn []
(handle:addwatch directory-name
inotify.IN_CREATE
inotify.IN_MOVE
inotify.IN_DELETE
inotify.IN_DELETE_SELF
inotify.IN_MOVED_FROM
inotify.IN_MOVED_TO
inotify.IN_CLOSE_WRITE)
(handle:addwatch parent-name
inotify.IN_CREATE
inotify.IN_DELETE))]
;; if you are using poll() to check for events on this
;; watcher and on other events at the same time, be sure
;; to call fileno each time around the loop instead
;; of only once
{
:fileno #(do (refresh) (handle:fileno))
:wait #(do (refresh) (handle:read))
:close #(handle:close)
}))
(fn write-value [pathname value]
(mktree (dirname pathname))
@ -49,12 +83,11 @@
(self:wait))))
(fn open [directory]
(let [watcher (watch-fsevents directory)
(let [outputs-dir (append-path directory ".outputs")
has-file? #(file-exists? (append-path directory $1))
outputs-dir (append-path directory ".outputs")
watcher (watch-fsevents outputs-dir)
properties-dir (append-path directory ".properties")]
{
:wait #(watcher:read)
:ready? (fn [self]
(and (has-file? ".outputs/state")
(not (has-file? ".outputs/.lock"))))
@ -66,6 +99,7 @@
(or
(read-value (append-path outputs-dir filename))
(read-value (append-path properties-dir filename)))))
:wait #(watcher:wait)
:close #(watcher:close)
:fileno #(watcher:fileno)
: events