Add activate_datasource, for datasource specific code paths.

This adds a call to 'activate_datasource'.  That will be called
during init stage (or init-local in the event of a 'local' dsmode).
It is present so that the datasource can do platform specific operations
that may be necessary.  It is passed the fully rendered cloud-config
and whether or not the instance is a new instance.

The Azure datasource uses this to address formatting of the ephemeral
devices.  It does so by
 a.) waiting for the device to come online
 b.) removing the marker files for the disk_setup and mounts modules
     if it finds that the ephemeral device has been reset.

LP: #1611074

2 files changed, 116 insertions, 95 deletions

diff --git a/cloudinit/sources/DataSourceAzure.py b/cloudinit/sources/DataSourceAzure.py
index b802b03e..22f9004a 100644
--- a/cloudinit/sources/DataSourceAzure.py
+++ b/cloudinit/sources/DataSourceAzure.py
@@ -19,7 +19,6 @@
 import base64
 import contextlib
 import crypt
-import fnmatch
 from functools import partial
 import os
 import os.path
@@ -28,7 +27,6 @@ from xml.dom import minidom
 import xml.etree.ElementTree as ET
 
 from cloudinit import log as logging
-from cloudinit.settings import PER_ALWAYS
 from cloudinit import sources
 from cloudinit.sources.helpers.azure import get_metadata_from_fabric
 from cloudinit import util
@@ -42,6 +40,9 @@ BOUNCE_COMMAND = [
     'sh', '-xc',
     "i=$interface; x=0; ifdown $i || x=$?; ifup $i || x=$?; exit $x"
 ]
+# azure systems will always have a resource disk, and 66-azure-ephemeral.rules
+# ensures that it gets linked to this path.
+RESOURCE_DISK_PATH = '/dev/disk/cloud/azure_resource'
 
 BUILTIN_DS_CONFIG = {
     'agent_command': AGENT_START,
@@ -53,7 +54,7 @@ BUILTIN_DS_CONFIG = {
         'command': BOUNCE_COMMAND,
         'hostname_command': 'hostname',
     },
-    'disk_aliases': {'ephemeral0': '/dev/sdb'},
+    'disk_aliases': {'ephemeral0': RESOURCE_DISK_PATH},
     'dhclient_lease_file': '/var/lib/dhcp/dhclient.eth0.leases',
 }
 
@@ -245,15 +246,6 @@ class DataSourceAzureNet(sources.DataSource):
         self.metadata['instance-id'] = util.read_dmi_data('system-uuid')
         self.metadata.update(fabric_data)
 
-        found_ephemeral = find_fabric_formatted_ephemeral_disk()
-        if found_ephemeral:
-            self.ds_cfg['disk_aliases']['ephemeral0'] = found_ephemeral
-            LOG.debug("using detected ephemeral0 of %s", found_ephemeral)
-
-        cc_modules_override = support_new_ephemeral(self.sys_cfg)
-        if cc_modules_override:
-            self.cfg['cloud_init_modules'] = cc_modules_override
-
         return True
 
     def device_name_to_device(self, name):
@@ -266,97 +258,104 @@ class DataSourceAzureNet(sources.DataSource):
         # quickly (local check only) if self.instance_id is still valid
         return sources.instance_id_matches_system_uuid(self.get_instance_id())
 
-
-def count_files(mp):
-    return len(fnmatch.filter(os.listdir(mp), '*[!cdrom]*'))
+    def activate(self, cfg, is_new_instance):
+        address_ephemeral_resize(is_new_instance=is_new_instance)
+        return
 
