Merge lp:~smoser/cloud-init/trunk.improve-wait into lp:~cloud-init-dev/cloud-init/trunk

[Scott Moser]

improve how cloud-init-wait waits

  since we run from a udev event, this is sufficient.
  udev settle will exit when either of
   a.) the file exists
   b.) the udev event queue has all been processed.

  Since cloud-init-wait is being run as a udev event, 'b' cannot
  be satisfied until it finishes. Thus, this essentially becomes a
  inotify based wait for the file /run/cloud-init/network-config-ready
  and no loops are needed.

[Martin Pitt (pitti)]

This looks nice indeed, thanks!

review: Approve

[Dimitri John Ledkov (xnox)]

review: Approve

=== modified file 'udev/cloud-init-wait'
--- udev/cloud-init-wait	2016-03-21 02:31:21 +0000
+++ udev/cloud-init-wait	2016-03-28 18:55:53 +0000
@@ -3,16 +3,13 @@
 CI_NET_READY="/run/cloud-init/network-config-ready"
 LOG="/run/cloud-init/${0##*/}.log"
 LOG_INIT=0
+MAX_WAIT=60
 DEBUG=0
 
 block_until_ready() {
-    local fname="$1"
-    local naplen="$2" max="$3" n=0
-    while ! [ -f "$fname" ]; do
-        n=$(($n+1))
-        [ "$n" -ge "$max" ] && return 1
-        sleep $naplen
-    done
+    local fname="$1" max="$2"
+    [ -f "$fname" ] && return 0
+    udevadm settle "--timeout=$max" "--exit-if-exists=$fname"
 }
 
 log() {
@@ -56,7 +53,7 @@
         return 0
     fi
 
-    block_until_ready "$readyfile" .1 600 ||
+    block_until_ready "$readyfile" "$MAX_WAIT" ||
        { log "failed waiting for ready on $INTERFACE"; return 1; }
 
     log "net config ready"