feat(disk_setup) add timeout

In a cloud environment, sometimes disks will attach while cloud-init is
running and get missed. This adds a configurable timeout to wait for
those disks.

Signed-off-by: Florian Klink <flokli@flokli.de>

cloudinit/config/cc_disk_setup.py

@@ -131,6 +131,13 @@ def alias_to_device(cand):
                 LOG.warning("Invalid disk definition for %s", disk)
                 continue
 
+            if definition.get("timeout"):
+                tmout = int(definition.get("timeout"))
+                need = util.wait_for_files([disk],
+                                           maxwait=tmout,
+                                           naplen=0.1)
+                if len(need) > 0:
+                    log.warning("Timeout expired waiting for %s" % disk)
             try:
                 LOG.debug("Creating new partition table/disk")
                 util.log_time(

doc/examples/cloud-config-disk-setup.txt

@@ -98,6 +98,7 @@ disk_setup:
 #       table_type: 'mbr'
 #       layout: <LAYOUT|BOOL>
 #       overwrite: <BOOL>
+#       timeout: <INT>
 #
 # Where:
 #   <DEVICE>: The name of the device. 'ephemeralX' and 'swap' are special
@@ -160,6 +161,11 @@ disk_setup:
 #                   done blindly. USE with caution, you can do things you
 #                   really, really don't want to do.
 #
+#   timeout=<INT>: Seconds to wait for a disk to appear. If omitted, no wait
+#               is performed. This is useful if a cloud provider has late or
+#               inconsistent disk attachments and you need a delay.
+#
+#
 #
 # fs_setup: Setup the filesystem
 # ------------------------------