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spec: fetch manifests by tag or digest
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Manifests are now fetched by a field called "reference", which may be a tag or
a digest. When using digests to reference a manifest, the data is immutable.
The routes and specification have been updated to allow this.

There are a few caveats to this approach:

1. It may be problematic to rely on data format to differentiate between a tag
   and a digest. Currently, they are disjoint but there may modifications on
   either side that break this guarantee.
2. The caching characteristics of returned content are very different for
   digest versus tag-based references. Digest urls can be cached forever while tag
   urls cannot.

Both of these are minimal caveats that we can live with in the future.

Signed-off-by: Stephen J Day <stephen.day@docker.com>
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79 changes: 56 additions & 23 deletions doc/spec/api.md
View file
Original file line number Diff line number Diff line change
Expand Up @@ -106,9 +106,20 @@ changes. Only non-conflicting additions should be made to the API and accepted
changes should avoid preventing future changes from happening.

This section should be updated when changes are made to the specification,
indicating what is different. Optionally, we may start marking parts of the specification to correspond with the versions enumerated here.
indicating what is different. Optionally, we may start marking parts of the
specification to correspond with the versions enumerated here.

<dl>
<dt>2.0.1</dt>
<dd>
<ul>
<li>Added support for immutable manifest references in manifest endpoints.</li>
<li>Deleting a manifest by tag has been deprecated.</li>
<li>Specified `Docker-Content-Digest` header for appropriate entities.</li>
<li>Added error code for unsupported operations.</li>
</ul>
</dd>

<dt>2.0</dt>
<dd>
This is the baseline specification.
Expand Down Expand Up @@ -235,10 +246,11 @@ the V2 registry API, keyed by their tarsum digest.
The image manifest can be fetched with the following url:

```
GET /v2/<name>/manifests/<tag>
GET /v2/<name>/manifests/<reference>
```

The "name" and "tag" parameter identify the image and are required.
The `name` and `reference` parameter identify the image and are required. The
reference may include a tag or digest.

A `404 Not Found` response will be returned if the image is unknown to the
registry. If the image exists and the response is successful, the image
Expand Down Expand Up @@ -330,6 +342,7 @@ http specification). The response will look as follows:
```
200 OK
Content-Length: <length of blob>
Docker-Content-Digest: <digest>
```

