Using same config with primary for replicas

Change-Id: Icadc95ea54e4509dc148f8e84f2eaac5840509f3

11 files changed, 278 insertions, 266 deletions

diff --git a/doc/source/user/backup-db.rst b/doc/source/user/backup-db.rst
index 35bb8782..9a1a10e5 100644
--- a/doc/source/user/backup-db.rst
+++ b/doc/source/user/backup-db.rst
@@ -143,7 +143,7 @@ instance from the backup.
 
    .. code-block:: console
 
-      $ openstack database instance create guest2 10 --size 2 --nic net-id=$network_id --backup BACKUP_ID
+      $ openstack database instance create guest2 --flavor 10 --size 2 --nic net-id=$network_id --backup BACKUP_ID
       +-------------------+----------------------------------------------+
       |      Property     |                Value                         |
       +-------------------+----------------------------------------------+
diff --git a/doc/source/user/create-db.rst b/doc/source/user/create-db.rst
index d43ee650..b8446b84 100644
--- a/doc/source/user/create-db.rst
+++ b/doc/source/user/create-db.rst
@@ -107,7 +107,7 @@ Create and access a database
    .. code-block:: console
 
       $ openstack database instance create mysql_instance_1 \
-          6 \
+          --flavor 6 \
           --size 5 \
           --nic net-id=8799cf10-01ef-40e2-b04e-06da7cfa5668 \
           --databases test --users userA:password \
diff --git a/doc/source/user/set-up-replication.rst b/doc/source/user/set-up-replication.rst
index 6ec3c16b..6528ea87 100644
--- a/doc/source/user/set-up-replication.rst
+++ b/doc/source/user/set-up-replication.rst
@@ -2,109 +2,164 @@
 Set up database replication
 ===========================
 
-You can create a replica of an existing database instance. When you make
-subsequent changes to the original instance, the system automatically
-applies those changes to the replica.
+You can create replicas of an existing database instance(the primary) to
+improve the performance and scale of read-intensive workloads. Read workloads
+can be isolated to the replicas, while write workloads can be directed to the
+primary. When you make subsequent changes to the primary, the system
+automatically applies those changes to the replicas. Because replicas are
+read-only, they don't directly reduce write-capacity burdens on the primary.
+This feature isn't targeted at write-intensive workloads.
 
--  Replicas are read-only.
+- Not all the datastores support replication feature in Trove.
 
--  When you create a replica, do not specify the ``--users`` or
-   ``--databases`` options.
+- A replica is created by using the same server configuration as the primary,
+  e.g. flavor, data volume, datastore, etc. After a replica is created, several
+  settings can be changed independently from the primary server, e.g. the data
+  volume size.
 
--  You can choose a smaller volume or flavor for a replica than for the
-   original, but the replica's volume must be big enough to hold the
-   data snapshot from the original.
+- Currently, There is no automated failover between primary and replicas.
 
-This example shows you how to replicate a MySQL database instance.
+- Trove can only create a new replica. Adding an already existing instance to
+  the replication group is not supported.
+
+- Creating a replica of a replica is not supported.
+
+- When deleting replication instances, replicas need to be removed before the
+  primary.
 
 Set up replication
-~~~~~~~~~~~~~~~~~~
+------------------
 
-#. **Get the instance ID**
+#. Create a replica
 
-   Get the ID of the original instance you want to replicate:
+   First, make sure you have an instance (ID:
+   cebbf187-e223-46dd-8802-6dc04e895d0a) up and running in HEALTHY status,
+   create a replica:
 
    .. code-block:: console
 
-      $ openstack database instance list
-      +-----------+------------+-----------+-------------------+--------+-----------+------+
-      |     id    |  name      | datastore | datastore_version | status | flavor_id | size |
-      +-----------+------------+-----------+-------------------+--------+-----------+------+
-      | 97b...ae6 | base_1     |   mysql   |     mysql-5.5     | ACTIVE |     10    |  2   |
-      +-----------+------------+-----------+-------------------+--------+-----------+------+
+      $ openstack database instance create test-mysql-replica-1 \
+          --nic net-id=$netid \
+          --replica_of cebbf187-e223-46dd-8802-6dc04e895d0a
+
+#. Wait for the replica instance successfully created, verify status of the
+   replication servers.
+
+   .. code-block:: console
 
