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876 lines
25 KiB
ReStructuredText
876 lines
25 KiB
ReStructuredText
==========================
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Introduction to librados
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==========================
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The :term:`Ceph Storage Cluster` provides the basic storage service that allows
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:term:`Ceph` to uniquely deliver **object, block, and file storage** in one
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unified system. However, you are not limited to using the RESTful, block, or
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POSIX interfaces. Based upon :abbr:`RADOS (Reliable Autonomic Distributed Object
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Store)`, the ``librados`` API enables you to create your own interface to the
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Ceph Storage Cluster.
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The ``librados`` API enables you to interact with the two types of daemons in
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the Ceph Storage Cluster:
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- The :term:`Ceph Monitor`, which maintains a master copy of the cluster map.
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- The :term:`Ceph OSD Daemon` (OSD), which stores data as objects on a storage node.
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.. ditaa::
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+---------------------------------+
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| Ceph Storage Cluster Protocol |
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| (librados) |
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+---------------------------------+
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+---------------+ +---------------+
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| OSDs | | Monitors |
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+---------------+ +---------------+
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This guide provides a high-level introduction to using ``librados``.
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Refer to :doc:`../../architecture` for additional details of the Ceph
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Storage Cluster. To use the API, you need a running Ceph Storage Cluster.
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See `Installation (Quick)`_ for details.
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Step 1: Getting librados
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========================
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Your client application must bind with ``librados`` to connect to the Ceph
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Storage Cluster. You must install ``librados`` and any required packages to
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write applications that use ``librados``. The ``librados`` API is written in
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C++, with additional bindings for C, Python and Java.
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Getting librados for C/C++
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--------------------------
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To install ``librados`` development support files for C/C++ on Debian/Ubuntu
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distributions, execute the following::
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sudo apt-get install librados-dev
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To install ``librados`` development support files for C/C++ on RHEL/CentOS
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distributions, execute the following::
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sudo yum install ceph-devel
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Once you install ``librados`` for developers, you can find the required
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headers for C/C++ under ``/usr/include/rados``. ::
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ls /usr/include/rados
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Getting librados for Python
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---------------------------
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The ``rados.py`` modules provides ``librados`` support to Python
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applications. The ``librados-dev`` package for Debian/Ubuntu
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and the ``ceph-devel`` package for RHEL/CentOS will install the
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``python-ceph`` package for you. You may install ``python-ceph``
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directly too.
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To install ``librados`` development support files for Python on Debian/Ubuntu
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distributions, execute the following::
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sudo apt-get install python-ceph
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To install ``librados`` development support files for C/C++ on RHEL/CentOS
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distributions, execute the following::
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sudo yum install python-ceph
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You can find the module under ``/usr/share/pyshared`` on Debian systems,
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or under ``/usr/lib/python*/site-packages`` on CentOS/RHEL systems.
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Getting librados for Java
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-------------------------
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To install ``librados`` for Java, you need to execute the following procedure:
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#. Install ``jna.jar``. For Debian/Ubuntu, execute::
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sudo apt-get install libjna-java
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For CentOS/RHEL, execute::
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sudo yum install jna
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The JAR files are located in ``/usr/share/java``.
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#. Clone the ``rados-java`` repository::
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git clone --recursive https://github.com/ceph/rados-java.git
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#. Build the ``rados-java`` repository::
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cd rados-java
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ant
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The JAR file is located under ``rados-java/target``.
