Support unique labels for alembic branches

We plan to have all projects that integrate with Neutron use the same
alembic environment (Neutron's) instead of having a separate alembic
env.py in each repo. This means that each project will need to label
their contract and expand branches uniquely.

With this patch we add support for branch labels of the form
  'networking-foo-contract'
  'networking-foo-expand'

We also support the old labels ('contract' and 'expand') with the
intent of backporting this patch to Mitaka so that projects can be
backwards compatible when they update their alembic branch labels. A
best effort will be made to backport this patch to Liberty also.

Support has been removed for label names starting with a "liberty_"
prefix. Such labels temporarily existed during the Liberty cycle but
have now all been cleaned up.

Partial-Bug: #1497830

Change-Id: Ibf38b3125d5d404d57f3e8ef0c7ecfa56eaf8042

doc/source/devref/alembic_migrations.rst

@@ -418,6 +418,20 @@ following directive should be added in the contraction script::
     depends_on = ('<expansion-revision>',)
 
 
+Expand and Contract Branch Labeling
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Before the Newton release, neutron and each sub-project had its own alembic
+environment and each repo could re-use the labels ``contract`` and ``expand``
+for their alembic branches. With the Newton release, all neutron sub-projects
+use neutron's alembic environment, and this requires globally unique branch
+labels.
+
+To be compatible with the Newton release of neutron, all projects must use
+unique alembic branch labels of the form ``<project>-contract`` and
+``<project>-expand``.
+
+
 HEAD files for conflict management
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 

neutron/db/migration/alembic_migrations/versions/liberty/contract/30018084ec99_initial.py

@@ -25,7 +25,7 @@
 # revision identifiers, used by Alembic.
 revision = '30018084ec99'
 down_revision = 'kilo'
-branch_labels = (cli.CONTRACT_BRANCH,)
+branch_labels = ('neutron-' + cli.CONTRACT_BRANCH,)
 
 
 def upgrade():

neutron/db/migration/alembic_migrations/versions/liberty/expand/354db87e3225_nsxv_vdr_metadata.py

@@ -30,7 +30,7 @@
 # revision identifiers, used by Alembic.
 revision = '354db87e3225'
 down_revision = 'kilo'
-branch_labels = (cli.EXPAND_BRANCH,)
+branch_labels = ('neutron-' + cli.EXPAND_BRANCH,)
 
 
 def upgrade():

neutron/db/migration/autogen.py

@@ -54,7 +54,8 @@ def _migration_script_ops(context, directive, phase):
     version_path = cli._get_version_branch_path(
         context.config, release=cli.CURRENT_RELEASE, branch=phase)
     autogen_kwargs = {}
-    cli._check_bootstrap_new_branch(phase, version_path, autogen_kwargs)
+    cli._check_bootstrap_new_branch(context.config, phase, version_path,
+                                    autogen_kwargs)
 
     op = ops.MigrationScript(
         new_rev_id(),

neutron/db/migration/cli.py

@@ -93,11 +93,14 @@
 
 
 def do_alembic_command(config, cmd, revision=None, desc=None, **kwargs):
+    project = config.get_main_option('neutron_project')
     args = []
     if revision:
+        # We use unique branch labels from Newton onwards.
+        if revision.split('@')[0] in MIGRATION_BRANCHES:
+            revision = '-'.join([project, revision])
         args.append(revision)
 
-    project = config.get_main_option('neutron_project')
     if desc:
         alembic_util.msg(_('Running %(cmd)s (%(desc)s) for %(project)s ...') %
                          {'cmd': cmd, 'desc': desc, 'project': project})
@@ -142,13 +145,13 @@ def add_branch_options(parser):
 def _find_milestone_revisions(config, milestone, branch=None):
     """Return the revision(s) for a given milestone."""
     script = alembic_script.ScriptDirectory.from_config(config)
-    return [
-        (m.revision, label)
-        for m in _get_revisions(script)
-        for label in (m.branch_labels or [None])
-        if milestone in getattr(m.module, 'neutron_milestone', []) and
-        (branch is None or branch in m.branch_labels)
-    ]
+    milestone_revisions = []
+    for m in _get_revisions(script):
+        for branch_label in (m.branch_labels or [None]):
+            if milestone in getattr(m.module, 'neutron_milestone', []):
+                if branch is None or branch_label.endswith(branch):
+                    milestone_revisions.append((m.revision, branch))
+    return milestone_revisions
 
 
 def do_upgrade(config, cmd):
@@ -161,11 +164,11 @@ def do_upgrade(config, cmd):
 
     if CONF.command.expand:
         branch = EXPAND_BRANCH
-        revision = _get_branch_head(EXPAND_BRANCH)
+        revision = _get_branch_head(config, EXPAND_BRANCH)
 
     elif CONF.command.contract:
         branch = CONTRACT_BRANCH
-        revision = _get_branch_head(CONTRACT_BRANCH)
+        revision = _get_branch_head(config, CONTRACT_BRANCH)
 
     elif not CONF.command.revision and not CONF.command.delta:
         raise SystemExit(_('You must provide a revision or relative delta'))
@@ -217,14 +220,26 @@ def do_stamp(config, cmd):
                        sql=CONF.command.sql)
 