-#. **Create the replica**
+      $ odbi list
+      +--------------------------------------+----------------------+-----------+-------------------+---------+------------------------------------------------+-----------+------+-----------+---------+
+      | ID                                   | Name                 | Datastore | Datastore Version | Status  | Addresses                                      | Flavor ID | Size | Region    | Role    |
+      +--------------------------------------+----------------------+-----------+-------------------+---------+------------------------------------------------+-----------+------+-----------+---------+
+      | 71f30a72-4e47-4505-9e7f-ffd8933a331c | test-mysql-replica-1 | mysql     | 5.7.29            | HEALTHY | [{'address': '10.1.0.155', 'type': 'private'}] | d2        |    2 | RegionOne | replica |
+      | cebbf187-e223-46dd-8802-6dc04e895d0a | test-mysql           | mysql     | 5.7.29            | HEALTHY | [{'address': '10.1.0.43', 'type': 'private'}]  | d2        |    2 | RegionOne | primary |
+      +--------------------------------------+----------------------+-----------+-------------------+---------+------------------------------------------------+-----------+------+-----------+---------+
 
-   Create a new instance that will be a replica of the original
-   instance. You do this by passing in the ``--replica_of`` option with
-   the :command:`openstack database instance create` command. This example creates a replica
-   called ``replica_1``. ``replica_1`` is a replica of the original instance,
-   ``base_1``:
+#. Verify replication status.
+
+   Replication can be verified by making some modifications to the primary and
+   ensuring that the modifications also propagate back to the replica. We will
+   create a database called "newdb" on the primary and check it's automatically
+   created on the replica.
+
+   First, get the existing databases of primary and replica, they should be the
+   same:
 
    .. code-block:: console
 
-      $ openstack database instance create replica_1 6 --size=5 --nic net-id=$netid \
-        --datastore_version mysql-5.5 \
-        --datastore mysql --replica_of ID_OF_ORIGINAL_INSTANCE
+      $ openstack database db list cebbf187-e223-46dd-8802-6dc04e895d0a # The primary
+      +--------+
+      | Name   |
+      +--------+
+      | testdb |
+      +--------+
+      $ openstack database db list 71f30a72-4e47-4505-9e7f-ffd8933a331c # The replica
+      +--------+
+      | Name   |
+      +--------+
+      | testdb |
+      +--------+
+
+   Create a new database on the primary:
+
+   .. code-block:: console
 
-#. **Verify replication status**
+      $ openstack database db create cebbf187-e223-46dd-8802-6dc04e895d0a newdb
 
-   Pass in ``replica_1``'s instance ID with the :command:`openstack database instance show` command
-   to verify that the newly created ``replica_1`` instance is a replica
-   of the original ``base_1``. Note that the ``replica_of`` property is
-   set to the ID of ``base_1``.
+   Check the new database is also created on the replica:
 
    .. code-block:: console
 
-      $ openstack database instance show INSTANCE_ID_OF_REPLICA_1
-      +-------------------+--------------------------------------+
-      | Property          | Value                                |
-      +-------------------+--------------------------------------+
-      | created           | 2014-09-16T11:16:49                  |
-      | datastore         | mysql                                |
-      | datastore_version | mysql-5.5                            |
-      | flavor            | 6                                    |
-      | id                | 49c6eff6-ef91-4eff-91c0-efbda7e83c38 |
-      | name              | replica_1                            |
-      | replica_of        | 97b4b853-80f6-414f-ba6f-c6f455a79ae6 |
-      | status            | BUILD                                |
-      | updated           | 2014-09-16T11:16:49                  |
-      | volume            | 5                                    |
-      +-------------------+--------------------------------------+
-
-   Now pass in ``base_1``'s instance ID with the :command:`openstack database instance show` command
-   to list the replica(s) associated with the original instance. Note
-   that the ``replicas`` property is set to the ID of ``replica_1``. If
-   there are multiple replicas, they appear as a comma-separated list.
+      $ openstack database db list 71f30a72-4e47-4505-9e7f-ffd8933a331c
+      +--------+
+      | Name   |
+      +--------+
+      | newdb  |
+      | testdb |
+      +--------+
+
+Failover
+--------
+
+Since replication is asynchronous, there is lag between the primary and the
+replica. The amount of lag can be influenced by a number of factors like how
+heavy the workload running on the primary server is and the latency between
+data centers. In most cases, replica lag ranges between a few seconds to a
+couple minutes.
+
+#. Before performing failover, we will create one more replica:
+
+   .. code-block:: console
+
+      $ openstack database instance create test-mysql-replica-2 \
+          --nic net-id=$netid \
+          --replica_of cebbf187-e223-46dd-8802-6dc04e895d0a
+
+   Now we have 3 instances running in a replication group:
 
