To make the definition of supported digests more clear, we have refactored the
digest package to have a special Algorithm type. This represents the digest's
prefix and we associated various supported hash implementations through
function calls.
Signed-off-by: Stephen J Day <stephen.day@docker.com>
The change relies on a refactor of the upstream resumable sha256/sha512 package
that opts to register implementations with the standard library. This allows
the resumable support to be detected where it matters, avoiding unnecessary and
complex code. It also ensures that consumers of the digest package don't need
to depend on the forked sha implementations.
We also get an optimization with this change. If the size of data written to a
digester is the same as the file size, we check to see if the digest has been
verified. This works if the blob is written and committed in a single request.
Signed-off-by: Stephen J Day <stephen.day@docker.com>
This PR refactors the blob service API to be oriented around blob descriptors.
Identified by digests, blobs become an abstract entity that can be read and
written using a descriptor as a handle. This allows blobs to take many forms,
such as a ReadSeekCloser or a simple byte buffer, allowing blob oriented
operations to better integrate with blob agnostic APIs (such as the `io`
package). The error definitions are now better organized to reflect conditions
that can only be seen when interacting with the blob API.
The main benefit of this is to separate the much smaller metadata from large
file storage. Many benefits also follow from this. Reading and writing has
been separated into discrete services. Backend implementation is also
simplified, by reducing the amount of metadata that needs to be picked up to
simply serve a read. This also improves cacheability.
"Opening" a blob simply consists of an access check (Stat) and a path
calculation. Caching is greatly simplified and we've made the mapping of
provisional to canonical hashes a first-class concept. BlobDescriptorService
and BlobProvider can be combined in different ways to achieve varying effects.
Recommend Review Approach
-------------------------
This is a very large patch. While apologies are in order, we are getting a
considerable amount of refactoring. Most changes follow from the changes to
the root package (distribution), so start there. From there, the main changes
are in storage. Looking at (*repository).Blobs will help to understand the how
the linkedBlobStore is wired. One can explore the internals within and also
branch out into understanding the changes to the caching layer. Following the
descriptions below will also help to guide you.
To reduce the chances for regressions, it was critical that major changes to
unit tests were avoided. Where possible, they are left untouched and where
not, the spirit is hopefully captured. Pay particular attention to where
behavior may have changed.
Storage
-------
The primary changes to the `storage` package, other than the interface
updates, were to merge the layerstore and blobstore. Blob access is now
layered even further. The first layer, blobStore, exposes a global
`BlobStatter` and `BlobProvider`. Operations here provide a fast path for most
read operations that don't take access control into account. The
`linkedBlobStore` layers on top of the `blobStore`, providing repository-
scoped blob link management in the backend. The `linkedBlobStore` implements
the full `BlobStore` suite, providing access-controlled, repository-local blob
writers. The abstraction between the two is slightly broken in that
`linkedBlobStore` is the only channel under which one can write into the global
blob store. The `linkedBlobStore` also provides flexibility in that it can act
over different link sets depending on configuration. This allows us to use the
same code for signature links, manifest links and blob links. Eventually, we
will fully consolidate this storage.
The improved cache flow comes from the `linkedBlobStatter` component
of `linkedBlobStore`. Using a `cachedBlobStatter`, these combine together to
provide a simple cache hierarchy that should streamline access checks on read
and write operations, or at least provide a single path to optimize. The
metrics have been changed in a slightly incompatible way since the former
operations, Fetch and Exists, are no longer relevant.
The fileWriter and fileReader have been slightly modified to support the rest
of the changes. The most interesting is the removal of the `Stat` call from
`newFileReader`. This was the source of unnecessary round trips that were only
present to look up the size of the resulting reader. Now, one must simply pass
in the size, requiring the caller to decide whether or not the `Stat` call is
appropriate. In several cases, it turned out the caller already had the size
already. The `WriterAt` implementation has been removed from `fileWriter`,
since it is no longer required for `BlobWriter`, reducing the number of paths
which writes may take.
Cache
-----
Unfortunately, the `cache` package required a near full rewrite. It was pretty
mechanical in that the cache is oriented around the `BlobDescriptorService`
slightly modified to include the ability to set the values for individual
digests. While the implementation is oriented towards caching, it can act as a
primary store. Provisions are in place to have repository local metadata, in
addition to global metadata. Fallback is implemented as a part of the storage
package to maintain this flexibility.
One unfortunate side-effect is that caching is now repository-scoped, rather
than global. This should have little effect on performance but may increase
memory usage.
Handlers
--------
The `handlers` package has been updated to leverage the new API. For the most
part, the changes are superficial or mechanical based on the API changes. This
did expose a bug in the handling of provisional vs canonical digests that was
fixed in the unit tests.
Configuration
-------------
One user-facing change has been made to the configuration and is updated in
the associated documentation. The `layerinfo` cache parameter has been
deprecated by the `blobdescriptor` cache parameter. Both are equivalent and
configuration files should be backward compatible.
Notifications
-------------
Changes the `notification` package are simply to support the interface
changes.
Context
-------
A small change has been made to the tracing log-level. Traces have been moved
from "info" to "debug" level to reduce output when not needed.
Signed-off-by: Stephen J Day <stephen.day@docker.com>
- Set an Etag header
- Check If-None-Match and respond appropriately
- Set a Cache-Control header with a default of 1 week
Signed-off-by: Richard Scothern <richard.scothern@gmail.com>
- Ensures new uploads and resumed upload statuses always return an offset of 0. This allows future clients which support resumable upload to not attempt resumable upload on this version which does not support it.
- Add PATCH support for streaming data on upload.
- Add messaging to specification that PATCH with content range is currently not supported.
- Update PUT blob to only support full data or no data, no more last chunk messaging as it was not supported.
closes#470
Signed-off-by: Derek McGowan <derek@mcgstyle.net> (github: dmcgowan)
This changeset implements immutable manifest references via the HTTP API. Most
of the changes follow from modifications to ManifestService. Once updates were
made across the repo to implement these changes, the http handlers were change
accordingly. The new methods on ManifestService will be broken out into a
tagging service in a later PR.
Unfortunately, due to complexities around managing the manifest tag index in an
eventually consistent manner, direct deletes of manifests have been disabled.
Signed-off-by: Stephen J Day <stephen.day@docker.com>
This changeset adds support for a header to identify docker upload uuids. This
id can be used as a key to manage local state for resumable uploads. The goal
is remove the necessity for a client to parse the url to get an upload uuid.
The restrictions for clients to use the location header are still strongly in
place.
Signed-off-by: Stephen J Day <stephen.day@docker.com>
This change is slightly more complex than previous package maves in that the
package name changed. To address this, we simply always reference the package
driver as storagedriver to avoid compatbility issues with existing code. While
unfortunate, this can be cleaned up over time.
Signed-off-by: Stephen J Day <stephen.day@docker.com>
The goal is to free up the distribution/registry package to include common
registry types. This moves the webapp definitions out of the way to allow for
this change in the future.
Signed-off-by: Stephen J Day <stephen.day@docker.com>
