Use SLO by default for segmented uploads if the cluster supports it

We've had SLO for nearly ten years, and it is preferable for most
use-cases. It's time to default to SLO rather than DLO.

Add a new --use-dlo option to give users a way to return to old
behavior; ensure there is still a --use-slo option so we don't break
existing scripts that may use it.

UpgradeImpact:
==============
The default segmented-upload behavior has changed; Static Large Objects
are now used by default rather than Dynamic Large Objects. To revert to
the old behavior:

* CLI users may use the new `--use-dlo` option
* Service API users may explicitly set `use_slo` to False in their
  options dicts

Change-Id: Iebcd64ced8eab6efebb9f02a0c4be6bf6338cb3b

2 files changed, 27 insertions, 9 deletions

diff --git a/swiftclient/service.py b/swiftclient/service.py
index e905ea6..dd71409 100644
--- a/swiftclient/service.py
+++ b/swiftclient/service.py
@@ -196,7 +196,7 @@ _default_global_options = _build_default_global_options()
 _default_local_options = {
     'sync_to': None,
     'sync_key': None,
-    'use_slo': False,
+    'use_slo': None,
     'segment_size': None,
     'segment_container': None,
     'leave_segments': False,
@@ -1467,7 +1467,7 @@ class SwiftService:
                                 'meta': [],
                                 'header': [],
                                 'segment_size': None,
-                                'use_slo': False,
+                                'use_slo': True,
                                 'segment_container': None,
                                 'leave_segments': False,
                                 'changed': None,
@@ -1493,6 +1493,18 @@ class SwiftService:
         except ValueError:
             raise SwiftError('Segment size should be an integer value')
 
+        if segment_size and options['use_slo'] is None:
+            try:
+                cap_result = self.capabilities()
+            except ClientException:
+                # pre-info swift, maybe? assume no slo middleware
+                options['use_slo'] = False
+            else:
+                if not cap_result['success']:
+                    options['use_slo'] = False
+                else:
+                    options['use_slo'] = 'slo' in cap_result['capabilities']
+
         # Incase we have a psudeo-folder path for <container> arg, derive
         # the container name from the top path and prepend the rest to
         # the object name. (same as passing --object-name).
diff --git a/swiftclient/shell.py b/swiftclient/shell.py
index 882a1c0..319141d 100755
--- a/swiftclient/shell.py
+++ b/swiftclient/shell.py
@@ -978,8 +978,8 @@ def st_copy(parser, args, output_manager, return_parser=False):
 st_upload_options = '''[--changed] [--skip-identical] [--segment-size <size>]
                     [--segment-container <container>] [--leave-segments]
                     [--object-threads <thread>] [--segment-threads <threads>]
-                    [--meta <name:value>] [--header <header>]
-                    [--use-slo] [--ignore-checksum] [--skip-container-put]
+                    [--meta <name:value>] [--header <header>] [--use-slo]
+                    [--use-dlo] [--ignore-checksum] [--skip-container-put]
                     [--object-name <object-name>]
                     <container> <file_or_directory> [<file_or_directory>] [...]
 '''
@@ -1024,8 +1024,11 @@ Optional arguments:
                         repeated. Example: -H "content-type:text/plain"
                          -H "Content-Length: 4000".
   --use-slo             When used in conjunction with --segment-size it will
-                        create a Static Large Object instead of the default
-                        Dynamic Large Object.
+                        create a Static Large Object. Deprecated; this is now
+                        the default behavior when the cluster supports it.
+  --use-dlo             When used in conjunction with --segment-size it will
+                        create a Dynamic Large Object. May be useful with old
+                        swift clusters.
   --ignore-checksum     Turn off checksum validation for uploads.
   --skip-container-put  Assume all necessary containers already exist; don't
                         automatically try to create them.
@@ -1087,10 +1090,13 @@ def st_upload(parser, args, output_manager, return_parser=False):
         ' This option may be repeated. Example: -H "content-type:text/plain" '
         '-H "Content-Length: 4000"')
     parser.add_argument(
-        '--use-slo', action='store_true', default=False,
+        '--use-slo', action='store_true', default=None,
         help='When used in conjunction with --segment-size, it will '
-        'create a Static Large Object instead of the default '
-        'Dynamic Large Object.')
+        'create a Static Large Object.')
+    parser.add_argument(
+        '--use-dlo', action='store_false', dest="use_slo", default=None,
+        help='When used in conjunction with --segment-size, it will '
+        'create a Dynamic Large Object.')
     parser.add_argument(
         '--object-name', dest='object_name',
         help='Upload file and name object to <object-name> or upload dir and '