    .. code-block:: console
 
-      $ openstack database instance show INSTANCE_ID_OF_BASE_1
-      +-------------------+--------------------------------------+
-      | Property          | Value                                |
-      +-------------------+--------------------------------------+
-      | created           | 2014-09-16T11:04:56                  |
-      | datastore         | mysql                                |
-      | datastore_version | mysql-5.5                            |
-      | flavor            | 6                                    |
-      | id                | 97b4b853-80f6-414f-ba6f-c6f455a79ae6 |
-      | ip                | 172.16.200.2                         |
-      | name              | base_1                               |
-      | replicas          | 49c6eff6-ef91-4eff-91c0-efbda7e83c38 |
-      | status            | ACTIVE                               |
-      | updated           | 2014-09-16T11:05:06                  |
-      | volume            | 5                                    |
-      | volume_used       | 0.11                                 |
-      +-------------------+--------------------------------------+
-
-#. **Detach the replica**
-
-   If the original instance goes down, you can detach the replica. The
-   replica becomes a standalone database instance. You can then take the
-   new standalone instance and create a new replica of that instance.
-
-   You detach a replica using the :command:`openstack database instance detach replica` command:
+      $ odbi list
+      +--------------------------------------+----------------------+-----------+-------------------+---------+------------------------------------------------+-----------+------+-----------+---------+
+      | ID                                   | Name                 | Datastore | Datastore Version | Status  | Addresses                                      | Flavor ID | Size | Region    | Role    |
+      +--------------------------------------+----------------------+-----------+-------------------+---------+------------------------------------------------+-----------+------+-----------+---------+
+      | 71f30a72-4e47-4505-9e7f-ffd8933a331c | test-mysql-replica-1 | mysql     | 5.7.29            | HEALTHY | [{'address': '10.1.0.155', 'type': 'private'}] | d2        |    2 | RegionOne | replica |
+      | a85ece86-9f62-4aa8-bb15-eba604cd2a01 | test-mysql-replica-2 | mysql     | 5.7.29            | HEALTHY | [{'address': '10.1.0.243', 'type': 'private'}] | d2        |    2 | RegionOne | replica |
+      | cebbf187-e223-46dd-8802-6dc04e895d0a | test-mysql           | mysql     | 5.7.29            | HEALTHY | [{'address': '10.1.0.43', 'type': 'private'}]  | d2        |    2 | RegionOne | primary |
+      +--------------------------------------+----------------------+-----------+-------------------+---------+------------------------------------------------+-----------+------+-----------+---------+
+
+#. Failover(promote) "test-mysql-replica-1" to primary.
 
    .. code-block:: console
 
-      $ openstack database instance detach replica INSTANCE_ID_OF_REPLICA
+      $ openstack database instance promote 71f30a72-4e47-4505-9e7f-ffd8933a331c
+
+   Wait for Trove setting up the new replication, the status of the 3 instances become "PROMOTE" then "HEALTHY".
+
+   .. code-block:: console
+
+      $ openstack database instance list
+      +--------------------------------------+----------------------+-----------+-------------------+---------+------------------------------------------------+-----------+------+-----------+---------+
+      | ID                                   | Name                 | Datastore | Datastore Version | Status  | Addresses                                      | Flavor ID | Size | Region    | Role    |
+      +--------------------------------------+----------------------+-----------+-------------------+---------+------------------------------------------------+-----------+------+-----------+---------+
+      | 71f30a72-4e47-4505-9e7f-ffd8933a331c | test-mysql-replica-1 | mysql     | 5.7.29            | HEALTHY | [{'address': '10.1.0.155', 'type': 'private'}] | d2        |    2 | RegionOne | primary |
+      | a85ece86-9f62-4aa8-bb15-eba604cd2a01 | test-mysql-replica-2 | mysql     | 5.7.29            | HEALTHY | [{'address': '10.1.0.243', 'type': 'private'}] | d2        |    2 | RegionOne | replica |
+      | cebbf187-e223-46dd-8802-6dc04e895d0a | test-mysql           | mysql     | 5.7.29            | HEALTHY | [{'address': '10.1.0.43', 'type': 'private'}]  | d2        |    2 | RegionOne | replica |
+      +--------------------------------------+----------------------+-----------+-------------------+---------+------------------------------------------------+-----------+------+-----------+---------+
+
+#. Point your application to the (former) replica.
+
+   Each server has a unique connection string. Update your application to point
+   to the (former) replica instead of the primary.
+
+Other supported operations
+--------------------------
+
+* Remove a failed primary. This essentially is used to eject an already failed
+  primary in order to establish a new one between the replicas. Command:
+  ``openstack database instance eject <primary_ID>``
+
+* Change replica to a standalone database server. The detached replica becomes
+  a standalone server that accepts both reads and writes. The standalone server
+  can't be made into a replica again.. Command:
+  ``openstack database instance detach <replica_ID>``
\ No newline at end of file
diff --git a/doc/source/user/upgrade-datastore.rst b/doc/source/user/upgrade-datastore.rst
index 3947b37c..4fb8dccc 100644
--- a/doc/source/user/upgrade-datastore.rst
+++ b/doc/source/user/upgrade-datastore.rst
@@ -49,7 +49,7 @@ Upgrading datastore
    .. code-block:: console
 