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#. Copy the JAR for RADOS to a common location (e.g., ``/usr/share/java``) and
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ensure that it and the JNA JAR are in your JVM's classpath. For example::
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sudo cp target/rados-0.1.3.jar /usr/share/java/rados-0.1.3.jar
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sudo ln -s /usr/share/java/jna-3.2.7.jar /usr/lib/jvm/default-java/jre/lib/ext/jna-3.2.7.jar
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sudo ln -s /usr/share/java/rados-0.1.3.jar /usr/lib/jvm/default-java/jre/lib/ext/rados-0.1.3.jar
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To build the documentation, execute the following::
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ant docs
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Step 2: Configuring a Cluster Handle
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====================================
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A :term:`Ceph Client`, via ``librados``, interacts directly with OSDs to store
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and retrieve data. To interact with OSDs, the client app must invoke
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``librados`` and connect to a Ceph Monitor. Once connected, ``librados``
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retrieves the :term:`Cluster Map` from the Ceph Monitor. When the client app
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wants to read or write data, it creates an I/O context and binds to a
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:term:`pool`. The pool has an associated :term:`ruleset` that defines how it
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will place data in the storage cluster. Via the I/O context, the client
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provides the object name to ``librados``, which takes the object name
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and the cluster map (i.e., the topology of the cluster) and `computes`_ the
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placement group and `OSD`_ for locating the data. Then the client application
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can read or write data. The client app doesn't need to learn about the topology
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of the cluster directly.
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.. ditaa::
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+--------+ Retrieves +---------------+
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| Client |------------>| Cluster Map |
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+--------+ +---------------+
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|
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v Writes
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/-----\
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| obj |
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\-----/
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| To
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v
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+--------+ +---------------+
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| Pool |---------->| CRUSH Ruleset |
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+--------+ Selects +---------------+
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The Ceph Storage Cluster handle encapsulates the client configuration, including:
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- The `user ID`_ for ``rados_create()`` or user name for ``rados_create2()``
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(preferred).
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- The :term:`cephx` authentication key
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- The monitor ID and IP address
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- Logging levels
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- Debugging levels
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Thus, the first steps in using the cluster from your app are to 1) create
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a cluster handle that your app will use to connect to the storage cluster,
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and then 2) use that handle to connect. To connect to the cluster, the
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app must supply a monitor address, a username and an authentication key
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(cephx is enabled by default).
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.. tip:: Talking to different Ceph Storage Clusters – or to the same cluster
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with different users – requires different cluster handles.
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RADOS provides a number of ways for you to set the required values. For
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the monitor and encryption key settings, an easy way to handle them is to ensure
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that your Ceph configuration file contains a ``keyring`` path to a keyring file
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and at least one monitor address (e.g,. ``mon host``). For example::
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[global]
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mon host = 192.168.1.1
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keyring = /etc/ceph/ceph.client.admin.keyring
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Once you create the handle, you can read a Ceph configuration file to configure
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the handle. You can also pass arguments to your app and parse them with the
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function for parsing command line arguments (e.g., ``rados_conf_parse_argv()``),
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or parse Ceph environment variables (e.g., ``rados_conf_parse_env()``). Some
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wrappers may not implement convenience methods, so you may need to implement
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these capabilities. The following diagram provides a high-level flow for the
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initial connection.
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.. ditaa:: +---------+ +---------+
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| Client | | Monitor |
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+---------+ +---------+
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| |
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|-----+ create |
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| | cluster |
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|<----+ handle |
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| |
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|-----+ read |
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| | config |
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|<----+ file |
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| |
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| connect |
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|-------------->|
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| |
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|<--------------|
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| connected |
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| |
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Once connected, your app can invoke functions that affect the whole cluster
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with only the cluster handle. For example, once you have a cluster
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handle, you can:
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- Get cluster statistics
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- Use Pool Operation (exists, create, list, delete)
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- Get and set the configuration
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One of the powerful features of Ceph is the ability to bind to different pools.
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Each pool may have a different number of placement groups, object replicas and
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replication strategies. For example, a pool could be set up as a "hot" pool that
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uses SSDs for frequently used objects or a "cold" pool that uses erasure coding.
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The main difference in the various ``librados`` bindings is between C and
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the object-oriented bindings for C++, Java and Python. The object-oriented
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bindings use objects to represent cluster handles, IO Contexts, iterators,
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exceptions, etc.