 
-def find_fabric_formatted_ephemeral_part():
-    """
-    Locate the first fabric formatted ephemeral device.
-    """
-    potential_locations = ['/dev/disk/cloud/azure_resource-part1',
-                           '/dev/disk/azure/resource-part1']
-    device_location = None
-    for potential_location in potential_locations:
-        if os.path.exists(potential_location):
-            device_location = potential_location
+def can_dev_be_reformatted(devpath):
+    # determine if the ephemeral block device path devpath
+    # is newly formatted after a resize.
+    if not os.path.exists(devpath):
+        return False, 'device %s does not exist' % devpath
+
+    realpath = os.path.realpath(devpath)
+    LOG.debug('Resolving realpath of %s -> %s', devpath, realpath)
+
+    # it is possible that the block device might exist, but the kernel
+    # have not yet read the partition table and sent events.  we udevadm settle
+    # to hope to resolve that.  Better here would probably be to test and see,
+    # and then settle if we didn't find anything and try again.
+    if util.which("udevadm"):
+        util.subp(["udevadm", "settle"])
+
+    # devpath of /dev/sd[a-z] or /dev/disk/cloud/azure_resource
+    # where partitions are "<devpath>1" or "<devpath>-part1" or "<devpath>p1"
+    part1path = None
+    for suff in ("-part", "p", ""):
+        cand = devpath + suff + "1"
+        if os.path.exists(cand):
+            if os.path.exists(devpath + suff + "2"):
+                msg = ('device %s had more than 1 partition: %s, %s' %
+                       devpath, cand, devpath + suff + "2")
+                return False, msg
+            part1path = cand
             break
-    if device_location is None:
-        LOG.debug("no azure resource disk partition path found")
-        return None
-    ntfs_devices = util.find_devs_with("TYPE=ntfs")
-    real_device = os.path.realpath(device_location)
-    if real_device in ntfs_devices:
-        return device_location
-    LOG.debug("'%s' existed (%s) but was not ntfs formated",
-              device_location, real_device)
-    return None
-
-
-def find_fabric_formatted_ephemeral_disk():
-    """
-    Get the ephemeral disk.
-    """
-    part_dev = find_fabric_formatted_ephemeral_part()
-    if part_dev:
-        return part_dev.split('-')[0]
-    return None
 
+    if part1path is None:
+        return False, 'device %s was not partitioned' % devpath
 
-def support_new_ephemeral(cfg):
-    """
-    Windows Azure makes ephemeral devices ephemeral to boot; a ephemeral device
-    may be presented as a fresh device, or not.
+    real_part1path = os.path.realpath(part1path)
+    ntfs_devices = util.find_devs_with("TYPE=ntfs", no_cache=True)
+    LOG.debug('ntfs_devices found = %s', ntfs_devices)
+    if real_part1path not in ntfs_devices:
+        msg = ('partition 1 (%s -> %s) on device %s was not ntfs formatted' %
+               (part1path, real_part1path, devpath))
+        return False, msg
 
-    Since the knowledge of when a disk is supposed to be plowed under is
-    specific to Windows Azure, the logic resides here in the datasource. When a
-    new ephemeral device is detected, cloud-init overrides the default
-    frequency for both disk-setup and mounts for the current boot only.
-    """
-    device = find_fabric_formatted_ephemeral_part()
-    if not device:
-        LOG.debug("no default fabric formated ephemeral0.1 found")
-        return None
-    LOG.debug("fabric formated ephemeral0.1 device at %s", device)
+    def count_files(mp):
+        ignored = {'dataloss_warning_readme.txt'}
+        return len([f for f in os.listdir(mp) if f.lower() not in ignored])
 