       $ openstack database instance create test-mysql-upgrade \
-        d2 \
+        --flavor d2 \
         --size 1 \
         --nic net-id=$netid \
         --datastore mysql --datastore_version 5.7.29 \
diff --git a/trove/common/apischema.py b/trove/common/apischema.py
index 0e3d60b1..0388face 100644
--- a/trove/common/apischema.py
+++ b/trove/common/apischema.py
@@ -381,7 +381,7 @@ instance = {
         "properties": {
             "instance": {
                 "type": "object",
-                "required": ["name", "flavorRef"],
+                "required": ["name"],
                 "additionalProperties": True,
                 "properties": {
                     "name": non_empty_string,
@@ -398,6 +398,12 @@ instance = {
                             "backupRef": uuid
                         }
                     },
+                    "replica_of": uuid,
+                    "replica_count": {
+                        "type": "integer",
+                        "minimum": 1,
+                        "maximum": 3
+                    },
                     "availability_zone": non_empty_string,
                     "datastore": {
                         "type": "object",
diff --git a/trove/instance/models.py b/trove/instance/models.py
index 47b4c72c..daa8d3bf 100644
--- a/trove/instance/models.py
+++ b/trove/instance/models.py
@@ -1059,8 +1059,10 @@ class Instance(BuiltInstance):
                configuration_id=None, slave_of_id=None, cluster_config=None,
                replica_count=None, volume_type=None, modules=None,
                locality=None, region_name=None, access=None):
-
-        region_name = region_name or CONF.service_credentials.region_name
+        nova_client = clients.create_nova_client(context)
+        cinder_client = clients.create_cinder_client(context)
+        datastore_cfg = CONF.get(datastore_version.manager)
+        volume_support = datastore_cfg.volume_support
 
         call_args = {
             'name': name,
@@ -1070,7 +1072,10 @@ class Instance(BuiltInstance):
             'image_id': image_id,
             'availability_zone': availability_zone,
             'region_name': region_name,
+            'locality': locality
         }
+        if cluster_config:
+            call_args['cluster_id'] = cluster_config.get("id", None)
 
         # All nova flavors are permitted for a datastore-version unless one
         # or more entries are found in datastore_version_metadata,
@@ -1086,14 +1091,16 @@ class Instance(BuiltInstance):
                     datastore=datastore.name,
                     datastore_version=datastore_version.name,
                     flavor_id=flavor_id)
-
-        datastore_cfg = CONF.get(datastore_version.manager)
-        client = clients.create_nova_client(context)
         try:
-            flavor = client.flavors.get(flavor_id)
+            flavor = nova_client.flavors.get(flavor_id)
         except nova_exceptions.NotFound:
             raise exception.FlavorNotFound(uuid=flavor_id)
 
+        replica_source = None
+        if slave_of_id:
+            replica_source = DBInstance.find_by(
+                context, id=slave_of_id, deleted=False)
+
         # If a different region is specified for the instance, ensure
         # that the flavor and image are the same in both regions
         if region_name and region_name != CONF.service_credentials.region_name:
@@ -1101,13 +1108,23 @@ class Instance(BuiltInstance):
                                            datastore, datastore_version)
 
         deltas = {'instances': 1}
-        volume_support = datastore_cfg.volume_support
         if volume_support:
-            call_args['volume_type'] = volume_type
+            if replica_source:
+                try:
+                    volume = cinder_client.volumes.get(
+                        replica_source.volume_id)
+                except Exception as e:
+                    LOG.error(f'Failed to get volume from Cinder, error: '
+                              f'{str(e)}')
+                    raise exception.NotFound(uuid=replica_source.volume_id)
+                volume_type = volume.volume_type
+                volume_size = volume.size
+
             dvm.validate_volume_type(context, volume_type,
                                      datastore.name, datastore_version.name)
-            call_args['volume_size'] = volume_size
             validate_volume_size(volume_size)
+            call_args['volume_type'] = volume_type
+            call_args['volume_size'] = volume_size
             deltas['volumes'] = volume_size
             # Instance volume should have enough space for the backup
             # Backup, and volume sizes are in GBs
@@ -1147,60 +1164,36 @@ class Instance(BuiltInstance):
                     datastore2=datastore.name)
 
