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simplify protocol for watchers of service output directories

Previously: the service wrote a timestamp and the receiver
read and parsed it to see if there was new data

Now: the service writes and removes a .lock file to prevent
the receiver reading partial data. The receiver is responsible
for remembering the *previous* state and only updating if it's changed
This commit is contained in:
Daniel Barlow 2023-07-02 00:52:18 +01:00
parent 5532144747
commit 3900683413
2 changed files with 83 additions and 51 deletions

View File

@ -1,6 +1,39 @@
(local inotify (require :inotify))
(fn merge [table1 table2]
(collect [k v (pairs table2) &into table1]
k v))
(fn split [sep string]
(icollect [v (string.gmatch string (.. "([^" sep "]+)"))]
v))
(fn parse-prefix [str]
(fn parse-extra [s]
(let [out {}]
(each [name val (string.gmatch s ",(.-)=([^,]+)")]
(tset out name val))
out))
(let [(prefix len preferred valid extra)
(string.match str "(.-)::/(%d+),(%d+),(%d+)(.*)$")]
(merge {: prefix : len : preferred : valid} (parse-extra extra))))
;; Format: <prefix>/<length>,preferred,valid[,excluded=<excluded-prefix>/<length>][,class=<prefix class #>]
;;(parse-prefix "2001:8b0:de3a:40dc::/64,7198,7198")
;;(parse-prefix "2001:8b0:de3a:1001::/64,7198,7188,excluded=1/2,thi=10")
(fn file-exists? [name]
(match (io.open name :r)
f (do (f:close) true)
_ false))
(fn read-line [name]
(with-open [f (assert (io.open name :r) (.. "can't open file " name))]
(f:read "*l")))
(fn watch-fsevents [directory-name]
(let [handle (inotify.init)]
(handle:addwatch directory-name
@ -13,58 +46,56 @@
inotify.IN_CLOSE_WRITE)
handle))
(fn watch-directory [pathname]
(let [watcher (watch-fsevents pathname)]
{
:has-file? (fn [_ filename] (file-exists? (.. pathname "/" filename)))
:wait-events (fn [] (watcher:read))
:ready? (fn [self]
(and (self:has-file? "state") (not (self:has-file? ".lock"))))
:read-line (fn [_ filename] (read-line (.. pathname "/" filename)))
:close #(watcher:close)
}))
(fn merge [table1 table2]
(collect [k v (pairs table2) &into table1]
k v))
(local bound-states
{ :bound true
:rebound true
:informed true
:updated true
:ra-updated true
})
(fn parse-extra [s]
(let [out {}]
(each [name val (string.gmatch s ",(.-)=([^,]+)")]
(tset out name val))
out))
; (local { : view } (require :fennel))
(fn parse-prefixes [prefixes]
(icollect [val (string.gmatch prefixes "([^ ]+)")]
(let [(prefix len preferred valid extra)
(string.match val "(.-)::/(%d+),(%d+),(%d+)(.*)$")]
(merge {: prefix : len : preferred : valid} (parse-extra extra))
)))
(fn changes [old-prefixes new-prefixes]
(let [added {}
deleted {}
old-set (collect [_ v (ipairs old-prefixes)] (values v true))
new-set (collect [_ v (ipairs new-prefixes)] (values v true))]
(each [_ prefix (ipairs new-prefixes)]
(if (not (. old-set prefix))
(table.insert added (parse-prefix prefix))))
(each [_ prefix (ipairs old-prefixes)]
(if (not (. new-set prefix))
(table.insert deleted (parse-prefix prefix))))
(values added deleted)))
;; Format: <prefix>/<length>,preferred,valid[,excluded=<excluded-prefix>/<length>][,class=<prefix class #>]
;; (parse-prefixes "2001:8b0:de3a:40dc::/64,7198,7198 2001:8b0:de3a:1001::/64,7198,7188,excluded=1/2,thi=10")
(fn file-exists? [name]
(match (io.open name :r)
f (do (f:close) true)
_ false))
(fn read-line [name]
(with-open [f (assert (io.open name :r) (.. "can't open file " name))]
(f:read "*l")))
(var last-update 0)
(fn event-time [directory]
(if (file-exists? (.. directory "/state"))
(tonumber (read-line (.. directory "/last-update")))
nil))
(fn wait-for-update [directory fsevents]
(while (<= (or (event-time directory) 0) last-update)
(fsevents:read))
(set last-update (event-time directory))
true)
;;(fn execute [s] (do (print s) true))
(fn execute [s] (assert (os.execute s)))
(let [[state-directory lan-device] arg
fsevents (watch-fsevents state-directory)]
(while (wait-for-update state-directory fsevents)
(match (read-line (.. state-directory "/state"))
(where (or :bound :rebound :informed :updated :ra-updated))
(let [[{ : prefix : len : preferred : valid }]
(parse-prefixes (read-line (.. state-directory "/prefixes")))]
(os.execute (.. "ip address add " prefix "::1/" len
" dev " lan-device)))
_ (os.exit 1))))
dir (watch-directory state-directory)]
(var prefixes [])
(while true
(while (not (dir:ready?)) (dir:wait-events))
(if (. bound-states (dir:read-line "state"))
(let [new-prefixes (split " " (dir:read-line "/prefixes"))
(added deleted) (changes prefixes new-prefixes)]
(each [_ p (ipairs added)]
(execute
(.. "ip address add " p.prefix "::1/" p.len " dev " lan-device)))
(each [_ p (ipairs deleted)]
(execute
(.. "ip address del " p.prefix "::1/" p.len " dev " lan-device)))
(set prefixes new-prefixes)))
(dir:wait-events)))

View File

@ -56,8 +56,9 @@
"unbound" false
"stopped" false
_ true)]
(write-value "last-update" (tostring (os.time)))
(write-value ".lock" (tostring (os.time)))
(write-value "ifname" ifname)
(write-value "state" state)
(os.remove (.. state-directory "/.lock"))
(when ready
(with-open [fd (io.open "/proc/self/fd/10" :w)] (fd:write "\n"))))