Use gzip for snapshots

On the 15G snapshot data gz is 10 times faster than xz while compression
rate is just 36% against 50% with gzip.
For the pattern "create once - download once" this looks like a
reasonable solution.

Change-Id: I5d2ce3681ec6555a8994bb39def907006be8b79f
Closes-Bug: #1546023

shotgun/manager.py

@@ -52,7 +52,7 @@ class Manager(object):
                            excludes)
 
             with open(self.conf.lastdump, "w") as fo:
-                fo.write("{0}.tar.xz".format(self.conf.target))
+                fo.write("{0}.tar.gz".format(self.conf.target))
         except IOError as e:
             if e.errno == errno.ENOSPC:
                 logger.error("Not enough space in "
@@ -60,7 +60,7 @@ class Manager(object):
                 self.clear_target()
             raise
 
-        return "{0}.tar.xz".format(self.conf.target)
+        return "{0}.tar.gz".format(self.conf.target)
 
     def action_single(self, obj, action='snapshot'):
         driver = Driver.getDriver(obj, self.conf)

shotgun/test/test_utils.py

@@ -58,7 +58,7 @@ class TestUtils(base.BaseTestCase):
         self.assertEqual(compress_env['XZ_OPT'], level)
         self.assertEqual(
             compress_call[0][0],
-            'tar chJvf /path/target.tar.xz -C /path target')
+            'tar chzvf /path/target.tar.gz -C /path target')
 
         self.assertEqual(rm_call[0][0], 'rm -r /path/target')
 
@@ -77,7 +77,7 @@ class TestUtils(base.BaseTestCase):
         self.assertEqual(compress_env['XZ_OPT'], level)
         self.assertEqual(
             compress_call[0][0],
-            'tar chJvf /path/target.tar.xz -C /path target '
+            'tar chzvf /path/target.tar.gz -C /path target '
             '--exclude /path/to/exclude1 --exclude /path/to/exclude2')
 
 

shotgun/utils.py

@@ -70,7 +70,7 @@ def compress(target, level, keep_target=False, exclude=None):
 
     env = copy.deepcopy(os.environ)
     env['XZ_OPT'] = level
-    execute("tar chJvf {0}.tar.xz -C {1} {2}{3}"
+    execute("tar chzvf {0}.tar.gz -C {1} {2}{3}"
             "".format(target,
                       os.path.dirname(target),
                       os.path.basename(target),