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C Example
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---------
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For C, creating a simple cluster handle using the ``admin`` user, configuring
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it and connecting to the cluster might look something like this:
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.. code-block:: c
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#include <stdio.h>
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#include <string.h>
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#include <rados/librados.h>
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int main (int argc, char argv**)
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{
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/* Declare the cluster handle and required arguments. */
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rados_t cluster;
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char cluster_name[] = "ceph";
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char user_name[] = "client.admin";
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uint64_t flags;
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/* Initialize the cluster handle with the "ceph" cluster name and the "client.admin" user */
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int err;
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err = rados_create2(&cluster, cluster_name, user_name, flags);
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if (err < 0) {
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fprintf(stderr, "%s: Couldn't create the cluster handle! %s\n", argv[0], strerror(-err));
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exit(EXIT_FAILURE);
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} else {
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printf("\nCreated a cluster handle.\n");
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}
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/* Read a Ceph configuration file to configure the cluster handle. */
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err = rados_conf_read_file(cluster, "/etc/ceph/ceph.conf");
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if (err < 0) {
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fprintf(stderr, "%s: cannot read config file: %s\n", argv[0], strerror(-err));
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exit(EXIT_FAILURE);
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} else {
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printf("\nRead the config file.\n");
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}
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/* Read command line arguments */
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err = rados_conf_parse_argv(cluster, argc, argv);
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if (err < 0) {
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fprintf(stderr, "%s: cannot parse command line arguments: %s\n", argv[0], strerror(-err));
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exit(EXIT_FAILURE);
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} else {
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printf("\nRead the command line arguments.\n");
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}
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/* Connect to the cluster */
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err = rados_connect(cluster);
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if (err < 0) {
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fprintf(stderr, "%s: cannot connect to cluster: %s\n", argv[0], strerror(-err));
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exit(EXIT_FAILURE);
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} else {
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printf("\nConnected to the cluster.\n");
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}
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}
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Compile your client and link to ``librados`` using ``-lrados``. For example::
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gcc ceph-client.c -lrados -o ceph-client
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C++ Example
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-----------
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The Ceph project provides a C++ example in the ``ceph/examples/librados``
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directory. For C++, a simple cluster handle using the ``admin`` user requires
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you to initialize a ``librados::Rados`` cluster handle object:
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.. code-block:: c++
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#include <iostream>
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#include <string>
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#include <rados/librados.hpp>
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int main(int argc, const char **argv)
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{
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int ret = 0;
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/* Declare the cluster handle and required variables. */
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librados::Rados cluster;
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char cluster_name[] = "ceph";
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char user_name[] = "client.admin";
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uint64_t flags;
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/* Initialize the cluster handle with the "ceph" cluster name and "client.admin" user */
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{
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ret = cluster.init2(user_name, cluster_name, flags);
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if (ret < 0) {
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std::cerr << "Couldn't initialize the cluster handle! error " << ret << std::endl;
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ret = EXIT_FAILURE;
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return 1;
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} else {
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std::cout << "Created a cluster handle." << std::endl;
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}
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}
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/* Read a Ceph configuration file to configure the cluster handle. */
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{
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ret = cluster.conf_read_file("/etc/ceph/ceph.conf");
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if (ret < 0) {
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std::cerr << "Couldn't read the Ceph configuration file! error " << ret << std::endl;
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ret = EXIT_FAILURE;
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return 1;
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} else {
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std::cout << "Read the Ceph configuration file." << std::endl;
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}
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}
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/* Read command line arguments */
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{
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ret = cluster.conf_parse_argv(argc, argv);
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if (ret < 0) {
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std::cerr << "Couldn't parse command line options! error " << ret << std::endl;
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ret = EXIT_FAILURE;
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return 1;
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} else {
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std::cout << "Parsed command line options." << std::endl;
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}
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}
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/* Connect to the cluster */
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{
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ret = cluster.connect();
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if (ret < 0) {
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std::cerr << "Couldn't connect to cluster! error " << ret << std::endl;
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ret = EXIT_FAILURE;
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return 1;
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} else {
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std::cout << "Connected to the cluster." << std::endl;
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}
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}
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return 0;
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}
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Compile the source; then, link ``librados`` using ``-lrados``.
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For example::
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g++ -g -c ceph-client.cc -o ceph-client.o
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g++ -g ceph-client.o -lrados -o ceph-client
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Python Example
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--------------
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Python uses the ``admin`` id and the ``ceph`` cluster name by default, and
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will read the standard ``ceph.conf`` file if the conffile parameter is
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set to the empty string. The Python binding converts C++ errors
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into exceptions.