         if slave_of_id:
-            Backup.verify_swift_auth_token(context)
-
-            if databases or users:
-                raise exception.ReplicaCreateWithUsersDatabasesError()
             call_args['replica_of'] = slave_of_id
             call_args['replica_count'] = replica_count
+
             replication_support = datastore_cfg.replication_strategy
             if not replication_support:
                 raise exception.ReplicationNotSupported(
                     datastore=datastore.name)
-            try:
-                # looking for replica source
-                replica_source = DBInstance.find_by(
-                    context,
-                    id=slave_of_id,
-                    deleted=False)
-                if replica_source.slave_of_id:
-                    raise exception.Forbidden(
-                        _("Cannot create a replica of a replica %(id)s.")
-                        % {'id': slave_of_id})
-                if (CONF.verify_replica_volume_size
-                        and replica_source.volume_size > volume_size):
-                    raise exception.Forbidden(
-                        _("Replica volume size should not be smaller than"
-                          " master's, replica volume size: %(replica_size)s"
-                          " and master volume size: %(master_size)s.")
-                        % {'replica_size': volume_size,
-                           'master_size': replica_source.volume_size})
-                # load the replica source status to check if
-                # source is available
-                load_simple_instance_server_status(
+            if (CONF.verify_replica_volume_size
+                    and replica_source.volume_size > volume_size):
+                raise exception.Forbidden(
+                    _("Replica volume size should not be smaller than"
+                      " master's, replica volume size: %(replica_size)s"
+                      " and master volume size: %(master_size)s.")
+                    % {'replica_size': volume_size,
+                       'master_size': replica_source.volume_size})
+            # load the replica source status to check if
+            # source is available
+            load_simple_instance_server_status(
+                context,
+                replica_source)
+            replica_source_instance = Instance(
+                context, replica_source,
+                None,
+                InstanceServiceStatus.find_by(
                     context,
-                    replica_source)
-                replica_source_instance = Instance(
-                    context, replica_source,
-                    None,
-                    InstanceServiceStatus.find_by(
-                        context,
-                        instance_id=slave_of_id))
-                replica_source_instance.validate_can_perform_action()
-            except exception.ModelNotFoundError:
-                LOG.exception(
-                    "Cannot create a replica of %(id)s "
-                    "as that instance could not be found.",
-                    {'id': slave_of_id})
-                raise exception.NotFound(uuid=slave_of_id)
-        elif replica_count and replica_count != 1:
-            raise exception.Forbidden(_(
-                "Replica count only valid when creating replicas. Cannot "
-                "create %(count)d instances.") % {'count': replica_count})
+                    instance_id=slave_of_id))
+            replica_source_instance.validate_can_perform_action()
+
         multi_replica = slave_of_id and replica_count and replica_count > 1
         instance_count = replica_count if multi_replica else 1
-        if locality:
-            call_args['locality'] = locality
 
         if not nics:
             nics = []
@@ -1211,8 +1204,6 @@ class Instance(BuiltInstance):
                            for net_id in CONF.management_networks]
         if nics:
             call_args['nics'] = nics
-        if cluster_config:
-            call_args['cluster_id'] = cluster_config.get("id", None)
 
         if not modules:
             modules = []
@@ -1228,7 +1219,6 @@ class Instance(BuiltInstance):
         module_list = module_views.convert_modules_to_list(modules)
 
         def _create_resources():
-
             if cluster_config:
                 cluster_id = cluster_config.get("id", None)
                 shard_id = cluster_config.get("shard_id", None)
@@ -1251,17 +1241,15 @@ class Instance(BuiltInstance):
                     slave_of_id=slave_of_id, cluster_id=cluster_id,
                     shard_id=shard_id, type=instance_type,
                     region_id=region_name)
-                LOG.debug("Tenant %(tenant)s created new Trove instance "
-                          "%(db)s in region %(region)s.",
-                          {'tenant': context.project_id, 'db': db_info.id,
-                           'region': region_name})
-
                 instance_id = db_info.id
-                cls.add_instance_modules(context, instance_id, modules)
                 instance_name = name
+                LOG.debug(f"Creating new instance {instance_id}")
                 ids.append(instance_id)
                 names.append(instance_name)
                 root_passwords.append(None)
+
+                cls.add_instance_modules(context, instance_id, modules)
+
                 # change the name to be name + replica_number if more than one
                 if multi_replica:
                     replica_number = instance_index + 1
@@ -1272,9 +1260,9 @@ class Instance(BuiltInstance):
                 # if a configuration group is associated with an instance,
                 # generate an overrides dict to pass into the instance creation
                 # method
-
                 config = Configuration(context, configuration_id)
                 overrides = config.get_configuration_overrides()
+
                 service_status = InstanceServiceStatus.create(
                     instance_id=instance_id,
                     status=srvstatus.ServiceStatuses.NEW)
diff --git a/trove/instance/service.py b/trove/instance/service.py
index 17de296e..8542b024 100644
--- a/trove/instance/service.py
+++ b/trove/instance/service.py
@@ -32,7 +32,7 @@ from trove.common import pagination
 from trove.common import policy
 from trove.common import utils
 from trove.common import wsgi
-from trove.datastore import models as datastore_models
+from trove.datastore import models as ds_models
 from trove.extensions.mysql.common import populate_users
 from trove.extensions.mysql.common import populate_validated_databases
 from trove.instance import models, views
@@ -341,24 +341,81 @@ class InstanceController(wsgi.Controller):
                     raise exception.NetworkConflict()
 
