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Chapter 4. Ceph Object Gateway and the Swift API

As a developer, you can use a RESTful application programming interface (API) that is compatible with the Swift API data access model. You can manage the buckets and objects stored in Red Hat Ceph Storage cluster through the Ceph Object Gateway.

The following table describes the support status for current Swift functional features:

Table 4.1. Features
FeatureStatusRemarks

Authentication

Supported

 

Get Account Metadata

Supported

No custom metadata

Swift ACLs

Supported

Supports a subset of Swift ACLs

List Containers

Supported

 

List Container’s Objects

Supported

 

Create Container

Supported

 

Delete Container

Supported

 

Get Container Metadata

Supported

 

Add/Update Container Metadata

Supported

 

Delete Container Metadata

Supported

 

Get Object

Supported

 

Create/Update an Object

Supported

 

Create Large Object

Supported

 

Delete Object

Supported

 

Copy Object

Supported

 

Get Object Metadata

Supported

 

Add/Update Object Metadata

Supported

 

Temp URL Operations

Supported

 

CORS

Not Supported

 

Expiring Objects

Supported

 

Object Versioning

Not Supported

 

Static Website

Not Supported

 

Prerequisites

  • A running Red Hat Ceph Storage cluster.
  • A RESTful client.

4.1. Swift API limitations

Important

The following limitations should be used with caution. There are implications related to your hardware selections, so you should always discuss these requirements with your Red Hat account team.

  • Maximum object size when using Swift API: 5GB
  • Maximum metadata size when using Swift API: There is no defined limit on the total size of user metadata that can be applied to an object, but a single HTTP request is limited to 16,000 bytes.

4.2. Create a Swift user

To test the Swift interface, create a Swift subuser. Creating a Swift user is a two-step process. The first step is to create the user. The second step is to create the secret key.

Note

In a multi-site deployment, always create a user on a host in the master zone of the master zone group.

Prerequisites

  • Installation of the Ceph Object Gateway.
  • Root-level access to the Ceph Object Gateway node.

Procedure

  1. Create the Swift user:

    Syntax

    radosgw-admin subuser create --uid=NAME --subuser=NAME:swift --access=full

    Replace NAME with the Swift user name, for example:

    Example

    [root@host01 ~]# radosgw-admin subuser create --uid=testuser --subuser=testuser:swift --access=full
{
    "user_id": "testuser",
    "display_name": "First User",
    "email": "",
    "suspended": 0,
    "max_buckets": 1000,
    "auid": 0,
    "subusers": [
        {
            "id": "testuser:swift",
            "permissions": "full-control"
        }
    ],
    "keys": [
        {
            "user": "testuser",
            "access_key": "O8JDE41XMI74O185EHKD",
            "secret_key": "i4Au2yxG5wtr1JK01mI8kjJPM93HNAoVWOSTdJd6"
        }
    ],
    "swift_keys": [
        {
            "user": "testuser:swift",
            "secret_key": "13TLtdEW7bCqgttQgPzxFxziu0AgabtOc6vM8DLA"
        }
    ],
    "caps": [],
    "op_mask": "read, write, delete",
    "default_placement": "",
    "placement_tags": [],
    "bucket_quota": {
        "enabled": false,
        "check_on_raw": false,
        "max_size": -1,
        "max_size_kb": 0,
        "max_objects": -1
    },
    "user_quota": {
        "enabled": false,
        "check_on_raw": false,
        "max_size": -1,
        "max_size_kb": 0,
        "max_objects": -1
    },
    "temp_url_keys": [],
    "type": "rgw"
}

  2. Create the secret key:

    Syntax

    radosgw-admin key create --subuser=NAME:swift --key-type=swift --gen-secret

    Replace NAME with the Swift user name, for example:

