Delete shadow users when domain is deleted

Without this change, when an admin tries to delete an LDAP-backed
domain, it fails due to the foreign key relationship in the users table.
Previously, we were assuming that LDAP users existed solely in the LDAP
directory, but this is not true with shadow users. This patch fixes the
logic to delete the shadow users upon domain deletion.

Altered cherry-pick: use injected API provider since provider_api
mechanism doesn't exist in pike.

Change-Id: I12a08001e3aa08e4db9438cae425ad1a0a8070f7
Closes-bug: #1801873
(cherry picked from commit 1b16725d066f71a833ca74656c0c3dfe5f815e98)

3 files changed, 22 insertions, 9 deletions

diff --git a/keystone/identity/core.py b/keystone/identity/core.py
index 114c4a21c..fa0e0f729 100644
--- a/keystone/identity/core.py
+++ b/keystone/identity/core.py
@@ -502,14 +502,6 @@ class Manager(manager.Manager):
 
         driver = self._select_identity_driver(domain_id)
 
-        if not driver.is_sql:
-            # The LDAP driver does not support deleting users or groups.
-            # Moreover, we shouldn't destroy users and groups in an unknown
-            # driver. The only time when we should delete users and groups is
-            # when the backend is SQL because the foreign key in the SQL table
-            # forces us to.
-            return
-
         user_refs = self.list_users(domain_scope=domain_id)
         group_refs = self.list_groups(domain_scope=domain_id)
 
@@ -526,7 +518,10 @@ class Manager(manager.Manager):
         # And finally, delete the users themselves
         for user in user_refs:
             try:
-                self.delete_user(user['id'])
+                if not driver.is_sql:
+                    self.shadow_users_api.delete_user(user['id'])
+                else:
+                    self.delete_user(user['id'])
             except exception.UserNotFound:
                 LOG.debug(('User %(userid)s not found when deleting domain '
                            'contents for %(domainid)s, continuing with '
diff --git a/keystone/identity/shadow_backends/sql.py b/keystone/identity/shadow_backends/sql.py
index ccf420cbc..8f41c7116 100644
--- a/keystone/identity/shadow_backends/sql.py
+++ b/keystone/identity/shadow_backends/sql.py
@@ -16,6 +16,7 @@ import sqlalchemy
 import uuid
 
 from oslo_config import cfg
+from oslo_db import api as oslo_db_api
 
 from keystone.common import sql
 from keystone import exception
@@ -147,6 +148,17 @@ class ShadowUsers(base.ShadowUsersDriverBase):
             session.add(new_user_ref)
             return identity_base.filter_user(new_user_ref.to_dict())
 
+    @oslo_db_api.wrap_db_retry(retry_on_deadlock=True)
+    def delete_user(self, user_id):
+        with sql.session_for_write() as session:
+            ref = self._get_user(session, user_id)
+
+            q = session.query(model.UserGroupMembership)
+            q = q.filter_by(user_id=user_id)
+            q.delete(False)
+
+            session.delete(ref)
+
     def get_user(self, user_id):
         with sql.session_for_read() as session:
             user_ref = self._get_user(session, user_id)
diff --git a/releasenotes/notes/bug-1801873-0eb9a5ec3e801190.yaml b/releasenotes/notes/bug-1801873-0eb9a5ec3e801190.yaml
new file mode 100644
index 000000000..7fd970d35
--- /dev/null
+++ b/releasenotes/notes/bug-1801873-0eb9a5ec3e801190.yaml
@@ -0,0 +1,6 @@
+---
+fixes:
+  - |
+    [`bug 1801873 <https://bugs.launchpad.net/keystone/+bug/1801873>`_]
+    This fixes an issue where an LDAP-backed domain could not be deleted due to
+    the existence of shadow users in the SQL database.