doc: use plantweb as fallback of sphinx-ditaa

RTD does not support installing system packages, the only ways to install
dependencies are setuptools and pip. while ditaa is a tool written in
Java. so we need to find a native python tool allowing us to render ditaa
images. plantweb is able to the web service for rendering the ditaa
diagram. so let's use it as a fallback if "ditaa" is not around.

also start a new line after the directive, otherwise planweb server will
return 500 at seeing the diagram.

Signed-off-by: Kefu Chai <kchai@redhat.com>

8 files changed, 32 insertions, 20 deletions

diff --git a/doc/rados/api/librados-intro.rst b/doc/rados/api/librados-intro.rst
index c63a255897c..7179438a84d 100644
--- a/doc/rados/api/librados-intro.rst
+++ b/doc/rados/api/librados-intro.rst
@@ -15,7 +15,7 @@ the Ceph Storage Cluster:
 - The :term:`Ceph Monitor`, which maintains a master copy of the cluster map. 
 - The :term:`Ceph OSD Daemon` (OSD), which stores data as objects on a storage node.
 
-.. ditaa::  
+.. ditaa::
             +---------------------------------+
             |  Ceph Storage Cluster Protocol  |
             |           (librados)            |
@@ -165,7 +165,7 @@ placement group and `OSD`_  for locating the data. Then the client application
 can read or write data. The client app doesn't need to learn about the topology
 of the cluster directly.
 
-.. ditaa:: 
+.. ditaa::
             +--------+  Retrieves  +---------------+
             | Client |------------>|  Cluster Map  |
             +--------+             +---------------+
@@ -217,7 +217,8 @@ these capabilities. The following diagram provides a high-level flow for the
 initial connection.
 
 
-.. ditaa:: +---------+     +---------+
+.. ditaa::
+           +---------+     +---------+
            | Client  |     | Monitor |
            +---------+     +---------+
                 |               |
@@ -521,7 +522,8 @@ functionality includes:
 - Snapshot pools, list snapshots, etc.
 
 
-.. ditaa:: +---------+     +---------+     +---------+
+.. ditaa::
+           +---------+     +---------+     +---------+
            | Client  |     | Monitor |     |   OSD   |
            +---------+     +---------+     +---------+
                 |               |               |
diff --git a/doc/rados/configuration/mon-config-ref.rst b/doc/rados/configuration/mon-config-ref.rst
index dbfc20b9084..e93cd28b7d7 100644
--- a/doc/rados/configuration/mon-config-ref.rst
+++ b/doc/rados/configuration/mon-config-ref.rst
@@ -34,8 +34,7 @@ Monitors can query the most recent version of the cluster map during sync
 operations. Ceph Monitors leverage the key/value store's snapshots and iterators
 (using leveldb) to perform store-wide synchronization.
 
-.. ditaa:: 
-
+.. ditaa::
  /-------------\               /-------------\
  |   Monitor   | Write Changes |    Paxos    |
  |   cCCC      +-------------->+   cCCC      |
@@ -505,7 +504,6 @@ Ceph Clients to read and write data. So the Ceph Storage Cluster's operating
 capacity is 95TB, not 99TB.
 
 .. ditaa::
-
  +--------+  +--------+  +--------+  +--------+  +--------+  +--------+
  | Rack 1 |  | Rack 2 |  | Rack 3 |  | Rack 4 |  | Rack 5 |  | Rack 6 |
  | cCCC   |  | cF00   |  | cCCC   |  | cCCC   |  | cCCC   |  | cCCC   |
@@ -636,7 +634,8 @@ fallen behind the other monitors. The requester asks the leader to synchronize,
 and the leader tells the requester to synchronize with a provider.
 
 
-.. ditaa:: +-----------+          +---------+          +----------+
+.. ditaa::
+           +-----------+          +---------+          +----------+
            | Requester |          | Leader  |          | Provider |
            +-----------+          +---------+          +----------+
                   |                    |                     |
diff --git a/doc/rados/configuration/mon-osd-interaction.rst b/doc/rados/configuration/mon-osd-interaction.rst
index a7324ebb0e5..6ef66265553 100644
--- a/doc/rados/configuration/mon-osd-interaction.rst
+++ b/doc/rados/configuration/mon-osd-interaction.rst
@@ -34,7 +34,8 @@ and ``[osd]`` or ``[global]`` section of your Ceph configuration file,
 or by setting the value at runtime.
 
 
-.. ditaa:: +---------+          +---------+
+.. ditaa::
+           +---------+          +---------+
            |  OSD 1  |          |  OSD 2  |
            +---------+          +---------+
                 |                    |
@@ -89,7 +90,9 @@ and ``mon osd reporter subtree level`` settings  under the ``[mon]`` section of
 your Ceph configuration file, or by setting the value at runtime.
 