    Example

    [root@host01 ~]# radosgw-admin key create --subuser=testuser:swift --key-type=swift --gen-secret
{
    "user_id": "testuser",
    "display_name": "First User",
    "email": "",
    "suspended": 0,
    "max_buckets": 1000,
    "auid": 0,
    "subusers": [
        {
            "id": "testuser:swift",
            "permissions": "full-control"
        }
    ],
    "keys": [
        {
            "user": "testuser",
            "access_key": "O8JDE41XMI74O185EHKD",
            "secret_key": "i4Au2yxG5wtr1JK01mI8kjJPM93HNAoVWOSTdJd6"
        }
    ],
    "swift_keys": [
        {
            "user": "testuser:swift",
            "secret_key": "a4ioT4jEP653CDcdU8p4OuhruwABBRZmyNUbnSSt"
        }
    ],
    "caps": [],
    "op_mask": "read, write, delete",
    "default_placement": "",
    "placement_tags": [],
    "bucket_quota": {
        "enabled": false,
        "check_on_raw": false,
        "max_size": -1,
        "max_size_kb": 0,
        "max_objects": -1
    },
    "user_quota": {
        "enabled": false,
        "check_on_raw": false,
        "max_size": -1,
        "max_size_kb": 0,
        "max_objects": -1
    },
    "temp_url_keys": [],
    "type": "rgw"
}

4.3. Swift authenticating a user

To authenticate a user, make a request containing an X-Auth-User and a X-Auth-Key in the header.

Syntax

GET /auth HTTP/1.1
Host: swift.example.com
X-Auth-User: johndoe
X-Auth-Key: R7UUOLFDI2ZI9PRCQ53K

Example Response

HTTP/1.1 204 No Content
Date: Mon, 16 Jul 2012 11:05:33 GMT
Server: swift
X-Storage-Url: https://swift.example.com
X-Storage-Token: UOlCCC8TahFKlWuv9DB09TWHF0nDjpPElha0kAa
Content-Length: 0
Content-Type: text/plain; charset=UTF-8

Note

You can retrieve data about Ceph’s Swift-compatible service by executing GET requests using the X-Storage-Url value during authentication.

Additional Resources

4.4. Swift container operations

As a developer, you can perform container operations with the Swift application programming interface (API) through the Ceph Object Gateway. You can list, create, update, and delete containers. You can also add or update the container’s metadata.

Prerequisites

  • A running Red Hat Ceph Storage cluster.
  • A RESTful client.

4.4.1. Swift container operations

A container is a mechanism for storing data objects. An account can have many containers, but container names must be unique. This API enables a client to create a container, set access controls and metadata, retrieve a container’s contents, and delete a container. Since this API makes requests related to information in a particular user’s account, all requests in this API must be authenticated unless a container’s access control is deliberately made publicly accessible, that is, allows anonymous requests.

Note

The Amazon S3 API uses the term 'bucket' to describe a data container. When you hear someone refer to a 'bucket' within the Swift API, the term 'bucket' might be construed as the equivalent of the term 'container.'

One facet of object storage is that it does not support hierarchical paths or directories. Instead, it supports one level consisting of one or more containers, where each container might have objects. The RADOS Gateway’s Swift-compatible API supports the notion of 'pseudo-hierarchical containers', which is a means of using object naming to emulate a container, or directory hierarchy without actually implementing one in the storage system. You can name objects with pseudo-hierarchical names, for example, photos/buildings/empire-state.jpg, but container names cannot contain a forward slash (/) character.

Important

When uploading large objects to versioned Swift containers, use the --leave-segments option with the python-swiftclient utility. Not using --leave-segments overwrites the manifest file. Consequently, an existing object is overwritten, which leads to data loss.

4.4.2. Swift update a container’s Access Control List (ACL)

When a user creates a container, the user has read and write access to the container by default. To allow other users to read a container’s contents or write to a container, you must specifically enable the user. You can also specify * in the X-Container-Read or X-Container-Write settings, which effectively enables all users to either read from or write to the container. Setting * makes the container public. That is it enables anonymous users to either read from or write to the container.

