Reduce the number of stat/fstat system calls made

This address BZ 868086, https://bugzilla.redhat.com/show_bug.cgi?id=868086

This refactoring consolidates the code a bit, and uses os.stat calls to get
all the information in one call when gathering the metadata for an object. The
five stat system calls (invoked via all the os.path.*() calls) have been
reduced to one.

We also added a unit test for the one new behavior where get_object_metadata()
will now throw an OSError exception if it has a problem stat'ing a file that
exists.

Change-Id: Iad5410c77938af68a47be757a3170abd201adeb0
BUG: 868086
Signed-off-by: Peter Portante <peter.portante@redhat.com>
Reviewed-on: http://review.gluster.org/4112
Reviewed-by: Kaleb KEITHLEY <kkeithle@redhat.com>
Reviewed-by: Mohammed Junaid <junaid@redhat.com>
Tested-by: Anand Avati <avati@redhat.com>

2 files changed, 34 insertions, 39 deletions

diff --git a/swift/1.4.8/plugins/utils.py b/swift/1.4.8/plugins/utils.py
index 289420cb93f..a25cbc3b8f4 100644
--- a/swift/1.4.8/plugins/utils.py
+++ b/swift/1.4.8/plugins/utils.py
@@ -525,50 +525,36 @@ def get_account_details(acc_path, memcache=None):
         return get_account_details_from_fs(acc_path, memcache)
 
 def get_etag(path):
-    etag = None
-    if os.path.exists(path):
-        etag = md5()
-        if not os.path.isdir(path):
-            fp = open(path, 'rb')
-            if fp:
-                while True:
-                    chunk = fp.read(CHUNK_SIZE)
-                    if chunk:
-                        etag.update(chunk)
-                    else:
-                        break
-                fp.close()
-
-        etag = etag.hexdigest()
-
-    return etag
-
+    etag = md5()
+    with open(path, 'rb') as fp:
+        while True:
+            chunk = fp.read(CHUNK_SIZE)
+            if chunk:
+                etag.update(chunk)
+            else:
+                break
+    return etag.hexdigest()
 
 def get_object_metadata(obj_path):
     """
     Return metadata of object.
     """
-    metadata = {}
-    if os.path.exists(obj_path):
-        if not os.path.isdir(obj_path):
-            metadata = {
-                    X_TIMESTAMP: normalize_timestamp(os.path.getctime(obj_path)),
-                    X_CONTENT_TYPE: FILE_TYPE,
-                    X_ETAG: get_etag(obj_path),
-                    X_CONTENT_LENGTH: os.path.getsize(obj_path),
-                    X_TYPE: OBJECT,
-                    X_OBJECT_TYPE: FILE,
-                }
-        else:
-            metadata = {
-                    X_TIMESTAMP: normalize_timestamp(os.path.getctime(obj_path)),
-                    X_CONTENT_TYPE: DIR_TYPE,
-                    X_ETAG: get_etag(obj_path),
-                    X_CONTENT_LENGTH: 0,
-                    X_TYPE: OBJECT,
-                    X_OBJECT_TYPE: DIR,
-                }
-
+    try:
+        stats = os.stat(obj_path)
+    except OSError as e:
+        if e.errno != errno.ENOENT:
+            raise
+        metadata = {}
+    else:
+        is_dir = (stats.st_mode & 0040000) != 0
+        metadata = {
+            X_TYPE: OBJECT,
+            X_TIMESTAMP: normalize_timestamp(stats.st_ctime),
+            X_CONTENT_TYPE: DIR_TYPE if is_dir else FILE_TYPE,
+            X_OBJECT_TYPE: DIR if is_dir else FILE,
+            X_CONTENT_LENGTH: 0 if is_dir else stats.st_size,
+            X_ETAG: md5().hexdigest() if is_dir else get_etag(obj_path),
+            }
     return metadata
 
 def _add_timestamp(metadata_i):
diff --git a/swift/1.4.8/test/unit/plugins/test_utils.py b/swift/1.4.8/test/unit/plugins/test_utils.py
index 944d118926a..70081a7d26e 100644
--- a/swift/1.4.8/test/unit/plugins/test_utils.py
+++ b/swift/1.4.8/test/unit/plugins/test_utils.py
@@ -312,6 +312,15 @@ class TestUtils(unittest.TestCase):
         md = utils.get_object_metadata("/tmp/doesNotEx1st")
         assert md == {}
 
+    def test_get_object_metadata_err(self):
+        tf = tempfile.NamedTemporaryFile()
+        try:
+            md = utils.get_object_metadata(os.path.join(tf.name,"doesNotEx1st"))
+        except OSError as e:
+            assert e.errno != errno.ENOENT
+        else:
+            self.fail("Expected exception")
+
     obj_keys = (utils.X_TIMESTAMP, utils.X_CONTENT_TYPE, utils.X_ETAG,
                 utils.X_CONTENT_LENGTH, utils.X_TYPE, utils.X_OBJECT_TYPE)