swift: Fix for multiple mounts on the same mount point.

When swift server receives multiple requests on a volume and if the
volume is not mounted before hand, for each request swift tries to
mount the GlusterFS volume on the mount point. This process is racy
and may mount multiple times on the same mount point.

Also added a new option object_only in fs.conf which should be enabled
only if the user requires ReST interface and will have better performance.
By default it is set "off".

Change-Id: Ie1718554c5aaf577e823bbd84da8e78d803e954d
BUG: 821310
Signed-off-by: Mohammed Junaid <junaid@redhat.com>
Reviewed-on: http://review.gluster.com/3478
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Vijay Bellur <vijay@gluster.com>

1 files changed, 36 insertions, 8 deletions

diff --git a/swift/1.4.8/plugins/Glusterfs.py b/swift/1.4.8/plugins/Glusterfs.py
index eb8d535db..5e191e1bd 100644
--- a/swift/1.4.8/plugins/Glusterfs.py
+++ b/swift/1.4.8/plugins/Glusterfs.py
@@ -13,10 +13,11 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 import logging
-import os
+import os, fcntl, time
 from ConfigParser import ConfigParser
 from swift.common.utils import TRUE_VALUES
 from hashlib import md5
+from swift.plugins.utils import mkdirs
 
 class Glusterfs(object):
     def __init__(self):
@@ -27,16 +28,43 @@ class Glusterfs(object):
         self.auth_account = self.fs_conf.get('DEFAULT', 'auth_account', 'auth')
         self.mount_ip = self.fs_conf.get('DEFAULT', 'mount_ip', 'localhost')
         self.remote_cluster = self.fs_conf.get('DEFAULT', 'remote_cluster', False) in TRUE_VALUES
+        self.object_only = self.fs_conf.get('DEFAULT', 'object_only', "no") in TRUE_VALUES
+
+    def busy_wait(self, mount_path):
+        # Iterate for definite number of time over a given
+        # interval for successful mount
+        for i in range(0, 5):
+            if os.path.ismount(os.path.join(mount_path)):
+                return True
+            time.sleep(2)
+        return False
 
     def mount(self, account):
-        export = self.get_export_from_account_id(account)
         mount_path = os.path.join(self.mount_path, account)
-        mnt_cmd = 'mount -t glusterfs %s:%s %s' % (self.mount_ip, export, \
-                                                   mount_path)
-        if os.system(mnt_cmd) or \
-        not os.path.exists(os.path.join(mount_path)):
-            raise Exception('Mount failed %s: %s' % (self.name, mnt_cmd))
-            return False
+        export = self.get_export_from_account_id(account)
+
+        pid_dir  = "/var/lib/glusterd/vols/%s/run/" %export
+        pid_file = os.path.join(pid_dir, 'swift.pid');
+
+        if not os.path.exists(pid_dir):
+            mkdirs(pid_dir)
+
+        fd = os.open(pid_file, os.O_CREAT|os.O_RDWR)
+        with os.fdopen(fd, 'r+b') as f:
+            try:
+                fcntl.lockf(f, fcntl.LOCK_EX|fcntl.LOCK_NB)
+            except:
+                ex = sys.exc_info()[1]
+                if isinstance(ex, IOError) and ex.errno in (EACCES, EAGAIN):
+                # This means that some other process is mounting the
+                # filesystem, so wait for the mount process to complete
+                    return self.busy_wait(mount_path)
+
+            mnt_cmd = 'mount -t glusterfs %s:%s %s' % (self.mount_ip, export, \
+                                                       mount_path)
+            if os.system(mnt_cmd) or not self.busy_wait(mount_path):
+                raise Exception('Mount failed %s: %s' % (self.name, mnt_cmd))
+                return False
         return True
 
     def unmount(self, mount_path):