X-Git-Url: https://gerrit.opnfv.org/gerrit/gitweb?a=blobdiff_plain;f=src%2Fceph%2Fdoc%2Frbd%2Fapi%2Flibrbdpy.rst;fp=src%2Fceph%2Fdoc%2Frbd%2Fapi%2Flibrbdpy.rst;h=fa903312557fea5bc2c0e93fca757fdcb16fa71e;hb=812ff6ca9fcd3e629e49d4328905f33eee8ca3f5;hp=0000000000000000000000000000000000000000;hpb=15280273faafb77777eab341909a3f495cf248d9;p=stor4nfv.git

diff --git a/src/ceph/doc/rbd/api/librbdpy.rst b/src/ceph/doc/rbd/api/librbdpy.rst
new file mode 100644
index 0000000..fa90331
--- /dev/null
+++ b/src/ceph/doc/rbd/api/librbdpy.rst
@@ -0,0 +1,82 @@
+================
+ 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**3  # 4 GiB
+    rbd_inst.create(ioctx, 'myimage', size)
+
+To perform I/O on the image, you instantiate an :class:rbd.Image object::
+
+    image = rbd.Image(ioctx, '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 will 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**3  # 4 GiB
+            rbd_inst.create(ioctx, 'myimage', size)
+            image = rbd.Image(ioctx, '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**3  # 4 GiB
+            rbd_inst.create(ioctx, 'myimage', size)
+            with rbd.Image(ioctx, 'myimage') as image:
+                data = 'foo' * 200
+                image.write(data, 0)
+
+API Reference
+=============
+
+.. automodule:: rbd
+    :members: RBD, Image, SnapIterator