     def create(self, req, body, tenant_id):
-        # TODO(hub-cap): turn this into middleware
         LOG.info("Creating a database instance for tenant '%s'",
                  tenant_id)
         LOG.debug("req : '%s'\n\n", strutils.mask_password(req))
         LOG.debug("body : '%s'\n\n", strutils.mask_password(body))
         context = req.environ[wsgi.CONTEXT_KEY]
         policy.authorize_on_tenant(context, 'instance:create')
-        context.notification = notification.DBaaSInstanceCreate(context,
-                                                                request=req)
-        datastore_args = body['instance'].get('datastore', {})
-        datastore, datastore_version = (
-            datastore_models.get_datastore_version(**datastore_args))
-        image_id = datastore_version.image_id
+        context.notification = notification.DBaaSInstanceCreate(
+            context, request=req)
+
         name = body['instance']['name']
-        flavor_ref = body['instance']['flavorRef']
+        slave_of_id = body['instance'].get('replica_of')
+        replica_count = body['instance'].get('replica_count')
+        flavor_ref = body['instance'].get('flavorRef')
+        datastore_args = body['instance'].get('datastore', {})
+        volume_info = body['instance'].get('volume', {})
+        availability_zone = body['instance'].get('availability_zone')
+        nics = body['instance'].get('nics', [])
+        locality = body['instance'].get('locality')
+        region_name = body['instance'].get(
+            'region_name', CONF.service_credentials.region_name
+        )
+        access = body['instance'].get('access', None)
+
+        if slave_of_id:
+            if flavor_ref:
+                msg = 'Cannot specify flavor when creating replicas.'
+                raise exception.BadRequest(message=msg)
+            if datastore_args:
+                msg = 'Cannot specify datastore when creating replicas.'
+                raise exception.BadRequest(message=msg)
+            if volume_info:
+                msg = 'Cannot specify volume when creating replicas.'
+                raise exception.BadRequest(message=msg)
+            if locality:
+                msg = 'Cannot specify locality when creating replicas.'
+                raise exception.BadRequest(message=msg)
+            backup_model.verify_swift_auth_token(context)
+        else:
+            if replica_count and replica_count > 1:
+                msg = (f"Replica count only valid when creating replicas. "
+                       f"Cannot create {replica_count} instances.")
+                raise exception.BadRequest(message=msg)
+
         flavor_id = utils.get_id_from_href(flavor_ref)
 
-        configuration = self._configuration_parse(context, body)
+        if volume_info:
+            volume_size = int(volume_info.get('size'))
+            volume_type = volume_info.get('type')
+        else:
+            volume_size = None
+            volume_type = None
+
+        if slave_of_id:
+            try:
+                replica_source = models.DBInstance.find_by(
+                    context, id=slave_of_id, deleted=False)
+                flavor_id = replica_source.flavor_id
+            except exception.ModelNotFoundError:
+                LOG.error(f"Cannot create a replica of {slave_of_id} as that "
+                          f"instance could not be found.")
+                raise exception.NotFound(uuid=slave_of_id)
+            if replica_source.slave_of_id:
+                raise exception.Forbidden(
+                    f"Cannot create a replica of a replica {slave_of_id}")
+
+            datastore_version = ds_models.DatastoreVersion.load_by_uuid(
+                replica_source.datastore_version_id)
+            datastore = ds_models.Datastore.load(
+                datastore_version.datastore_id)
+        else:
+            datastore, datastore_version = ds_models.get_datastore_version(
+                **datastore_args)
+
+        image_id = datastore_version.image_id
+
         databases = populate_validated_databases(
             body['instance'].get('databases', []))
         database_names = [database.get('_name', '') for database in databases]
@@ -368,7 +425,10 @@ class InstanceController(wsgi.Controller):
                                    database_names)
         except ValueError as ve:
             raise exception.BadRequest(message=ve)
+        if slave_of_id and (databases or users):
+            raise exception.ReplicaCreateWithUsersDatabasesError()
 
+        configuration = self._configuration_parse(context, body)
         modules = body['instance'].get('modules')
 
         # The following operations have their own API calls.
@@ -388,34 +448,22 @@ class InstanceController(wsgi.Controller):
             policy.authorize_on_tenant(
                 context, 'instance:extension:database:create')
 
-        if 'volume' in body['instance']:
-            volume_info = body['instance']['volume']
-            volume_size = int(volume_info['size'])
-            volume_type = volume_info.get('type')
-        else:
-            volume_size = None
-            volume_type = None
-
         if 'restorePoint' in body['instance']:
             backupRef = body['instance']['restorePoint']['backupRef']
             backup_id = utils.get_id_from_href(backupRef)
         else:
             backup_id = None
 