 
-def _get_branch_head(branch):
+def _get_branch_head(config, branch):
     '''Get the latest @head specification for a branch.'''
+    script_dir = alembic_script.ScriptDirectory.from_config(config)
+    revs = script_dir.revision_map.get_revisions('heads')
+    for rev in revs:
+        for branch_label in rev.branch_labels:
+            # For forwards and backwards compatibility we handle branch
+            # names of either
+            #    'contract/expand'
+            # or
+            #    'subproject-contract/subproject-expand'.
+            if branch_label.endswith(branch):
+                branch = branch_label
+                break
     return '%s@head' % branch
 
 
-def _check_bootstrap_new_branch(branch, version_path, addn_kwargs):
+def _check_bootstrap_new_branch(config, branch, version_path, addn_kwargs):
     addn_kwargs['version_path'] = version_path
-    addn_kwargs['head'] = _get_branch_head(branch)
+    addn_kwargs['head'] = _get_branch_head(config, branch)
     if not os.path.exists(version_path):
         # Bootstrap initial directory structure
         utils.ensure_dir(version_path)
@@ -251,7 +266,7 @@ def do_revision(config, cmd):
             args = copy.copy(kwargs)
             version_path = _get_version_branch_path(
                 config, release=CURRENT_RELEASE, branch=branch)
-            _check_bootstrap_new_branch(branch, version_path, args)
+            _check_bootstrap_new_branch(config, branch, version_path, args)
             do_alembic_command(config, cmd, **args)
     else:
         # autogeneration code will take care of enforcing proper directories
@@ -260,32 +275,15 @@ def do_revision(config, cmd):
     update_head_files(config)
 
 
-def _get_release_labels(labels):
-    result = set()
-    for label in labels:
-        # release labels were introduced Liberty for a short time and dropped
-        # in that same release cycle
-        result.add('%s_%s' % (migration.LIBERTY, label))
-    return result
-
-
 def _compare_labels(revision, expected_labels):
     # validate that the script has expected labels only
-    bad_labels = revision.branch_labels - expected_labels
+    expected_branch_labels = set()
+    for label in revision.branch_labels:
+        for expected_label in expected_labels:
+            if label.endswith(expected_label):
+                expected_branch_labels.add(label)
+    bad_labels = revision.branch_labels - expected_branch_labels
     if bad_labels:
-        # NOTE(ihrachyshka): this hack is temporary to accommodate those
-        # projects that already initialized their branches with liberty_*
-        # labels. Let's notify them about the deprecation for now and drop it
-        # later.
-        bad_labels_with_release = (revision.branch_labels -
-                                   _get_release_labels(expected_labels))
-        if not bad_labels_with_release:
-            alembic_util.warn(
-                _('Release aware branch labels (%s) are deprecated. '
-                  'Please switch to expand@ and contract@ '
-                  'labels.') % bad_labels)
-            return
-
         script_name = os.path.basename(revision.path)
         alembic_util.err(
             _('Unexpected label for script %(script_name)s: %(labels)s') %
@@ -339,6 +337,14 @@ def _get_revisions(script):
     return list(script.walk_revisions(base='base', head='heads'))
 
 
+def _get_branch_type(revision):
+    for branch_label in revision.branch_labels:
+        if branch_label.endswith(CONTRACT_BRANCH):
+            return CONTRACT_BRANCH
+        if branch_label.endswith(EXPAND_BRANCH):
+            return EXPAND_BRANCH
+
+
 def _get_branch_points(script):
     branchpoints = []
     for revision in _get_revisions(script):
@@ -352,10 +358,7 @@ def _get_heads_map(config):
     heads = script.get_heads()
     head_map = {}
     for head in heads:
-        if CONTRACT_BRANCH in script.get_revision(head).branch_labels:
-            head_map[CONTRACT_BRANCH] = head
-        else:
-            head_map[EXPAND_BRANCH] = head
+        head_map[_get_branch_type(script.get_revision(head))] = head
     return head_map
 
 

neutron/tests/functional/db/test_migrations.py

@@ -237,7 +237,12 @@ def find_migration_exceptions():
             script = alembic_script.ScriptDirectory.from_config(
                 self.alembic_config)
             for m in list(script.walk_revisions(base='base', head='heads')):
-                branches = m.branch_labels or []
+                branches = set()
+                for bl in m.branch_labels:
+                    if bl.endswith(migration.CONTRACT_BRANCH):
+                        branches.add(migration.CONTRACT_BRANCH)
+                    elif bl.endswith(migration.EXPAND_BRANCH):
+                        branches.add(migration.EXPAND_BRANCH)
                 if migration.CONTRACT_BRANCH in branches:
                     method_name = 'contract_creation_exceptions'
                     exceptions_dict = creation_exceptions