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.. code-block:: python
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import rados
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try:
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cluster = rados.Rados(conffile='')
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except TypeError as e:
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print 'Argument validation error: ', e
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raise e
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print "Created cluster handle."
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try:
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cluster.connect()
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except Exception as e:
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print "connection error: ", e
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raise e
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finally:
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print "Connected to the cluster."
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Execute the example to verify that it connects to your cluster. ::
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python ceph-client.py
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Java Example
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------------
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Java requires you to specify the user ID (``admin``) or user name
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(``client.admin``), and uses the ``ceph`` cluster name by default . The Java
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binding converts C++-based errors into exceptions.
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.. code-block:: java
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import com.ceph.rados.Rados;
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import com.ceph.rados.RadosException;
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import java.io.File;
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public class CephClient {
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public static void main (String args[]){
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try {
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cluster = rados.Rados(None, "client.admin", "ceph")
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print "Created cluster handle."
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File f = new File("/etc/ceph/ceph.conf");
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cluster.confReadFile(f);
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System.out.println("Read the configuration file.");
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cluster.connect();
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System.out.println("Connected to the cluster.");
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} catch (RadosException e) {
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System.out.println(e.getMessage() + ": " + e.getReturnValue());
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}
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}
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}
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Compile the source; then, run it. If you have copied the JAR to
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``/usr/share/java`` and sym linked from your ``ext`` directory, you won't need
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to specify the classpath. For example::
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javac CephClient.java
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java CephClient
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Step 3: Creating an I/O Context
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===============================
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Once your app has a cluster handle and a connection to a Ceph Storage Cluster,
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you may create an I/O Context and begin reading and writing data. An I/O Context
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binds the connection to a specific pool. The user must have appropriate
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`CAPS`_ permissions to access the specified pool. For example, a user with read
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access but not write access will only be able to read data. I/O Context
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functionality includes:
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- Write/read data and extended attributes
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- List and iterate over objects and extended attributes
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- Snapshot pools, list snapshots, etc.
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.. ditaa:: +---------+ +---------+ +---------+
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| Client | | Monitor | | OSD |
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+---------+ +---------+ +---------+
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| | |
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|-----+ create | |
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| | I/O | |
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|<----+ context | |
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| | |
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| write data | |
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|---------------+-------------->|
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| | |
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| write ack | |
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|<--------------+---------------|
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| | |
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| write xattr | |
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|---------------+-------------->|
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| | |
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| xattr ack | |
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|<--------------+---------------|
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| | |
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| read data | |
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|---------------+-------------->|
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| | |
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| read ack | |
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|<--------------+---------------|
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| | |
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| remove data | |
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|---------------+-------------->|
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| | |
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| remove ack | |
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|<--------------+---------------|
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RADOS enables you to interact both synchronously and asynchronously. Once your
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app has an I/O Context, read/write operations only require you to know the
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object/xattr name. The CRUSH algorithm encapsulated in ``librados`` uses the
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cluster map to identify the appropriate OSD. OSD daemons handle the replication,
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as described in `Smart Daemons Enable Hyperscale`_. The ``librados`` library also
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maps objects to placement groups, as described in `Calculating PG IDs`_.
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The following examples use the default ``data`` pool. However, you may also
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use the API to list pools, ensure they exist, or create and delete pools. For
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the write operations, the examples illustrate how to use synchronous mode. For
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the read operations, the examples illustrate how to use asynchronous mode.
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.. important:: Use caution when deleting pools with this API. If you delete
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a pool, the pool and ALL DATA in the pool will be lost.
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C Example
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---------
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.. code-block:: c
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#include <stdio.h>
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#include <string.h>
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#include <rados/librados.h>
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int main (int argc, const char argv**)
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{
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/*
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* Continued from previous C example, where cluster handle and
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* connection are established. First declare an I/O Context.
