Adds automatic ERD generation for the Octavia DB

This patch adds automatic Entity Relationship Diagraming (ERD) for
the Octavia database schema. The ERD will be available as part of the
Octavia developer reference documentation.

Story: 1558379
Task: 5271

Change-Id: I282b4128fcc72babd1a128d95ec0b3342802c2d4

.gitignore

@@ -8,6 +8,7 @@ covhtml/
 dist/
 doc/build
 doc/source/configuration/_static/octavia.policy.yaml.sample
+doc/source/contributor/devref/erd.svg
 doc/source/contributor/devref/flow_diagrams/
 doc/source/contributor/modules
 .idea/*

doc/source/conf.py

@@ -14,12 +14,27 @@
 import sys
 import subprocess
 import os
+
+from pydotplus import graphviz
+import sadisplay
+
+import octavia.db.models as models
 from tools import create_flow_docs
 
 # Generate our flow diagrams
 create_flow_docs.generate(
     'tools/flow-list.txt', 'doc/source/contributor/devref/flow_diagrams')
 
+# Generate entity relationship diagram
+desc = sadisplay.describe(
+    [getattr(models, attr) for attr in dir(models)],
+    show_methods=True,
+    show_properties=True,
+    show_indexes=True,
+)
+graph = graphviz.graph_from_dot_data(sadisplay.dot(desc).encode('utf-8'))
+graph.write('contributor/devref/erd.svg', format='svg')
+
 # If extensions (or modules to document with autodoc) are in another directory,
 # add these directories to sys.path here. If the directory is relative to the
 # documentation root, use os.path.abspath to make it absolute, like shown here.

doc/source/contributor/devref/erd.rst

@@ -0,0 +1,17 @@
+
+===================================
+Octavia Entity Relationship Diagram
+===================================
+
+Below is the current Octavia database data model.
+
+* Solid stars are primary key columns.
+* Hollow stars are foreign key columns.
+* Items labeled as "PROPERTY" are data model relationships and are not
+  present in the database.
+
+Click to enlarge the diagram.
+
+.. image:: erd.svg
+    :width: 660px
+    :target: ../../_images/erd.svg

test-requirements.txt

@@ -27,6 +27,7 @@ docutils>=0.11 # OSI-Approved Open Source, Public Domain
 sphinx>=1.6.2 # BSD
 graphviz!=0.5.0,>=0.4 # MIT License
 openstackdocstheme>=1.17.0 # Apache-2.0
+sadisplay>=0.4.8 # BSD
 
 # This needs to be installed after above modules
 pydotplus>=2.0.2 # MIT License