When this response is received, the client can assume that the layer is
Expand Down Expand Up @@ -509,10 +522,14 @@ will receive a `201 Created` response:
201 Created
Location: /v2/<name>/blobs/<tarsum>
Content-Length: 0
Docker-Content-Digest: <digest>
```

The `Location` header will contain the registry URL to access the accepted
layer file.
layer file. The `Docker-Content-Digest` header returns the canonical digest of
the uploaded blob which may differ from the provided digest. Most clients may
ignore the value but if it is used, the client should verify the value against
the uploaded blob data.

###### Digest Parameter

Expand Down Expand Up @@ -574,7 +591,7 @@ client must restart the upload process.
Once all of the layers for an image are uploaded, the client can upload the
image manifest. An image can be pushed using the following request format:

PUT /v2/<name>/manifests/<tag>
PUT /v2/<name>/manifests/<reference>

{
"name": <name>,
Expand All @@ -591,8 +608,8 @@ image manifest. An image can be pushed using the following request format:
...
}

The `name` and `tag` fields of the response body must match those specified in
the URL.
The `name` and `reference` fields of the response body must match those specified in
the URL. The `reference` field may be a "tag" or a "digest".

If there is a problem with pushing the manifest, a relevant 4xx response will
be returned with a JSON error message. Please see the _PUT Manifest section
Expand Down Expand Up @@ -641,13 +658,14 @@ reduce copying.

### Deleting an Image

An image may be deleted from the registry via its `name` and `tag`. A delete
may be issued with the following request format:
An image may be deleted from the registry via its `name` and `reference`. A
delete may be issued with the following request format:

DELETE /v2/<name>/manifests/<tag>
DELETE /v2/<name>/manifests/<reference>

If the image exists and has been successfully deleted, the following response
will be issued:
For deletes, `reference` *must* be a digest or the delete will fail. If the
image exists and has been successfully deleted, the following response will be
issued:

202 Accepted
Content-Length: None
Expand Down Expand Up @@ -677,9 +695,9 @@ A list of methods and URIs are covered in the table below:
-------|----|------|------------
| GET | `/v2/` | Base | Check that the endpoint implements Docker Registry API V2. |
| GET | `/v2/<name>/tags/list` | Tags | Fetch the tags under the repository identified by `name`. |
| GET | `/v2/<name>/manifests/<tag>` | Manifest | Fetch the manifest identified by `name` and `tag`. |
| PUT | `/v2/<name>/manifests/<tag>` | Manifest | Put the manifest identified by `name` and `tag`. |
| DELETE | `/v2/<name>/manifests/<tag>` | Manifest | Delete the manifest identified by `name` and `tag`. |
| GET | `/v2/<name>/manifests/<reference>` | Manifest | Fetch the manifest identified by `name` and `reference` where `reference` can be a tag or digest. |
| PUT | `/v2/<name>/manifests/<reference>` | Manifest | Put the manifest identified by `name` and `reference` where `reference` can be a tag or digest. |
| DELETE | `/v2/<name>/manifests/<reference>` | Manifest | Delete the manifest identified by `name` and `reference` where `reference` can be a tag or digest. |

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@tcnghia

tcnghia Mar 27, 2015

Contributor

@stevvooe this description conflicts with line 666(!) that reference must be a digest or the delete will fail.

Does this mean that it is not possible to delete tag?

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@stevvooe

stevvooe Mar 31, 2015

Author Collaborator

@tcnghia Yep.

To understand this, please try to describe what should be deleted when deleting a tag. There is more detail in the original PR for this, but the main issue is that a tag does not uniquely identify a resource.

Do you delete every manifest referenced by that tag?
Do you delete every tag object that carried that name?

It makes much more sense to make the delete specific.
| GET | `/v2/<name>/blobs/<digest>` | Blob | Retrieve the blob from the registry identified by `digest`. A `HEAD` request can also be issued to this endpoint to obtain resource information without receiving all data. |
| POST | `/v2/<name>/blobs/uploads/` | Intiate Blob Upload | Initiate a resumable blob upload. If successful, an upload location will be provided to complete the upload. Optionally, if the `digest` parameter is present, the request body will be used to complete the upload in a single request. |
| GET | `/v2/<name>/blobs/uploads/<uuid>` | Blob Upload | Retrieve status of upload identified by `uuid`. The primary purpose of this endpoint is to resolve the current status of a resumable upload. |
Expand All @@ -697,6 +715,7 @@ The error codes encountered via the API are enumerated in the following table:
|Code|Message|Description|
-------|----|------|------------
`UNKNOWN` | unknown error | Generic error returned when the error does not have an API classification.
`UNSUPPORTED` | The operation is unsupported. | The operation was unsupported due to a missing implementation or invalid set of parameters.
`UNAUTHORIZED` | access to the requested resource is not authorized | The access controller denied access for the operation on a resource. Often this will be accompanied by a 401 Unauthorized response status.
`DIGEST_INVALID` | provided digest did not match uploaded content | When a blob is uploaded, the registry will check that the content matches the digest provided by the client. The error may include a detail structure with the key "digest", including the invalid digest string. This error may also be returned when a manifest includes an invalid layer digest.
`SIZE_INVALID` | provided length did not match content length | When a layer is uploaded, the provided size will be checked against the uploaded content. If they do not match, this error will be returned.
Expand Down Expand Up @@ -933,12 +952,12 @@ Create, update and retrieve manifests.

#### GET Manifest

Fetch the manifest identified by `name` and `tag`.
Fetch the manifest identified by `name` and `reference` where `reference` can be a tag or digest.