Syntax

POST /API_VERSION/ACCOUNT/TENANT:CONTAINER HTTP/1.1
Host: FULLY_QUALIFIED_DOMAIN_NAME
X-Auth-Token: AUTH_TOKEN
X-Container-Read: *
X-Container-Write: UID1, UID2, UID3

Request Headers

X-Container-Read
Description
The user IDs with read permissions for the container.
Type
Comma-separated string values of user IDs.
Required
No
X-Container-Write
Description
The user IDs with write permissions for the container.
Type
Comma-separated string values of user IDs.
Required
No

4.4.3. Swift list containers

A GET request that specifies the API version and the account will return a list of containers for a particular user account. Since the request returns a particular user’s containers, the request requires an authentication token. The request cannot be made anonymously.

Syntax

GET /API_VERSION/ACCOUNT HTTP/1.1
Host: FULLY_QUALIFIED_DOMAIN_NAME
X-Auth-Token: AUTH_TOKEN

Request Parameters

limit
Description
Limits the number of results to the specified value.
Type
Integer
Valid Values
N/A
Required
Yes
format
Description
Limits the number of results to the specified value.
Type
Integer
Valid Values
json or xml
Required
No
marker
Description
Returns a list of results greater than the marker value.
Type
String
Valid Values
N/A
Required
No

The response contains a list of containers, or returns with an HTTP 204 response code.

Response Entities

account
Description
A list for account information.
Type
Container
container
Description
The list of containers.
Type
Container
name
Description
The name of a container.
Type
String
bytes
Description
The size of the container.
Type
Integer

4.4.4. Swift list a container’s objects

To list the objects within a container, make a GET request with the API version, account, and the name of the container. You can specify query parameters to filter the full list, or leave out the parameters to return a list of the first 10,000 object names stored in the container.

Syntax

GET /API_VERSION/TENANT:CONTAINER HTTP/1.1
Host: FULLY_QUALIFIED_DOMAIN_NAME
X-Auth-Token: AUTH_TOKEN

Request Parameters

format
Description
Limits the number of results to the specified value.
Type
Integer
Valid Values
json or xml
Required
No
prefix
Description
Limits the result set to objects beginning with the specified prefix.
Type
String
Valid Values
N/A
Required
No
marker
Description
Returns a list of results greater than the marker value.
Type
String
Valid Values
N/A
Required
No
limit
Description
Limits the number of results to the specified value.
Type
Integer
Valid Values
0 - 10,000
Required
No
delimiter
Description
The delimiter between the prefix and the rest of the object name.
Type
String
Valid Values
N/A
Required
No
path
Description
The pseudo-hierarchical path of the objects.
Type
String
Valid Values
N/A
Required
No

Response Entities

container
Description
The container.
Type
Container
object
Description
An object within the container.
Type
Container
name
Description
The name of an object within the container.
Type
String
hash
Description
A hash code of the object’s contents.
Type
String
last_modified
Description
The last time the object’s contents were modified.
Type
Date
content_type
Description
The type of content within the object.
Type
String

4.4.5. Swift create a container

To create a new container, make a PUT request with the API version, account, and the name of the new container. The container name must be unique, must not contain a forward-slash (/) character, and should be less than 256 bytes. You can include access control headers and metadata headers in the request. You can also include a storage policy identifying a key for a set of placement pools. For example, execute radosgw-admin zone get to see a list of available keys under placement_pools. A storage policy enables you to specify a special set of pools for the container, for example, SSD-based storage. The operation is idempotent. If you make a request to create a container that already exists, it will return with a HTTP 202 return code, but will not create another container.