-        availability_zone = body['instance'].get('availability_zone')
-
         # Only 1 nic is allowed as defined in API jsonschema.
-        # Use list here just for backward compatibility.
-        nics = body['instance'].get('nics', [])
+        # Use list just for backward compatibility.
         if len(nics) > 0:
-            LOG.info('Checking user provided instance network %s', nics[0])
-            self._check_nic(context, nics[0])
+            nic = nics[0]
+            LOG.info('Checking user provided instance network %s', nic)
+            if slave_of_id and nic.get('ip_address'):
+                msg = "Cannot specify IP address when creating replicas."
+                raise exception.BadRequest(message=msg)
+            self._check_nic(context, nic)
 
-        slave_of_id = body['instance'].get('replica_of',
-                                           # also check for older name
-                                           body['instance'].get('slave_of'))
-        replica_count = body['instance'].get('replica_count')
-        locality = body['instance'].get('locality')
         if locality:
             locality_domain = ['affinity', 'anti-affinity']
             locality_domain_msg = ("Invalid locality '%s'. "
@@ -424,16 +472,6 @@ class InstanceController(wsgi.Controller):
                                     "', '".join(locality_domain)))
             if locality not in locality_domain:
                 raise exception.BadRequest(message=locality_domain_msg)
-            if slave_of_id:
-                dupe_locality_msg = (
-                    'Cannot specify locality when adding replicas to existing '
-                    'master.')
-                raise exception.BadRequest(message=dupe_locality_msg)
-
-        region_name = body['instance'].get(
-            'region_name', CONF.service_credentials.region_name
-        )
-        access = body['instance'].get('access', None)
 
         instance = models.Instance.create(context, name, flavor_id,
                                           image_id, databases, users,
@@ -480,7 +518,7 @@ class InstanceController(wsgi.Controller):
                 with StartNotification(context, instance_id=instance.id):
                     instance.detach_configuration()
         if 'datastore_version' in kwargs:
-            datastore_version = datastore_models.DatastoreVersion.load(
+            datastore_version = ds_models.DatastoreVersion.load(
                 instance.datastore, kwargs['datastore_version'])
             context.notification = (
                 notification.DBaaSInstanceUpgrade(context, request=req))
diff --git a/trove/taskmanager/manager.py b/trove/taskmanager/manager.py
index bbec7d0b..01eaa741 100644
--- a/trove/taskmanager/manager.py
+++ b/trove/taskmanager/manager.py
@@ -359,8 +359,8 @@ class Manager(periodic_task.PeriodicTasks):
         try:
             for replica_index in range(0, len(ids)):
                 replica_number += 1
-                LOG.info("Creating replica %(num)d of %(count)d.",
-                         {'num': replica_number, 'count': len(ids)})
+                LOG.info(f"Creating replica {replica_number} "
+                         f"({ids[replica_index]}) of {len(ids)}.")
 