 
-.. ditaa:: +---------+     +---------+      +---------+
+.. ditaa::
+
+           +---------+     +---------+      +---------+
            |  OSD 1  |     |  OSD 2  |      | Monitor |
            +---------+     +---------+      +---------+
                 |               |                |
@@ -118,7 +121,9 @@ Ceph Monitor heartbeat interval by adding an ``osd mon heartbeat interval``
 setting under the ``[osd]`` section of your Ceph configuration file, or by
 setting the value at runtime.
 
-.. ditaa:: +---------+     +---------+     +-------+     +---------+
+.. ditaa::
+
+           +---------+     +---------+     +-------+     +---------+
            |  OSD 1  |     |  OSD 2  |     | OSD 3 |     | Monitor |
            +---------+     +---------+     +-------+     +---------+
                 |               |              |              |
@@ -161,7 +166,9 @@ interval max`` setting under the ``[osd]`` section of your Ceph configuration
 file, or by setting the value at runtime.
 
 
-.. ditaa:: +---------+          +---------+
+.. ditaa::
+
+           +---------+          +---------+
            |  OSD 1  |          | Monitor |
            +---------+          +---------+
                 |                    |
diff --git a/doc/rados/configuration/network-config-ref.rst b/doc/rados/configuration/network-config-ref.rst
index 41da0a17528..bd49a87b310 100644
--- a/doc/rados/configuration/network-config-ref.rst
+++ b/doc/rados/configuration/network-config-ref.rst
@@ -112,7 +112,7 @@ Each Ceph OSD Daemon on a Ceph Node may use up to four ports:
 #. One for sending data to other OSDs.
 #. Two for heartbeating on each interface.
 
-.. ditaa:: 
+.. ditaa::
               /---------------\
               |      OSD      |
               |           +---+----------------+-----------+
diff --git a/doc/rados/operations/cache-tiering.rst b/doc/rados/operations/cache-tiering.rst
index c825c22c303..237b6e3c9f3 100644
--- a/doc/rados/operations/cache-tiering.rst
+++ b/doc/rados/operations/cache-tiering.rst
@@ -13,7 +13,7 @@ tier. So the cache tier and the backing storage tier are completely transparent
 to Ceph clients.
 
 
-.. ditaa:: 
+.. ditaa::
            +-------------+
            | Ceph Client |
            +------+------+
diff --git a/doc/rados/operations/monitoring-osd-pg.rst b/doc/rados/operations/monitoring-osd-pg.rst
index 630d268b458..08b70dd4d51 100644
--- a/doc/rados/operations/monitoring-osd-pg.rst
+++ b/doc/rados/operations/monitoring-osd-pg.rst
@@ -33,7 +33,9 @@ not assign placement groups to the OSD. If an OSD is ``down``, it should also be
 .. note:: If an OSD is ``down`` and ``in``, there is a problem and the cluster 
    will not be in a healthy state.
 
-.. ditaa:: +----------------+        +----------------+
+.. ditaa::
+
+           +----------------+        +----------------+
            |                |        |                |
            |   OSD #n In    |        |   OSD #n Up    |
            |                |        |                |
@@ -158,7 +160,9 @@ OSDs to establish agreement on the current state of the placement group
 (assuming a pool with 3 replicas of the PG).
 
 
-.. ditaa:: +---------+     +---------+     +-------+
+.. ditaa::
+
+           +---------+     +---------+     +-------+
            |  OSD 1  |     |  OSD 2  |     | OSD 3 |
            +---------+     +---------+     +-------+
                 |               |              |
@@ -265,8 +269,8 @@ group's Acting Set will peer. Once peering is complete, the placement group
 status should be ``active+clean``, which means a Ceph client can begin writing
 to the placement group.
 
-.. ditaa:: 
-         
+.. ditaa::
+
        /-----------\       /-----------\       /-----------\
        | Creating  |------>|  Peering  |------>|  Active   |
        \-----------/       \-----------/       \-----------/
diff --git a/doc/rados/operations/placement-groups.rst b/doc/rados/operations/placement-groups.rst
index dbeb2fe30c7..f7f2d110a8e 100644
--- a/doc/rados/operations/placement-groups.rst
+++ b/doc/rados/operations/placement-groups.rst
@@ -244,7 +244,6 @@ OSDs. For instance, in a replicated pool of size two, each placement
 group will store objects on two OSDs, as shown below.
 
 .. ditaa::
-
    +-----------------------+      +-----------------------+
    |  Placement Group #1   |      |  Placement Group #2   |
    |                       |      |                       |
diff --git a/doc/rados/operations/user-management.rst b/doc/rados/operations/user-management.rst
index 4d961d4be04..7b7713a83bd 100644
--- a/doc/rados/operations/user-management.rst
+++ b/doc/rados/operations/user-management.rst
@@ -9,7 +9,8 @@ authorization with the :term:`Ceph Storage Cluster`. Users are either
 individuals or system actors such as applications, which use Ceph clients to
 interact with the Ceph Storage Cluster daemons.
 
-.. ditaa::  +-----+
+.. ditaa::
+            +-----+
             | {o} |
             |     |
             +--+--+       /---------\               /---------\