Syntax

PUT /API_VERSION/ACCOUNT/TENANT:CONTAINER HTTP/1.1
Host: FULLY_QUALIFIED_DOMAIN_NAME
X-Auth-Token: AUTH_TOKEN
X-Container-Read: COMMA_SEPARATED_UIDS
X-Container-Write: COMMA_SEPARATED_UIDS
X-Container-Meta-KEY:VALUE
X-Storage-Policy: PLACEMENT_POOLS_KEY

Headers

X-Container-Read
Description
The user IDs with read permissions for the container.
Type
Comma-separated string values of user IDs.
Required
No
X-Container-Write
Description
The user IDs with write permissions for the container.
Type
Comma-separated string values of user IDs.
Required
No
X-Container-Meta-KEY
Description
A user-defined metadata key that takes an arbitrary string value.
Type
String
Required
No
X-Storage-Policy
Description
The key that identifies the storage policy under placement_pools for the Ceph Object Gateway. Execute radosgw-admin zone get for available keys.
Type
String
Required
No

If a container with the same name already exists, and the user is the container owner then the operation will succeed. Otherwise, the operation will fail.

HTTP Response

409
Status Code
BucketAlreadyExists
Description
The container already exists under a different user’s ownership.

4.4.6. Swift delete a container

To delete a container, make a DELETE request with the API version, account, and the name of the container. The container must be empty. If you’d like to check if the container is empty, execute a HEAD request against the container. Once you’ve successfully removed the container, you’ll be able to reuse the container name.

Syntax

DELETE /API_VERSION/ACCOUNT/TENANT:CONTAINER HTTP/1.1
Host: FULLY_QUALIFIED_DOMAIN_NAME
X-Auth-Token: AUTH_TOKEN

HTTP Response

204
Status Code
NoContent
Description
The container was removed.

4.4.7. Swift add or update the container metadata

To add metadata to a container, make a POST request with the API version, account, and container name. You must have write permissions on the container to add or update metadata.

Syntax

POST /API_VERSION/ACCOUNT/TENANT:CONTAINER HTTP/1.1
Host: FULLY_QUALIFIED_DOMAIN_NAME
X-Auth-Token: AUTH_TOKEN
X-Container-Meta-Color: red
X-Container-Meta-Taste: salty

Request Headers

X-Container-Meta-KEY
Description
A user-defined metadata key that takes an arbitrary string value.
Type
String
Required
No

4.5. Swift object operations

As a developer, you can perform object operations with the Swift application programming interface (API) through the Ceph Object Gateway. You can list, create, update, and delete objects. You can also add or update the object’s metadata.

Prerequisites

  • A running Red Hat Ceph Storage cluster.
  • A RESTful client.

4.5.1. Swift object operations

An object is a container for storing data and metadata. A container might have many objects, but the object names must be unique. This API enables a client to create an object, set access controls and metadata, retrieve an object’s data and metadata, and delete an object. Since this API makes requests related to information in a particular user’s account, all requests in this API must be authenticated. Unless the container or object’s access control is deliberately made publicly accessible, that is, allows anonymous requests.

4.5.2. Swift get an object

To retrieve an object, make a GET request with the API version, account, container, and object name. You must have read permissions on the container to retrieve an object within it.

Syntax

GET /API_VERSION/ACCOUNT/TENANT:CONTAINER/OBJECT HTTP/1.1
Host: FULLY_QUALIFIED_DOMAIN_NAME
X-Auth-Token: AUTH_TOKEN

Request Headers

range
Description
To retrieve a subset of an object’s contents, you can specify a byte range.
Type
Date
Required
No
If-Modified-Since
Description
Only copies if modified since the date and time of the source object’s last_modified attribute.
Type
Date
Required
No
If-Unmodified-Since
Description
Only copies if not modified since the date and time of the source object’s last_modified attribute.
Type
Date
Required
No
Copy-If-Match
Description
Copies only if the ETag in the request matches the source object’s ETag.
Type
ETag
Required
No
Copy-If-None-Match
Description
Copies only if the ETag in the request does not match the source object’s ETag.
Type
ETag
Required
No

Response Headers

Content-Range
Description
The range of the subset of object contents. Returned only if the range header field was specified in the request.

