Add specs to resize a load balancer

This specification explains how the resizing mechanism can be implemented.

Change-Id: I9c3499b703bf0beab305cc071c74ae3acbcc4c24

doc/source/contributor/index.rst

@@ -98,6 +98,15 @@ Version 14.0 (caracal)
 
    specs/version14.0/*
 
+Version 15.0 (Dalmatian)
+````````````````````````
+
+.. toctree::
+   :glob:
+   :maxdepth: 1
+
+   specs/version15.0/*
+
 .. only:: latex
 
    Module Reference

specs/version15.0/resize.rst

@@ -0,0 +1,149 @@
+======================
+Load balancer resizing
+======================
+Link to blueprint: https://blueprints.launchpad.net/octavia/+spec/octavia-resize-loadbalancer
+
+This spec's goal is to describe the functionality of resizing of load
+balancers. The main aim of this new feature is to enable you to change the
+flavor directly from the API.
+
+Problem description
+===================
+Today's users can't easily change the flavor. They have to recreate their load
+balancer with the new flavor and migrate their configurations such as
+l7 rules, listeners, etc.
+This can be very tedious for a user who wants to quickly resize his load
+balancer. It can be especially complicated to script.
+
+Proposed change
+===============
+The proposed change would be to add an endpoint to allow load balancer
+resizing. It would also be easy to cancel a resize in progress and return
+to the previous flavor.
+
+To achieve this, the endpoint will launch a workflow to initiate a failover
+with the new flavor ID. This will involve patching the `get_failover_LB_flow`
+to add the `flavorId` parameter. At the end of the workflow the `flavor_id`
+will be updated in the `loadbalancer` table.
+
+A check will be added before the start of the failover to prevent migration
+to a flavor profile topology different from the original one. A user cannot
+migrate from a flavorprofile standalone to active/passive.
+
+If a problem occurs during resizing, the load balancer status will be set
+to ERROR. The flavor will remain the same in database, allowing the user
+to perform a failover or retry the same call.
+
+Alternatives
+------------
+ * Rebuild the vm of the loadbalancer with the new flavor compute.
+ * Use the "backup" and "restore".
+
+
+Data model impact
+-----------------
+None
+
+
+REST API impact
+---------------
+Add one endpoint in `/v2.0/lbaas/loadbalancers`.
+
+To run this endpoint, the user must have the role `load-balancer:write"`.
+
+Start a resize of a load balancer::
+
+    PUT /v2.0/lbaas/loadbalancers/{loadbalancer_id}/resize
+
+    {
+        "new_flavor_id": "6d425a5e-429f-4848-b240-ab31c6d211e4"
+    }
+
+.. list-table:: Response code
+    :widths: 15 50
+    :header-rows: 1
+
+    * - Code
+      - Description
+    * - 202 Accepted
+      - Resize starting
+    * - 400 Bad request
+      - Resize object is invalid
+    * - 401 Unauthorized
+      - X-Auth-Token is invalid
+    * - 403 Forbidden
+      - X-Auth-Token is valid, but the associated project does not have
+        the appropriate role/scope
+    * - 404 Not Found
+      - Load balancer not found
+
+Security impact
+---------------
+None
+
+Notifications impact
+--------------------
+Add a notification to announce a loadbalancer resize.
+
+Other end user impact
+---------------------
+Add one command to launch resize in CLI client.
+
+Start a resize: openstack loadbalancer resize \
+                --flavor <flavor-id|flavor-name> \
+                <lb-id|lb-name>
+
+Add functions to resize in the `openstacksdk`.
+
+Performance Impact
+------------------
+None
+
+
+Other deployer impact
+---------------------
+None
+
+
+Developer impact
+----------------
+None
+
+
+Implementation
+==============
+
+Assignee(s)
+-----------
+TBD
+
+Work Items
+----------
+ - Create endpoints
+ - Patch the `get_failover_LB_flow` to add `flavorId` parameter.
+ - Add unit tests
+ - Add API functional tests
+ - Add tempest tests
+ - Update Octavia CLI and OpenstackSDK
+ - Write Documentation
+
+Dependencies
+============
+None
+
+Testing
+=======
+Tempest tests should be added for testing this new feature:
+ - Create a loadbalancer
+ - Try to resize
+
+Documentation Impact
+====================
+ - A user guide to explain how that works.
+ - Add a note on the fact that some flavor changes can cause data plane
+   downtime. Similarly, going from a newer image tag to an older one may
+   cause failures or features to be disabled.
+
+References
+==========
+None