Using OpenStack Object Store

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Using OpenStack Object Store

Before working with the Object Store service, you’ll need to create a connection to your OpenStack cloud by following the Connect user guide. This will provide you with the conn variable used in the examples below.

The primary resources of the Object Store service are containers and objects.

Working with Containers

Listing Containers

To list existing containers, use the containers() method.

>>> for cont in conn.object_store.containers():
...     print cont
...
openstack.object_store.v1.container.Container: {u'count': 5,
u'bytes': 500, u'name': u'my container'}
openstack.object_store.v1.container.Container: {u'count': 0,
u'bytes': 0, u'name': u'empty container'}
openstack.object_store.v1.container.Container: {u'count': 100,
u'bytes': 1000000, u'name': u'another container'}

The containers method returns a generator which yields Container objects. It handles pagination for you, which can be adjusted via the limit argument. By default, the containers method will yield as many containers as the service will return, and it will continue requesting until it receives no more.

>>> for cont in conn.object_store.containers(limit=500):
...     print(cont)
...
<500 Containers>
... another request transparently made to the Object Store service
<500 more Containers>
...

Creating Containers

To create a container, use the create_container() method.

>>> cont = conn.object_store.create_container(name="new container")
>>> cont
openstack.object_store.v1.container.Container: {'name': u'new container'}

Working with Container Metadata

To get the metadata for a container, use the get_container_metadata() method. This method either takes the name of a container, or a Container object, and it returns a Container object with all of its metadata attributes set.

>>> cont = conn.object_store.get_container_metadata("new container")
openstack.object_store.v1.container.Container: {'content-length': '0',
'x-container-object-count': '0', 'name': u'new container',
'accept-ranges': 'bytes',
'x-trans-id': 'tx22c5de63466e4c05bb104-0054740c39',
'date': 'Tue, 25 Nov 2014 04:57:29 GMT',
'x-timestamp': '1416889793.23520', 'x-container-read': '.r:mysite.com',
'x-container-bytes-used': '0', 'content-type': 'text/plain; charset=utf-8'}

To set the metadata for a container, use the set_container_metadata() method. This method takes a Container object. For example, to grant another user write access to this container, you can set the write_ACL on a resource and pass it to set_container_metadata.

>>> cont.write_ACL = "big_project:another_user"
>>> conn.object_store.set_container_metadata(cont)
openstack.object_store.v1.container.Container: {'content-length': '0',
'x-container-object-count': '0',
'name': u'my new container', 'accept-ranges': 'bytes',
'x-trans-id': 'txc3ee751f971d41de9e9f4-0054740ec1',
'date': 'Tue, 25 Nov 2014 05:08:17 GMT',
'x-timestamp': '1416889793.23520', 'x-container-read': '.r:mysite.com',
'x-container-bytes-used': '0', 'content-type': 'text/plain; charset=utf-8',
'x-container-write': 'big_project:another_user'}

Working with Objects

Objects are held in containers. From an API standpoint, you work with them using similarly named methods, typically with an additional argument to specify their container.

Listing Objects

To list the objects that exist in a container, use the objects() method.

If you have a Container object, you can pass it to objects.

>>> print cont.name
pictures
>>> for obj in conn.object_store.objects(cont):
...     print obj
...
openstack.object_store.v1.container.Object:
{u'hash': u'0522d4ccdf9956badcb15c4087a0c4cb',
u'name': u'pictures/selfie.jpg', u'bytes': 15744,
'last-modified': u'2014-10-31T06:33:36.618640',
u'last_modified': u'2014-10-31T06:33:36.618640',
u'content_type': u'image/jpeg', 'container': u'pictures',
'content-type': u'image/jpeg'}
...

Similar to the containers() method, objects returns a generator which yields Object objects stored in the container. It also handles pagination for you, which you can adjust with the limit parameter, otherwise making each request for the maximum that your Object Store will return.

If you have the name of a container instead of an object, you can also pass that to the objects method.

>>> for obj in conn.object_store.objects("pictures".decode("utf8"),
                                         limit=100):
...     print obj
...
<100 Objects>
... another request transparently made to the Object Store service
<100 more Objects>

Getting Object Data

Once you have an Object, you get the data stored inside of it with the get_object_data() method.

>>> print ob.name
message.txt
>>> data = conn.object_store.get_object_data(ob)
>>> print data
Hello, world!

Additionally, if you want to save the object to disk, the download_object() convenience method takes an Object and a path to write the contents to.

>>> conn.object_store.download_object(ob, "the_message.txt")

Uploading Objects

Once you have data you’d like to store in the Object Store service, you use the upload_object() method. This method takes the data to be stored, along with at least an object name and the container it is to be stored in.

>>> hello = conn.object_store.upload_object(container="messages",
                                            name="helloworld.txt",
                                            data="Hello, world!")
>>> print hello
openstack.object_store.v1.container.Object: {'content-length': '0',
'container': u'messages', 'name': u'helloworld.txt',
'last-modified': 'Tue, 25 Nov 2014 17:39:29 GMT',
'etag': '5eb63bbbe01eeed093cb22bb8f5acdc3',
'x-trans-id': 'tx3035d41b03334aeaaf3dd-005474bed0',
'date': 'Tue, 25 Nov 2014 17:39:28 GMT',
'content-type': 'text/html; charset=UTF-8'}

Working with Object Metadata

Working with metadata on objects is identical to how it’s done with containers. You use the get_object_metadata() and set_object_metadata() methods.

The metadata attributes to be set can be found on the Object object.

>>> secret.delete_after = 300
>>> secret = conn.object_store.set_object_metadata(secret)

We set the delete_after value to 500 seconds, causing the object to be deleted in 300 seconds, or five minutes. That attribute corresponds to the X-Delete-After header value, which you can see is returned when we retreive the updated metadata.

>>> conn.object_store.get_object_metadata(ob)
openstack.object_store.v1.container.Object: {'content-length': '11',
'container': u'Secret Container',
'name': u'selfdestruct.txt', 'x-delete-after': 300,
'accept-ranges': 'bytes', 'last-modified': 'Tue, 25 Nov 2014 17:50:45 GMT',
'etag': '5eb63bbbe01eeed093cb22bb8f5acdc3',
'x-timestamp': '1416937844.36805',
'x-trans-id': 'tx5c3fd94adf7c4e1b8f334-005474c17b',
'date': 'Tue, 25 Nov 2014 17:50:51 GMT', 'content-type': 'text/plain'}
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