4.5.3. Swift create or update an object

To create a new object, make a PUT request with the API version, account, container name, and the name of the new object. You must have write permission on the container to create or update an object. The object name must be unique within the container. The PUT request is not idempotent, so if you do not use a unique name, the request will update the object. However, you can use pseudo-hierarchical syntax in the object name to distinguish it from another object of the same name if it is under a different pseudo-hierarchical directory. You can include access control headers and metadata headers in the request.

Syntax

PUT /API_VERSION/ACCOUNT/TENANT:CONTAINER HTTP/1.1
Host: FULLY_QUALIFIED_DOMAIN_NAME
X-Auth-Token: AUTH_TOKEN

Request Headers

ETag
Description
An MD5 hash of the object’s contents. Recommended.
Type
String
Valid Values
N/A
Required
No
Content-Type
Description
An MD5 hash of the object’s contents.
Type
String
Valid Values
N/A
Required
No
Transfer-Encoding
Description
Indicates whether the object is part of a larger aggregate object.
Type
String
Valid Values
chunked
Required
No

4.5.4. Swift delete an object

To delete an object, make a DELETE request with the API version, account, container, and object name. You must have write permissions on the container to delete an object within it. Once you’ve successfully deleted the object, you will be able to reuse the object name.

Syntax

DELETE /API_VERSION/ACCOUNT/TENANT:CONTAINER/OBJECT HTTP/1.1
Host: FULLY_QUALIFIED_DOMAIN_NAME
X-Auth-Token: AUTH_TOKEN

4.5.5. Swift copy an object

Copying an object allows you to make a server-side copy of an object, so that you do not have to download it and upload it under another container. To copy the contents of one object to another object, you can make either a PUT request or a COPY request with the API version, account, and the container name.

For a PUT request, use the destination container and object name in the request, and the source container and object in the request header.

For a Copy request, use the source container and object in the request, and the destination container and object in the request header. You must have write permission on the container to copy an object. The destination object name must be unique within the container. The request is not idempotent, so if you do not use a unique name, the request will update the destination object. You can use pseudo-hierarchical syntax in the object name to distinguish the destination object from the source object of the same name if it is under a different pseudo-hierarchical directory. You can include access control headers and metadata headers in the request.

Syntax

PUT /API_VERSION/ACCOUNT/TENANT:CONTAINER HTTP/1.1
X-Copy-From: TENANT:SOURCE_CONTAINER/SOURCE_OBJECT
Host: FULLY_QUALIFIED_DOMAIN_NAME
X-Auth-Token: AUTH_TOKEN

or alternatively:

Syntax

COPY /API_VERSION/ACCOUNT/TENANT:SOURCE_CONTAINER/SOURCE_OBJECT HTTP/1.1
Destination: TENANT:DEST_CONTAINER/DEST_OBJECT

Request Headers

X-Copy-From
Description
Used with a PUT request to define the source container/object path.
Type
String
Required
Yes, if using PUT.
Destination
Description
Used with a COPY request to define the destination container/object path.
Type
String
Required
Yes, if using COPY.
If-Modified-Since
Description
Only copies if modified since the date and time of the source object’s last_modified attribute.
Type
Date
Required
No
If-Unmodified-Since
Description
Only copies if not modified since the date and time of the source object’s last_modified attribute.
Type
Date
Required
No
Copy-If-Match
Description
Copies only if the ETag in the request matches the source object’s ETag.
Type
ETag
Required
No
Copy-If-None-Match
Description
Copies only if the ETag in the request does not match the source object’s ETag.
Type
ETag
Required
No

4.5.6. Swift get object metadata

To retrieve an object’s metadata, make a HEAD request with the API version, account, container, and object name. You must have read permissions on the container to retrieve metadata from an object within the container. This request returns the same header information as the request for the object itself, but it does not return the object’s data.

