openstack/swift
Code Issues Proposed changes

Add optional locking to swift-ring-builder

Browse Source 
If invoked as 'swift-ring-builder-safe' the directory containing the builder
file provided will be locked (via lock_parent_directory()). This provides a
small safe guard against multiple instances of the swift-ring-builder (or
other utilities that observe this lock) from attempting to write to or read
the builder/ring files while operations are in progress.

This is particularly useful in environments where ring management has been
automated (via Chef or custom solutions) but the operator still occasionally
needs to manually interact with the ring.

DocImpact

Change-Id: Ia362744a8151a91bfb586d01da582906726852e6
This commit is contained in:
Florian Hines 2013-01-25 08:00:33 -08:00
parent 2f663ff9a0
commit 00dbad0825
3 changed files with 27 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
bin/swift-ring-builder
View File

@ -19,14 +19,14 @@ from array import array
from errno import EEXIST
from itertools import islice, izip
from os import mkdir
from os.path import basename, dirname, exists, join as pathjoin
from os.path import basename, abspath, dirname, exists, join as pathjoin
from sys import argv, exit
from textwrap import wrap
from time import time
from swift.common import exceptions
from swift.common.ring import RingBuilder
from swift.common.utils import lock_parent_directory
MAJOR_VERSION = 1
MINOR_VERSION = 3
@ -625,4 +625,12 @@ if __name__ == '__main__':
command = "default"
else:
command = argv[2]
Commands.__dict__.get(command, Commands.unknown)()
if argv[0].endswith('-safe'):
try:
with lock_parent_directory(abspath(argv[1]), 15):
Commands.__dict__.get(command, Commands.unknown)()
except exceptions.LockTimeout:
print "Ring/builder dir currently locked."
exit(2)
else:
Commands.__dict__.get(command, Commands.unknown)()

8
doc/manpages/swift-ring-builder.1
View File

@ -48,6 +48,14 @@ partitions will end up assigned to different devices, and therefore nearly all
data stored will have to be replicated to new locations. So, recovery from a
builder file loss is possible, but data will definitely be unreachable for an
extended time.
.PP
If invoked as 'swift-ring-builder-safe' the directory containing the builder
file provided will be locked (via a .lock file in the files parent directory).
This provides a basic safe guard against multiple instances of the swift-ring-builder
(or other utilities that observe this lock) from attempting to write to or read
the builder/ring files while operations are in progress. This can be useful in
environments where ring management has been automated but the operator still
needs to interact with the rings manually.
.SH SEARCH

8
doc/source/admin_guide.rst
View File

@ -53,6 +53,14 @@ Once you are done with all changes to the ring, the changes need to be
Once the new rings are built, they should be pushed out to all the servers
in the cluster.
Optionally, if invoked as 'swift-ring-builder-safe' the directory containing
the specified builder file will be locked (via a .lock file in the parent
directory). This provides a basic safe guard against multiple instances
of the swift-ring-builder (or other utilities that observe this lock) from
attempting to write to or read the builder/ring files while operations are in
progress. This can be useful in environments where ring management has been
automated but the operator still needs to interact with the rings manually.
-----------------------
Scripting Ring Creation
-----------------------