From b1b58239dbe4dc05852a35528d87a2257ceaaf7a Mon Sep 17 00:00:00 2001
From: Zhenguo Niu <Niu.ZGlinux@gmail.com>
Date: Tue, 6 Jun 2017 17:34:43 +0800
Subject: [PATCH] [DOC] Add states and transitons diagram

Change-Id: Ifcc942612dd2371d9af1ec5174f61c2aeec4a008
---
 doc/source/conf.py    |  1 +
 doc/source/index.rst  |  8 ++++++-
 doc/source/states.rst | 52 +++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 60 insertions(+), 1 deletion(-)
 create mode 100644 doc/source/states.rst

diff --git a/doc/source/conf.py b/doc/source/conf.py
index 7bf9cb3d..82be7947 100755
--- a/doc/source/conf.py
+++ b/doc/source/conf.py
@@ -24,6 +24,7 @@ extensions = [
     'openstackdocstheme',
     'oslo_config.sphinxconfiggen',
     'oslo_policy.sphinxpolicygen',
+    'sphinx.ext.graphviz',
 ]
 
 # openstackdocstheme options
diff --git a/doc/source/index.rst b/doc/source/index.rst
index e2d317d3..5fd2de70 100644
--- a/doc/source/index.rst
+++ b/doc/source/index.rst
@@ -53,6 +53,13 @@ project.
   Developer Contribution Guide <dev/code-contribution-guide>
   Setting Up Your Development Environment <dev/dev-quickstart>
 
+The following pages describe the architecture of the service.
+
+.. toctree::
+  :maxdepth: 1
+
+  States and Transitions <states>
+
 Advanced testing and guides
 ---------------------------
 
@@ -61,7 +68,6 @@ Advanced testing and guides
 
     dev/gmr
 
-
 Administrator's Guide
 =====================
 
diff --git a/doc/source/states.rst b/doc/source/states.rst
new file mode 100644
index 00000000..46882714
--- /dev/null
+++ b/doc/source/states.rst
@@ -0,0 +1,52 @@
+States and Transitions
+======================
+
+The following diagram shows the states that a server goes through
+during the lifetime.
+
+Allowed State Transitions
+--------------------------
+
+.. graphviz::
+
+  digraph states {
+    graph [pad=".35", ranksep="0.65", nodesep="0.55", concentrate=true];
+    node [fontsize=10 fontname="Monospace"];
+    edge [arrowhead="normal", arrowsize="0.8"];
+    label="All states are allowed to transition to DELETING, MAINTENANCE and ERROR.";
+    forcelabels=true;
+    labelloc=bottom;
+    labeljust=left;
+
+    /* states */
+    building [label="BUILDING"]
+    active [label="ACTIVE"]
+    stopped [label="STOPPED"]
+    powering_on [label="POWERING_ON"]
+    powering_off [label="POWERING_OFF"]
+    soft_powering_off [label="SOFT_POWERING_OFF"]
+    rebooting [label="REBOOTING"]
+    soft_rebooting [label="SOFT_REBOOTING"]
+    rebuilding [label="REBUILDING"]
+    deleting [label="DELETING", color="red"]
+    error [label="ERROR", color="red"]
+    maintenance [label="MAINTENANCE", color="red"]
+
+    /* transitions [action] */
+    active -> rebuilding
+    active -> powering_off
+    active -> soft_powering_off
+    active -> rebooting
+    active -> soft_rebooting
+
+    stopped -> powering_on
+    stopped -> rebuilding
+
+    building -> active
+    rebuilding -> active
+    powering_on -> active
+    powering_off -> stopped
+    soft_powering_off -> stopped
+    rebooting -> active
+    soft_rebooting -> active
+  }