Syntax

HEAD /API_VERSION/ACCOUNT/TENANT:CONTAINER/OBJECT HTTP/1.1
Host: FULLY_QUALIFIED_DOMAIN_NAME
X-Auth-Token: AUTH_TOKEN

4.5.7. Swift add or update object metadata

To add metadata to an object, make a POST request with the API version, account, container, and object name. You must have write permissions on the parent container to add or update metadata.

Syntax

POST /API_VERSION/ACCOUNT/TENANT:CONTAINER/OBJECT HTTP/1.1
Host: FULLY_QUALIFIED_DOMAIN_NAME
X-Auth-Token: AUTH_TOKEN

Request Headers

X-Object-Meta-KEY
Description
A user-defined meta data key that takes an arbitrary string value.
Type
String
Required
No

4.6. Swift temporary URL operations

To allow temporary access, temp url functionality is supported by swift endpoint of radosgw. For example GET requests, to objects without the need to share credentials.

For this functionality, initially the value of X-Account-Meta-Temp-URL-Key and optionally X-Account-Meta-Temp-URL-Key-2 should be set. The Temp URL functionality relies on a HMAC-SHA1 signature against these secret keys.

4.7. Swift get temporary URL objects

Temporary URL uses a cryptographic HMAC-SHA1 signature, which includes the following elements:

  • The value of the Request method, "GET" for instance
  • The expiry time, in the format of seconds since the epoch, that is, Unix time
  • The request path starting from "v1" onwards

The above items are normalized with newlines appended between them, and a HMAC is generated using the SHA-1 hashing algorithm against one of the Temp URL Keys posted earlier.

A sample python script to demonstrate the above is given below:

Example

import hmac
from hashlib import sha1
from time import time

method = 'GET'
host = 'https://objectstore.example.com'
duration_in_seconds = 300  # Duration for which the url is valid
expires = int(time() + duration_in_seconds)
path = '/v1/your-bucket/your-object'
key = 'secret'
hmac_body = '%s\n%s\n%s' % (method, expires, path)
hmac_body = hmac.new(key, hmac_body, sha1).hexdigest()
sig = hmac.new(key, hmac_body, sha1).hexdigest()
rest_uri = "{host}{path}?temp_url_sig={sig}&temp_url_expires={expires}".format(
     host=host, path=path, sig=sig, expires=expires)
print rest_uri

Example Output

https://objectstore.example.com/v1/your-bucket/your-object?temp_url_sig=ff4657876227fc6025f04fcf1e82818266d022c6&temp_url_expires=1423200992

4.8. Swift POST temporary URL keys

A POST request to the swift account with the required Key will set the secret temp URL key for the account against which temporary URL access can be provided to accounts. Up to two keys are supported, and signatures are checked against both the keys, if present, so that keys can be rotated without invalidating the temporary URLs.

Syntax

POST /API_VERSION/ACCOUNT HTTP/1.1
Host: FULLY_QUALIFIED_DOMAIN_NAME
X-Auth-Token: AUTH_TOKEN

Request Headers

X-Account-Meta-Temp-URL-Key
Description
A user-defined key that takes an arbitrary string value.
Type
String
Required
Yes
X-Account-Meta-Temp-URL-Key-2
Description
A user-defined key that takes an arbitrary string value.
Type
String
Required
No

4.9. Swift multi-tenancy container operations

When a client application accesses containers, it always operates with credentials of a particular user. In Red Hat Ceph Storage cluster, every user belongs to a tenant. Consequently, every container operation has an implicit tenant in its context if no tenant is specified explicitly. Thus multi-tenancy is completely backward compatible with previous releases, as long as the referred containers and referring user belong to the same tenant.

Extensions employed to specify an explicit tenant differ according to the protocol and authentication system used.

A colon character separates tenant and container, thus a sample URL would be:

Example

https://rgw.domain.com/tenant:container

By contrast, in a create_container() method, simply separate the tenant and container in the container method itself:

Example

create_container("tenant:container")

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