```
GET /v2/<name>/manifests/<tag>
GET /v2/<name>/manifests/<reference>
Host: <registry host>
Authorization: <scheme> <token>
```
Expand All @@ -962,6 +981,7 @@ The following parameters should be specified on the request:

```
200 OK
Docker-Content-Digest: <digest>
Content-Type: application/json; charset=utf-8
{
Expand All @@ -979,8 +999,13 @@ Content-Type: application/json; charset=utf-8
}
```

The manifest idenfied by `name` and `tag`. The contents can be used to identify and resolve resources required to run the specified image.
The manifest idenfied by `name` and `reference`. The contents can be used to identify and resolve resources required to run the specified image.

The following headers will be returned with the response:

|Name|Description|
|----|-----------|
|`Docker-Content-Digest`|Digest of the targeted content for the request.|



Expand All @@ -1003,7 +1028,7 @@ Content-Type: application/json; charset=utf-8
}
```

The name or tag was invalid.
The name or reference was invalid.



Expand Down Expand Up @@ -1080,12 +1105,12 @@ The error codes that may be included in the response body are enumerated below:

#### PUT Manifest

Put the manifest identified by `name` and `tag`.
Put the manifest identified by `name` and `reference` where `reference` can be a tag or digest.



```
PUT /v2/<name>/manifests/<tag>
PUT /v2/<name>/manifests/<reference>
Host: <registry host>
Authorization: <scheme> <token>
Content-Type: application/json; charset=utf-8
Expand Down Expand Up @@ -1126,6 +1151,7 @@ The following parameters should be specified on the request:
202 Accepted
Location: <url>
Content-Length: 0
Docker-Content-Digest: <digest>
```

The manifest has been accepted by the registry and is stored under the specified `name` and `tag`.
Expand All @@ -1136,6 +1162,7 @@ The following headers will be returned with the response:
|----|-----------|
|`Location`|The canonical location url of the uploaded manifest.|
|`Content-Length`|The `Content-Length` header must be zero and the body must be empty.|
|`Docker-Content-Digest`|Digest of the targeted content for the request.|



Expand Down Expand Up @@ -1277,12 +1304,12 @@ The error codes that may be included in the response body are enumerated below:

#### DELETE Manifest

Delete the manifest identified by `name` and `tag`.
Delete the manifest identified by `name` and `reference` where `reference` can be a tag or digest.



```
DELETE /v2/<name>/manifests/<tag>
DELETE /v2/<name>/manifests/<reference>
Host: <registry host>
Authorization: <scheme> <token>
```
Expand Down Expand Up @@ -1456,6 +1483,7 @@ The following parameters should be specified on the request:
```
200 OK
Content-Length: <length>
Docker-Content-Digest: <digest>
Content-Type: application/octet-stream
<blob binary data>
Expand All @@ -1468,12 +1496,14 @@ The following headers will be returned with the response:
|Name|Description|
|----|-----------|
|`Content-Length`|The length of the requested blob content.|
|`Docker-Content-Digest`|Digest of the targeted content for the request.|

###### On Success: Temporary Redirect

```
307 Temporary Redirect
Location: <blob location>
Docker-Content-Digest: <digest>
```

The blob identified by `digest` is available at the provided location.
Expand All @@ -1483,6 +1513,7 @@ The following headers will be returned with the response:
|Name|Description|
|----|-----------|
|`Location`|The location where the layer should be accessible.|
|`Docker-Content-Digest`|Digest of the targeted content for the request.|



Expand Down Expand Up @@ -2345,6 +2376,7 @@ The following parameters should be specified on the request:
Location: <blob location>
Content-Range: <start of range>-<end of range, inclusive>
Content-Length: <length of chunk>
Docker-Content-Digest: <digest>
```

