doc: add documentation for librbd python bindings

Signed-off-by: Josh Durgin <josh.durgin@dreamhost.com>

3 files changed, 83 insertions, 1 deletions

diff --git a/admin/build-doc b/admin/build-doc
index 622d7c84031..2b3beedc074 100755
--- a/admin/build-doc
+++ b/admin/build-doc
@@ -36,5 +36,5 @@ cd ..
 install -d -m0755 \
     output/html \
     output/man
-./virtualenv/bin/sphinx-build -a -b dirhtml -d doctrees ../doc output/html
+PYTHONPATH=`pwd`/../src/pybind ./virtualenv/bin/sphinx-build -a -b dirhtml -d doctrees ../doc output/html
 ./virtualenv/bin/sphinx-build -a -b man -d doctrees ../doc output/man
diff --git a/doc/api/librbdpy.rst b/doc/api/librbdpy.rst
new file mode 100644
index 00000000000..6298a6e41e1
--- /dev/null
+++ b/doc/api/librbdpy.rst
@@ -0,0 +1,81 @@
+================
+ Librbd (Python)
+================
+
+.. highlight:: python
+
+The `rbd` python module provides file-like access to RBD images.
+
+
+Example: Creating and writing to an image
+=========================================
+
+To use `rbd`, you must first connect to RADOS and open an IO
+context::
+
+    cluster = rados.Rados(conffile='my_ceph.conf')
+    cluster.connect()
+    ioctx = cluster.open_ioctx('mypool')
+
+Then you instantiate an :class:rbd.RBD object, which you use to create the
+image::
+
+    rbd_inst = rbd.RBD()
+    size = 4 * 1024 * 1024  # 4 GiB
+    rbd_inst.create('myimage', 4)
+
+To perform I/O on the image, you instantiate an :class:rbd.Image object::
+
+    image = rbd.Image('myimage')
+    data = 'foo' * 200
+    image.write(data, 0)
+
+This writes 'foo' to the first 600 bytes of the image. Note that data
+cannot be :type:unicode - `Librbd` does not know how to deal with
+characters wider than a :c:type:char.
+
+In the end, you'll want to close the image, the IO context and the connection to RADOS::
+
+    image.close()
+    ioctx.close()
+    cluster.shutdown()
+
+To be safe, each of these calls would need to be in a separate :finally
+block::
+
+    cluster = rados.Rados(conffile='my_ceph_conf')
+    try:
+        ioctx = cluster.open_ioctx('my_pool')
+        try:
+            rbd_inst = rbd.RBD()
+            size = 4 * 1024 * 1024  # 4 GiB
+            rbd_inst.create('myimage', 4)
+            image = rbd.Image('myimage')
+            try:
+                data = 'foo' * 200
+                image.write(data, 0)
+            finally:
+                image.close()
+        finally:
+            ioctx.close()
+    finally:
+        cluster.shutdown()
+
+This can be cumbersome, so the :class:Rados, :class:Ioctx, and :class:Image
+classes can be used as context managers that close/shutdown automatically (see
+:pep:`343`). Using them as context managers, the above example becomes::
+
+    with rados.Rados(conffile='my_ceph.conf') as cluster:
+        with cluster.open_ioctx('mypool') as ioctx:
+            rbd_inst = rbd.RBD()
+            size = 4 * 1024 * 1024  # 4 GiB
+            rbd_inst.create('myimage', 4)
+            with rbd.Image('myimage') is image:
+                data = 'foo' * 200
+                image.write(data, 0)
+
+API Reference
+=============
+
+.. automodule:: rbd
+    :members: RBD, Image, SnapIterator
diff --git a/doc/conf.py b/doc/conf.py
index afac33f816a..4dab00c1604 100644
--- a/doc/conf.py
+++ b/doc/conf.py
@@ -22,6 +22,7 @@ html_sidebars = {
 # ugly kludge until breathe is distutils-friendly
 import sys; sys.path.append('../build-doc/breathe')
 extensions = [
+    'sphinx.ext.autodoc',
     'sphinx.ext.graphviz',
     'sphinx.ext.todo',
     'breathe',