258 lines
12 KiB
XML
258 lines
12 KiB
XML
<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE section [
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<!-- Some useful entities borrowed from HTML -->
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<!ENTITY nbsp " ">
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<!-- Useful for describing APIs -->
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<!ENTITY PUT '<command xmlns="http://docbook.org/ns/docbook">PUT</command>'>
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<!ENTITY GET '<command xmlns="http://docbook.org/ns/docbook">GET</command>'>
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<!ENTITY POST '<command xmlns="http://docbook.org/ns/docbook">POST</command>'>
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]>
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<section xmlns="http://docbook.org/ns/docbook"
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xmlns:xi="http://www.w3.org/2001/XInclude"
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xmlns:xlink="http://www.w3.org/1999/xlink" version="5.0"
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xml:id="object_storage_api_overview">
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<title>Object Storage API overview</title>
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<para>OpenStack Object Storage is an object-based storage system
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that stores content and metadata as objects. You create,
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modify, and get objects and metadata by using the Object
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Storage API, which is implemented as a set of Representational
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State Transfer (REST) web services.</para>
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<para>For an introduction to OpenStack Object Storage, see <link
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xlink:href="http://docs.openstack.org/admin-guide-cloud/content/ch_admin-openstack-object-storage.html"
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>Object Storage</link> in the <citetitle>OpenStack Cloud
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Administrator Guide</citetitle>.</para>
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<para>You use the HTTPS (SSL) protocol to interact with Object
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Storage, and you use standard HTTP calls to perform API
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operations. You can also use language-specific APIs, which use
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the RESTful API, that make it easier for you to integrate into
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your applications.</para>
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<para>To assert your right to access and change data in an
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account, you identify yourself to Object Storage by using an
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authentication token. To get a token, you present your
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credentials to an authentication service. The authentication
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service returns a token and the URL for the account. Depending
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on which authentication service that you use, the URL for the
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account appears in:</para>
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<itemizedlist>
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<listitem>
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<para><emphasis role="bold">OpenStack Identity
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Service</emphasis>. The URL is defined in the
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service catalog.</para>
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</listitem>
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<listitem>
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<para><emphasis role="bold">Tempauth</emphasis>. The URL
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is provided in the <literal>X-Storage-Url</literal>
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response header.</para>
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</listitem>
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</itemizedlist>
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<para>In both cases, the URL is the full URL and includes the
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account resource. For information about authentication, see
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<xref linkend="authentication"/>.</para>
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<para>The Object Storage API supports the standard, non-serialized
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response format, which is the default, and both JSON and XML
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serialized response formats. See <xref
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linkend="serialized-response-formats"/>.</para>
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<para>The Object Storage system organizes data in a hierarchy, as
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follows:</para>
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<itemizedlist>
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<listitem>
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<para><emphasis role="bold">Account</emphasis>. Represents
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the top-level of the hierarchy.</para>
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<para>Your service provider creates your account and you
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own all resources in that account. The account defines
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a namespace for containers. A container might have the
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same name in two different accounts.</para>
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<para>In the OpenStack environment,
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<firstterm>account</firstterm> is synonymous with
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a project or tenant.</para>
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</listitem>
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<listitem>
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<para><emphasis role="bold">Container</emphasis>. Defines
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a namespace for objects. An object with the same name
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in two different containers represents two different
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objects. You can create any number of containers
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within an account.</para>
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<para>In addition to containing objects, you can also use
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the container to control access to objects by using an
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access control list (ACL). You cannot store an ACL
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with individual objects.</para>
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<para>In addition, you configure and control many other
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features, such as object versioning, at the container
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level. See <xref linkend="set-object-versions"
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/>.</para>
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<para>You can bulk-delete up to 10,000 containers in a
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single request. See <xref linkend="bulk-delete"
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/>.</para>
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</listitem>
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<listitem>
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<para><emphasis role="bold">Object</emphasis>. Stores data
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content, such as documents, images, and so on. You can
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also store custom metadata with an object.</para>
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<para>With the Object Storage API, you can:</para>
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<itemizedlist>
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<listitem>
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<para>Store an unlimited number of objects. Each
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object can be as large as 5 GB, which is the
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default. You can configure the maximum object
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size.</para>
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</listitem>
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<listitem>
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<para>Upload and store objects of any size with
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large object creation. See <xref
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linkend="large-object-creation"/>.</para>
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</listitem>
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<listitem>
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<para>Use cross-origin resource sharing to manage
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object security. See <xref
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linkend="cors-headers"/>.</para>
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</listitem>
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<listitem>
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<para>Compress files. See <xref
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linkend="file-compression"/>.</para>
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</listitem>
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<listitem>
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<para>Override browser behavior for an object. See
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<xref linkend="content-disposition"
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/>.</para>
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</listitem>
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<listitem>
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<para>Schedule objects for deletion. See <xref
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linkend="expire-objects"/>.</para>
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</listitem>
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<listitem>
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<para>Bulk-delete up to 10,000 objects in a single
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request. See <xref linkend="bulk-delete"
