Limit OSD object name lengths for Jewel + ext4

As of the Ceph Jewel release, certain limitations apply to
OSD object name lengths: specifically if ext4 is in use for
block devices or a directory based OSD is configured, OSD's
must be configured to limit object name length:

  osd max object name len = 256
  osd max object namespace len = 64

This may cause problems storing objects with long names via
the ceph-radosgw charm or for direct users of RADOS.

Also ensure that ceph.conf as a final newline as ceph requires
this.

Change-Id: I26f1d8a6f9560b307929f294d2d637c92986cf41
Closes-Bug: 1580320
Closes-Bug: 1578403
(cherry picked from commit 53d09832e5)

hooks/ceph_hooks.py

@@ -278,6 +278,24 @@ def install():
     install_upstart_scripts()
 
 
+def use_short_objects():
+    '''
+    Determine whether OSD's should be configured with
+    limited object name lengths.
+
+    @return: boolean indicating whether OSD's should be limited
+    '''
+    if cmp_pkgrevno('ceph', "10.2.0") >= 0:
+        if config('osd-format') in ('ext4'):
+            return True
+        for device in config('osd-devices'):
+            if not device.startswith('/dev'):
+                # TODO: determine format of directory based
+                #       OSD location
+                return True
+    return False
+
+
 def emit_cephconf():
     mon_hosts = get_mon_hosts()
     log('Monitor hosts are ' + repr(mon_hosts))
@@ -299,6 +317,7 @@ def emit_cephconf():
         'ceph_cluster_network': cluster_network,
         'loglevel': config('loglevel'),
         'dio': str(config('use-direct-io')).lower(),
+        'short_object_len': use_short_objects(),
     }
 
     if config('prefer-ipv6'):

templates/ceph.conf

@@ -44,3 +44,8 @@ osd journal size = {{ osd_journal_size }}
 filestore xattr use omap = true
 journal dio = {{ dio }}
 
+{%- if short_object_len %}
+osd max object name len = 256
+osd max object namespace len = 64
+{% endif %}
+