From cb7f7bca5ebfdd6d750aa69f8413801b0ecc0906 Mon Sep 17 00:00:00 2001
From: Nikhil Komawar <nik.komawar@gmail.com>
Date: Thu, 1 Sep 2016 18:48:05 -0400
Subject: [PATCH] Always return a sorted list of drivers for configs

glance.store entry point used in Glance for the store library is
resulting in generating random order in each run of the ``tox -e
genconfig`` command. This is because of the unsorted iterator returned
by the stevedore extension manager [1, 2].

This commit fixes that and returs a deterministic, sorted list of
drivers to generate the configs in Glance.

Example scenario is at change Iea2c538b37182191445cc5c1f8b2d9dceed06343

Closes-Bug: 1619487

[1] https://github.com/openstack/glance_store/blob/22fa2b08e76a8ebc39ade92504aeafb0bf8d2f8c/glance_store/backend.py#L135
[2] http://docs.openstack.org/developer/stevedore/managers.html#stevedore.extension.ExtensionManager.__iter__

Co-Authored-By: Joshua Harlow <jxharlow@godaddy.com>

(cherry picked from commits b5833a87236183444589f3f93fba8641eb6c520a and
04ef385759e535881e01d439c93d5bfae4841940)

Change-Id: I3146b8597a5d89da49b84d6653edacc3067c2c71
---
 glance_store/backend.py                          |  7 ++++++-
 ...ted-drivers-for-configs-a905f07d3bf9c973.yaml | 16 ++++++++++++++++
 2 files changed, 22 insertions(+), 1 deletion(-)
 create mode 100644 releasenotes/notes/sorted-drivers-for-configs-a905f07d3bf9c973.yaml

diff --git a/glance_store/backend.py b/glance_store/backend.py
index ba9ac644..8a2505e0 100644
--- a/glance_store/backend.py
+++ b/glance_store/backend.py
@@ -132,7 +132,12 @@ def _list_opts():
     driver_opts = []
     mgr = extension.ExtensionManager('glance_store.drivers')
     # NOTE(zhiyan): Handle available drivers entry_points provided
-    drivers = [ext.name for ext in mgr]
+    # NOTE(nikhil): Return a sorted list of drivers so that the oslo config
+    # generator can use that order to keep generating configuration file in a
+    # consistent manner. If this order is not preserved, in some cases the
+    # downstream packagers may see a long diff of the changes though not
+    # relevant as only order has changed. See some more details at bug 1619487.
+    drivers = sorted([ext.name for ext in mgr])
     handled_drivers = []  # Used to handle backwards-compatible entries
     for store_entry in drivers:
         driver_cls = _load_store(None, store_entry, False)
diff --git a/releasenotes/notes/sorted-drivers-for-configs-a905f07d3bf9c973.yaml b/releasenotes/notes/sorted-drivers-for-configs-a905f07d3bf9c973.yaml
new file mode 100644
index 00000000..a50630f1
--- /dev/null
+++ b/releasenotes/notes/sorted-drivers-for-configs-a905f07d3bf9c973.yaml
@@ -0,0 +1,16 @@
+---
+prelude: >
+    Return list of store drivers in sorted order for
+    generating configs. More info in ``Upgrade Notes``
+    and ``Bug Fixes`` section.
+upgrade:
+  - This version of glance_store will result in Glance
+    generating the configs in a sorted (deterministic)
+    order. So, preferably store releases on or after this
+    should be used for generating any new configs if the
+    mismatched ordering of the configs results in an issue
+    in your environment.
+fixes:
+  - Bug 1619487 is fixed which was causing random order of
+    the generation of configs in Glance. See ``upgrade``
+    section for more details.