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*/
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rados_ioctx_t io;
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char *poolname = "data";
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err = rados_ioctx_create(cluster, poolname, &io);
|
||
if (err < 0) {
|
||
fprintf(stderr, "%s: cannot open rados pool %s: %s\n", argv[0], poolname, strerror(-err));
|
||
rados_shutdown(cluster);
|
||
exit(EXIT_FAILURE);
|
||
} else {
|
||
printf("\nCreated I/O context.\n");
|
||
}
|
||
|
||
/* Write data to the cluster synchronously. */
|
||
err = rados_write(io, "hw", "Hello World!", 12, 0);
|
||
if (err < 0) {
|
||
fprintf(stderr, "%s: Cannot write object \"hw\" to pool %s: %s\n", argv[0], poolname, strerror(-err));
|
||
rados_ioctx_destroy(io);
|
||
rados_shutdown(cluster);
|
||
exit(1);
|
||
} else {
|
||
printf("\nWrote \"Hello World\" to object \"hw\".\n");
|
||
}
|
||
|
||
char xattr[] = "en_US";
|
||
err = rados_setxattr(io, "hw", "lang", xattr, 5);
|
||
if (err < 0) {
|
||
fprintf(stderr, "%s: Cannot write xattr to pool %s: %s\n", argv[0], poolname, strerror(-err));
|
||
rados_ioctx_destroy(io);
|
||
rados_shutdown(cluster);
|
||
exit(1);
|
||
} else {
|
||
printf("\nWrote \"en_US\" to xattr \"lang\" for object \"hw\".\n");
|
||
}
|
||
|
||
/*
|
||
* Read data from the cluster asynchronously.
|
||
* First, set up asynchronous I/O completion.
|
||
*/
|
||
rados_completion_t comp;
|
||
err = rados_aio_create_completion(NULL, NULL, NULL, &comp);
|
||
if (err < 0) {
|
||
fprintf(stderr, "%s: Could not create aio completion: %s\n", argv[0], strerror(-err));
|
||
rados_ioctx_destroy(io);
|
||
rados_shutdown(cluster);
|
||
exit(1);
|
||
} else {
|
||
printf("\nCreated AIO completion.\n");
|
||
}
|
||
|
||
/* Next, read data using rados_aio_read. */
|
||
char read_res[100];
|
||
err = rados_aio_read(io, "hw", comp, read_res, 12, 0);
|
||
if (err < 0) {
|
||
fprintf(stderr, "%s: Cannot read object. %s %s\n", argv[0], poolname, strerror(-err));
|
||
rados_ioctx_destroy(io);
|
||
rados_shutdown(cluster);
|
||
exit(1);
|
||
} else {
|
||
printf("\nRead object \"hw\". The contents are:\n %s \n", read_res);
|
||
}
|
||
|
||
/* Wait for the operation to complete */
|
||
rados_wait_for_complete(comp);
|
||
|
||
/* Release the asynchronous I/O complete handle to avoid memory leaks. */
|
||
rados_aio_release(comp);
|
||
|
||
|
||
char xattr_res[100];
|
||
err = rados_getxattr(io, "hw", "lang", xattr_res, 5);
|
||
if (err < 0) {
|
||
fprintf(stderr, "%s: Cannot read xattr. %s %s\n", argv[0], poolname, strerror(-err));
|
||
rados_ioctx_destroy(io);
|
||
rados_shutdown(cluster);
|
||
exit(1);
|
||
} else {
|
||
printf("\nRead xattr \"lang\" for object \"hw\". The contents are:\n %s \n", xattr_res);
|
||
}
|
||
|
||
err = rados_rmxattr(io, "hw", "lang");
|
||
if (err < 0) {
|
||
fprintf(stderr, "%s: Cannot remove xattr. %s %s\n", argv[0], poolname, strerror(-err));
|
||
rados_ioctx_destroy(io);
|
||
rados_shutdown(cluster);
|
||
exit(1);
|
||
} else {
|
||
printf("\nRemoved xattr \"lang\" for object \"hw\".\n");
|
||
}
|
||
|
||
err = rados_remove(io, "hw");
|
||
if (err < 0) {
|
||
fprintf(stderr, "%s: Cannot remove object. %s %s\n", argv[0], poolname, strerror(-err));
|
||
rados_ioctx_destroy(io);
|
||
rados_shutdown(cluster);
|
||
exit(1);
|
||
} else {
|
||
printf("\nRemoved object \"hw\".\n");
|
||
}
|
||
|
||
}
|
||
|
||
|
||
|
||
C++ Example
|
||
-----------
|
||
|
||
|
||
.. code-block:: c++
|
||
|
||
#include <iostream>
|
||
#include <string>
|
||
#include <rados/librados.hpp>
|
||
|
||
int main(int argc, const char **argv)
|
||
{
|
||
|
||
/* Continued from previous C++ example, where cluster handle and
|
||
* connection are established. First declare an I/O Context.