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/>.</para>
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</listitem>
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<listitem>
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<para>Auto-extract archive files. See <xref
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linkend="archive-auto-extract"/>.</para>
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</listitem>
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<listitem>
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<para>Generate a URL that provides time-limited
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&GET; access to an object. See <xref
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linkend="tempurl"/>.</para>
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</listitem>
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<listitem>
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<para>Upload objects directly to the Object
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Storage system from a browser by using form
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&POST; middleware. See <xref
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linkend="form-post"/>.</para>
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</listitem>
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</itemizedlist>
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</listitem>
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</itemizedlist>
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<para>The account, container, and object hierarchy affects the way
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you interact with the Object Storage API.</para>
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<para>Specifically, the resource path reflects this structure and
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has this format:</para>
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<programlisting>/v1/{account}/{container}/{object}</programlisting>
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<para>For example, for the <literal>flowers/rose.jpg</literal>
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object in the <literal>images</literal> container in the
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<literal>12345678912345</literal> account, the resource
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path is:</para>
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<programlisting>/v1/12345678912345/images/flowers/rose.jpg</programlisting>
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<para>Notice that the object name contains the
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<literal>/</literal> character. This slash does not
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indicate that Object Storage has a sub-hierarchy called
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<literal>flowers</literal> because containers do not store
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objects in actual sub-folders. However, the inclusion of
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<literal>/</literal> or a similar convention inside object
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names enables you to create pseudo-hierarchical folders and
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directories. See <xref
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linkend="pseudo-hierarchical-folders-directories"
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/>.</para>
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<para>For example, if the endpoint for Object Storage is
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<literal>objects.mycloud.com</literal>, the returned URL
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is
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<literal>https://objects.mycloud.com/v1/12345678912345</literal>.</para>
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<para>To access a container, append the container name to the
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resource path.</para>
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<para>To access an object, append the container and the object
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name to the path.</para>
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<para>If you have a large number of containers or objects, you can
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use query parameters to page through large lists of
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containers or objects. Use the <parameter>marker</parameter>,
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<parameter>limit</parameter>, and
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<parameter>end_marker</parameter> query parameters to
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control how many items are returned in a list and where the
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list starts or ends. See <xref linkend="large-lists"/>.</para>
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<para>Object Storage HTTP requests have the following default
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constraints. Your service provider might use different default
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values.</para>
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<informaltable rules="all">
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<thead>
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<tr>
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<th>Item</th>
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<th>Maximum value</th>
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<th>Notes</th>
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</tr>
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</thead>
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<tbody>
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<tr>
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<td>Number of HTTP headers</td>
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<td>90</td>
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<td/>
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</tr>
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<tr>
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<td>Length of HTTP headers</td>
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<td>4096 bytes</td>
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<td/>
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</tr>
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<tr>
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<td>Length per HTTP request line</td>
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<td>8192 bytes</td>
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<td/>
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</tr>
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<tr>
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<td>Length of HTTP request</td>
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<td>5 GB</td>
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<td/>
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</tr>
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<tr>
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<td>Length of container names</td>
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<td>256 bytes</td>
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<td>Cannot contain the <literal>/</literal>
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character.</td>
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</tr>
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<tr>
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<td>Length of object names</td>
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<td>1024 bytes</td>
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<td>By default, there are no character
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restrictions.</td>
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</tr>
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</tbody>
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</informaltable>
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<para>You must UTF-8-encode and then URL-encode container and
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object names before you call the API binding. If you use an
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API binding that performs the URL-encoding for you, do not
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URL-encode the names before you call the API binding.
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Otherwise, you double-encode these names. Check the length
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restrictions against the URL-encoded string.</para>
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<para>These sections describe the operations that you can perform
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with the Object Storage API:</para>
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<itemizedlist>
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<listitem>
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<para><xref linkend="storage_account_services"/>. Use to
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perform account-level tasks.</para>
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<para>Lists containers for a specified account. Creates,
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updates, and deletes account metadata. Shows account
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metadata.</para>
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</listitem>
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<listitem>
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<para><xref linkend="storage_container_services"/>. Use to
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perform container-level tasks.</para>
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<para>Lists objects in a specified container. Creates,
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shows details for, and deletes containers. Creates,
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updates, shows, and deletes container metadata.</para>
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</listitem>
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<listitem>
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<para><xref linkend="storage_object_services"/>. Use to
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perform object-level tasks.</para>
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<para>Creates, replaces, shows details for, and deletes
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objects. Copies objects with another object with a new
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or different name. Updates object metadata.</para>
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</listitem>
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</itemizedlist>
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</section>
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