The upload has been completed and accepted by the registry. The canonical location will be available in the `Location` header.
Expand All @@ -2356,6 +2388,7 @@ The following headers will be returned with the response:
|`Location`||
|`Content-Range`|Range of bytes identifying the desired block of content represented by the body. Start must match the end of offset retrieved via status check. Note that this is a non-standard use of the `Content-Range` header.|
|`Content-Length`|Length of the chunk being uploaded, corresponding the length of the request body.|
|`Docker-Content-Digest`|Digest of the targeted content for the request.|



Expand Down
42 changes: 30 additions & 12 deletions doc/spec/api.md.tmpl
View file
Original file line number Diff line number Diff line change
Expand Up @@ -106,9 +106,20 @@ changes. Only non-conflicting additions should be made to the API and accepted
changes should avoid preventing future changes from happening.

This section should be updated when changes are made to the specification,
indicating what is different. Optionally, we may start marking parts of the specification to correspond with the versions enumerated here.
indicating what is different. Optionally, we may start marking parts of the
specification to correspond with the versions enumerated here.

<dl>
<dt>2.0.1</dt>
<dd>
<ul>
<li>Added support for immutable manifest references in manifest endpoints.</li>
<li>Deleting a manifest by tag has been deprecated.</li>
<li>Specified `Docker-Content-Digest` header for appropriate entities.</li>
<li>Added error code for unsupported operations.</li>
</ul>
</dd>

<dt>2.0</dt>
<dd>
This is the baseline specification.
Expand Down Expand Up @@ -235,10 +246,11 @@ the V2 registry API, keyed by their tarsum digest.
The image manifest can be fetched with the following url:

```
GET /v2/<name>/manifests/<tag>
GET /v2/<name>/manifests/<reference>
```

The "name" and "tag" parameter identify the image and are required.
The `name` and `reference` parameter identify the image and are required. The
reference may include a tag or digest.

A `404 Not Found` response will be returned if the image is unknown to the
registry. If the image exists and the response is successful, the image
Expand Down Expand Up @@ -330,6 +342,7 @@ http specification). The response will look as follows:
```
200 OK
Content-Length: <length of blob>
Docker-Content-Digest: <digest>
```

When this response is received, the client can assume that the layer is
Expand Down Expand Up @@ -509,10 +522,14 @@ will receive a `201 Created` response:
201 Created
Location: /v2/<name>/blobs/<tarsum>
Content-Length: 0
Docker-Content-Digest: <digest>
```

The `Location` header will contain the registry URL to access the accepted
layer file.
layer file. The `Docker-Content-Digest` header returns the canonical digest of
the uploaded blob which may differ from the provided digest. Most clients may
ignore the value but if it is used, the client should verify the value against
the uploaded blob data.

###### Digest Parameter

Expand Down Expand Up @@ -574,7 +591,7 @@ client must restart the upload process.
Once all of the layers for an image are uploaded, the client can upload the
image manifest. An image can be pushed using the following request format:

PUT /v2/<name>/manifests/<tag>
PUT /v2/<name>/manifests/<reference>

{
"name": <name>,
Expand All @@ -591,8 +608,8 @@ image manifest. An image can be pushed using the following request format:
...
}

The `name` and `tag` fields of the response body must match those specified in
the URL.
The `name` and `reference` fields of the response body must match those specified in
the URL. The `reference` field may be a "tag" or a "digest".

If there is a problem with pushing the manifest, a relevant 4xx response will
be returned with a JSON error message. Please see the _PUT Manifest section
Expand Down Expand Up @@ -641,13 +658,14 @@ reduce copying.

### Deleting an Image

An image may be deleted from the registry via its `name` and `tag`. A delete
may be issued with the following request format:
An image may be deleted from the registry via its `name` and `reference`. A
delete may be issued with the following request format:

DELETE /v2/<name>/manifests/<tag>
DELETE /v2/<name>/manifests/<reference>

If the image exists and has been successfully deleted, the following response
will be issued:
For deletes, `reference` *must* be a digest or the delete will fail. If the
image exists and has been successfully deleted, the following response will be
issued:

202 Accepted
Content-Length: None
Expand Down
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