|
||
*/
|
||
|
||
librados::IoCtx io_ctx;
|
||
const char *pool_name = "data";
|
||
|
||
{
|
||
ret = cluster.ioctx_create(pool_name, io_ctx);
|
||
if (ret < 0) {
|
||
std::cerr << "Couldn't set up ioctx! error " << ret << std::endl;
|
||
exit(EXIT_FAILURE);
|
||
} else {
|
||
std::cout << "Created an ioctx for the pool." << std::endl;
|
||
}
|
||
}
|
||
|
||
|
||
/* Write an object synchronously. */
|
||
{
|
||
librados::bufferlist bl;
|
||
bl.append("Hello World!");
|
||
ret = io_ctx.write("hw", bl);
|
||
if (ret < 0) {
|
||
std::cerr << "Couldn't write object! error " << ret << std::endl;
|
||
exit(EXIT_FAILURE);
|
||
} else {
|
||
std::cout << "Wrote new object 'hw' " << std::endl;
|
||
}
|
||
}
|
||
|
||
|
||
/*
|
||
* Add an xattr to the object.
|
||
*/
|
||
{
|
||
librados::bufferlist lang_bl;
|
||
lang_bl.append("en_US");
|
||
ret = io_ctx.setxattr("hw", "lang", lang_bl);
|
||
if (ret < 0) {
|
||
std::cerr << "failed to set xattr version entry! error "
|
||
<< ret << std::endl;
|
||
exit(EXIT_FAILURE);
|
||
} else {
|
||
std::cout << "Set the xattr 'lang' on our object!" << std::endl;
|
||
}
|
||
}
|
||
|
||
|
||
/*
|
||
* Read the object back asynchronously.
|
||
*/
|
||
{
|
||
librados::bufferlist read_buf;
|
||
int read_len = 4194304;
|
||
|
||
//Create I/O Completion.
|
||
librados::AioCompletion *read_completion = librados::Rados::aio_create_completion();
|
||
|
||
//Send read request.
|
||
ret = io_ctx.aio_read("hw", read_completion, &read_buf, read_len, 0);
|
||
if (ret < 0) {
|
||
std::cerr << "Couldn't start read object! error " << ret << std::endl;
|
||
exit(EXIT_FAILURE);
|
||
}
|
||
|
||
// Wait for the request to complete, and check that it succeeded.
|
||
read_completion->wait_for_complete();
|
||
ret = read_completion->get_return_value();
|
||
if (ret < 0) {
|
||
std::cerr << "Couldn't read object! error " << ret << std::endl;
|
||
exit(EXIT_FAILURE);
|
||
} else {
|
||
std::cout << "Read object hw asynchronously with contents.\n"
|
||
<< read_buf.c_str() << std::endl;
|
||
}
|
||
}
|
||
|
||
|
||
/*
|
||
* Read the xattr.
|
||
*/
|
||
{
|
||
librados::bufferlist lang_res;
|
||
ret = io_ctx.getxattr("hw", "lang", lang_res);
|
||
if (ret < 0) {
|
||
std::cerr << "failed to get xattr version entry! error "
|
||
<< ret << std::endl;
|
||
exit(EXIT_FAILURE);
|
||
} else {
|
||
std::cout << "Got the xattr 'lang' from object hw!"
|
||
<< lang_res.c_str() << std::endl;
|
||
}
|
||
}
|
||
|
||
|
||
/*
|
||
* Remove the xattr.