-    file_count = 0
+    bmsg = ('partition 1 (%s -> %s) on device %s was ntfs formatted' %
+            (part1path, real_part1path, devpath))
     try:
-        file_count = util.mount_cb(device, count_files)
-    except Exception:
-        return None
-    LOG.debug("fabric prepared ephmeral0.1 has %s files on it", file_count)
-
-    if file_count >= 1:
-        LOG.debug("fabric prepared ephemeral0.1 will be preserved")
-        return None
+        file_count = util.mount_cb(part1path, count_files)
+    except util.MountFailedError as e:
+        return False, bmsg + ' but mount of %s failed: %s' % (part1path, e)
+
+    if file_count != 0:
+        return False, bmsg + ' but had %d files on it.' % file_count
+
+    return True, bmsg + ' and had no important files. Safe for reformatting.'
+
+
+def address_ephemeral_resize(devpath=RESOURCE_DISK_PATH, maxwait=120,
+                             is_new_instance=False):
+    # wait for ephemeral disk to come up
+    naplen = .2
+    missing = wait_for_files([devpath], maxwait=maxwait, naplen=naplen,
+                             log_pre="Azure ephemeral disk: ")
+
+    if missing:
+        LOG.warn("ephemeral device '%s' did not appear after %d seconds.",
+                 devpath, maxwait)
+        return
+
+    result = False
+    msg = None
+    if is_new_instance:
+        result, msg = (True, "First instance boot.")
     else:
-        # if device was already mounted, then we need to unmount it
-        # race conditions could allow for a check-then-unmount
-        # to have a false positive. so just unmount and then check.
-        try:
-            util.subp(['umount', device])
-        except util.ProcessExecutionError as e:
-            if device in util.mounts():
-                LOG.warn("Failed to unmount %s, will not reformat.", device)
-                LOG.debug("Failed umount: %s", e)
-                return None
-
-    LOG.debug("cloud-init will format ephemeral0.1 this boot.")
-    LOG.debug("setting disk_setup and mounts modules 'always' for this boot")
-
-    cc_modules = cfg.get('cloud_init_modules')
-    if not cc_modules:
-        return None
-
-    mod_list = []
-    for mod in cc_modules:
-        if mod in ("disk_setup", "mounts"):
-            mod_list.append([mod, PER_ALWAYS])
-            LOG.debug("set module '%s' to 'always' for this boot", mod)
+        result, msg = can_dev_be_reformatted(devpath)
+
+    LOG.debug("reformattable=%s: %s" % (result, msg))
+    if not result:
+        return
+
+    for mod in ['disk_setup', 'mounts']:
+        sempath = '/var/lib/cloud/instance/sem/config_' + mod
+        bmsg = 'Marker "%s" for module "%s"' % (sempath, mod)
+        if os.path.exists(sempath):
+            try:
+                os.unlink(sempath)
+                LOG.debug(bmsg + " removed.")
+            except Exception as e:
+                # python3 throws FileNotFoundError, python2 throws OSError
+                LOG.warn(bmsg + ": remove failed! (%s)" % e)
         else:
-            mod_list.append(mod)
-    return mod_list
+            LOG.debug(bmsg + " did not exist.")
+    return
 
 
 def perform_hostname_bounce(hostname, cfg, prev_hostname):
@@ -408,15 +407,25 @@ def pubkeys_from_crt_files(flist):
     return pubkeys
 
 
-def wait_for_files(flist, maxwait=60, naplen=.5):
+def wait_for_files(flist, maxwait=60, naplen=.5, log_pre=""):
     need = set(flist)
     waited = 0
-    while waited < maxwait:
+    while True:
         need -= set([f for f in need if os.path.exists(f)])
         if len(need) == 0:
+            LOG.debug("%sAll files appeared after %s seconds: %s",
+                      log_pre, waited, flist)
             return []
+        if waited == 0:
+            LOG.info("%sWaiting up to %s seconds for the following files: %s",
+                     log_pre, maxwait, flist)
+        if waited + naplen > maxwait:
+            break
         time.sleep(naplen)
         waited += naplen
+
+    LOG.warn("%sStill missing files after %s seconds: %s",
+             log_pre, maxwait, need)
     return need
 
 
diff --git a/cloudinit/sources/__init__.py b/cloudinit/sources/__init__.py
index d1395270..13fb7c62 100644
--- a/cloudinit/sources/__init__.py
+++ b/cloudinit/sources/__init__.py
@@ -261,6 +261,18 @@ class DataSource(object):
     def first_instance_boot(self):
         return
 
+    def activate(self, cfg, is_new_instance):
+        """activate(cfg, is_new_instance)
+
+        This is called before the init_modules will be called.
+        The cfg is fully up to date config, it contains a merged view of
+           system config, datasource config, user config, vendor config.
+        It should be used rather than the sys_cfg passed to __init__.
+
+        is_new_instance is a boolean indicating if this is a new instance.
+        """
+        return
+
 
 def normalize_pubkey_data(pubkey_data):
     keys = []