                 instance_tasks = FreshInstanceTasks.load(
                     context, ids[replica_index])
diff --git a/trove/tests/api/replication.py b/trove/tests/api/replication.py
index 4dd49307..0d4e341a 100644
--- a/trove/tests/api/replication.py
+++ b/trove/tests/api/replication.py
@@ -108,10 +108,6 @@ def instance_is_active(id):
 def create_slave():
     result = instance_info.dbaas.instances.create(
         instance_info.name + "_slave",
-        instance_info.dbaas_flavor_href,
-        {'size': 2},
-        datastore=instance_info.dbaas_datastore,
-        datastore_version=instance_info.dbaas_datastore_version,
         nics=instance_info.nics,
         replica_of=instance_info.id)
     assert_equal(200, instance_info.dbaas.last_http_code)
@@ -141,20 +137,6 @@ def validate_master(master, slaves):
       groups=[tests.DBAAS_API_REPLICATION],
       enabled=CONFIG.swift_enabled)
 class CreateReplicationSlave(object):
-
-    @test
-    def test_replica_provisioning_with_missing_replica_source(self):
-        assert_raises(exceptions.NotFound,
-                      instance_info.dbaas.instances.create,
-                      instance_info.name + "_slave",
-                      instance_info.dbaas_flavor_href,
-                      instance_info.volume,
-                      datastore=instance_info.dbaas_datastore,
-                      datastore_version=instance_info.dbaas_datastore_version,
-                      nics=instance_info.nics,
-                      replica_of="Missing replica source")
-        assert_equal(404, instance_info.dbaas.last_http_code)
-
     @test
     def test_create_db_on_master(self):
         """test_create_db_on_master"""
diff --git a/trove/tests/scenario/runners/replication_runners.py b/trove/tests/scenario/runners/replication_runners.py
index a9115fed..2d862ebd 100644
--- a/trove/tests/scenario/runners/replication_runners.py
+++ b/trove/tests/scenario/runners/replication_runners.py
@@ -88,10 +88,7 @@ class ReplicationRunner(TestRunner):
         client = self.auth_client
         client.instances.create(
             self.instance_info.name + '_' + replica_name,
-            self.instance_info.dbaas_flavor_href,
-            self.instance_info.volume, replica_of=master_id,
-            datastore=self.instance_info.dbaas_datastore,
-            datastore_version=self.instance_info.dbaas_datastore_version,
+            replica_of=master_id,
             nics=self.instance_info.nics,
             replica_count=replica_count)
         self.assert_client_code(client, expected_http_code)
@@ -154,10 +151,6 @@ class ReplicationRunner(TestRunner):
         client = self.auth_client
         self.non_affinity_repl_id = client.instances.create(
             self.instance_info.name + '_non-affinity-repl',
-            self.instance_info.dbaas_flavor_href,
-            self.instance_info.volume,
-            datastore=self.instance_info.dbaas_datastore,
-            datastore_version=self.instance_info.dbaas_datastore_version,
             nics=self.instance_info.nics,
             replica_of=self.non_affinity_master_id,
             replica_count=1).id
diff --git a/trove/tests/unittests/instance/test_instance_models.py b/trove/tests/unittests/instance/test_instance_models.py
index f63314b5..10befc8c 100644
--- a/trove/tests/unittests/instance/test_instance_models.py
+++ b/trove/tests/unittests/instance/test_instance_models.py
@@ -343,6 +343,7 @@ class TestReplication(trove_testtools.TestCase):
             id=str(uuid.uuid4()),
             name="TestMasterInstance",
             datastore_version_id=self.datastore_version.id,
+            flavor_id=str(uuid.uuid4()),
             volume_size=2)
         self.master.set_task_status(InstanceTasks.NONE)
         self.master.save()
@@ -371,18 +372,6 @@ class TestReplication(trove_testtools.TestCase):
         super(TestReplication, self).tearDown()
 
     @patch('trove.instance.models.LOG')
-    def test_replica_of_not_active_master(self, mock_logging):
-        self.master.set_task_status(InstanceTasks.BUILDING)
-        self.master.save()
-        self.master_status.set_status(ServiceStatuses.BUILDING)
-        self.master_status.save()
-        self.assertRaises(exception.UnprocessableEntity,
-                          Instance.create,
-                          None, 'name', 1, "UUID", [], [], self.datastore,
-                          self.datastore_version, 2,
-                          None, slave_of_id=self.master.id)
-
-    @patch('trove.instance.models.LOG')
     def test_replica_with_invalid_slave_of_id(self, mock_logging):
         self.assertRaises(exception.NotFound,
                           Instance.create,
@@ -390,45 +379,6 @@ class TestReplication(trove_testtools.TestCase):
                           self.datastore_version, 2,
                           None, slave_of_id=str(uuid.uuid4()))
 
-    def test_create_replica_from_replica(self):
-        self.replica_datastore_version = Mock(
-            spec=datastore_models.DBDatastoreVersion)
-        self.replica_datastore_version.id = "UUID"
-        self.replica_datastore_version.manager = 'mysql'
-        self.replica_info = DBInstance(
-            InstanceTasks.NONE,
-            id="UUID",
-            name="TestInstance",
-            datastore_version_id=self.replica_datastore_version.id,
-            slave_of_id=self.master.id)
-        self.replica_info.save()
-        self.assertRaises(exception.Forbidden, Instance.create,
-                          None, 'name', 2, "UUID", [], [], self.datastore,
-                          self.datastore_version, 2,
-                          None, slave_of_id=self.replica_info.id)
-
-    def test_create_replica_with_users(self):
-        self.users.append({"name": "testuser", "password": "123456"})
-        self.assertRaises(exception.ReplicaCreateWithUsersDatabasesError,
-                          Instance.create, None, 'name', 2, "UUID", [],
-                          self.users, self.datastore, self.datastore_version,
-                          1, None, slave_of_id=self.master.id)
-
-    def test_create_replica_with_databases(self):
-        self.databases.append({"name": "testdb"})
-        self.assertRaises(exception.ReplicaCreateWithUsersDatabasesError,
-                          Instance.create, None, 'name', 1, "UUID",
-                          self.databases, [], self.datastore,
-                          self.datastore_version, 2, None,
-                          slave_of_id=self.master.id)
-
-    def test_replica_volume_size_smaller_than_master(self):
-        self.assertRaises(exception.Forbidden,
-                          Instance.create,
-                          None, 'name', 1, "UUID", [], [], self.datastore,
-                          self.datastore_version, 1,
-                          None, slave_of_id=self.master.id)
-
 
 def trivial_key_function(id):
     return id * id