|
||
*/
|
||
{
|
||
ret = io_ctx.rmxattr("hw", "lang");
|
||
if (ret < 0) {
|
||
std::cerr << "Failed to remove xattr! error "
|
||
<< ret << std::endl;
|
||
exit(EXIT_FAILURE);
|
||
} else {
|
||
std::cout << "Removed the xattr 'lang' from our object!" << std::endl;
|
||
}
|
||
}
|
||
|
||
/*
|
||
* Remove the object.
|
||
*/
|
||
{
|
||
ret = io_ctx.remove("hw");
|
||
if (ret < 0) {
|
||
std::cerr << "Couldn't remove object! error " << ret << std::endl;
|
||
exit(EXIT_FAILURE);
|
||
} else {
|
||
std::cout << "Removed object 'hw'." << std::endl;
|
||
}
|
||
}
|
||
}
|
||
|
||
|
||
|
||
Python Example
|
||
--------------
|
||
|
||
.. code-block:: python
|
||
|
||
print "\n\nI/O Context and Object Operations"
|
||
print "================================="
|
||
|
||
print "\nCreating a context for the 'data' pool"
|
||
if not cluster.pool_exists('data'):
|
||
raise RuntimeError('No data pool exists')
|
||
ioctx = cluster.open_ioctx('data')
|
||
|
||
print "\nWriting object 'hw' with contents 'Hello World!' to pool 'data'."
|
||
ioctx.write("hw", "Hello World!")
|
||
print "Writing XATTR 'lang' with value 'en_US' to object 'hw'"
|
||
ioctx.set_xattr("hw", "lang", "en_US")
|
||
|
||
|
||
print "\nWriting object 'bm' with contents 'Bonjour tout le monde!' to pool 'data'."
|
||
ioctx.write("bm", "Bonjour tout le monde!")
|
||
print "Writing XATTR 'lang' with value 'fr_FR' to object 'bm'"
|
||
ioctx.set_xattr("bm", "lang", "fr_FR")
|
||
|
||
print "\nContents of object 'hw'\n------------------------"
|
||
print ioctx.read("hw")
|
||
|
||
print "\n\nGetting XATTR 'lang' from object 'hw'"
|
||
print ioctx.get_xattr("hw", "lang")
|
||
|
||
print "\nContents of object 'bm'\n------------------------"
|
||
print ioctx.read("bm")
|
||
|
||
print "Getting XATTR 'lang' from object 'bm'"
|
||
print ioctx.get_xattr("bm", "lang")
|
||
|
||
|
||
print "\nRemoving object 'hw'"
|
||
ioctx.remove_object("hw")
|
||
|
||
print "Removing object 'bm'"
|
||
ioctx.remove_object("bm")
|
||
|
||
|
||
|
||
Step 4: Closing Sessions
|
||
========================
|
||
|
||
Once your app finishes with the I/O Context and cluster handle, the app should
|
||
close the connection and shutdown the handle. For asynchronous I/O, the app
|
||
should also ensure that pending asynchronous operations have completed.
|
||
|
||
|
||
C Example
|
||
---------
|
||
|
||
.. code-block:: c
|
||
|
||
rados_ioctx_destroy(io);
|
||
rados_shutdown(cluster);
|
||
|
||
|
||
C++ Example
|
||
-----------
|
||
|
||
.. code-block:: c++
|
||
|
||
io_ctx.close();
|
||
cluster.shutdown();
|
||
|
||
|
||
Python Example
|
||
--------------
|
||
|
||
.. code-block:: python
|
||
|
||
print "\nClosing the connection."
|
||
ioctx.close()
|
||
|
||
print "Shutting down the handle."
|
||
cluster.shutdown()
|
||
|
||
|
||
|
||
|
||
|
||
.. _user ID: ../../operations/authentication#cephx-commandline-options
|
||
.. _CAPS: ../../operations/auth-intro#ceph-authorization-caps
|
||
.. _Installation (Quick): ../../../start
|
||
.. _Smart Daemons Enable Hyperscale: ../../../architecture#smart-daemons-enable-hyperscale
|
||
.. _Calculating PG IDs: ../../../architecture#calculating-pg-ids
|
||
.. _computes: ../../../architecture#calculating-pg-ids
|
||
.. _OSD: ../../../architecture#mapping-pgs-to-osds
|