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Ruby API for interacting with docker_registry v2 with support for token authentication

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Docker Registry

Introduction

This is a simple gem that provides direct http access to a docker registry v2 without going through a docker server. You do not require docker installed on your system to provide access.

reg = DockerRegistry2.connect("https://my.registy.corp.com")
repos = reg.search("foo/repo")
tags = reg.tags("foo/repo")

Supports anonymous access, http authorization and v2 token access.

Inspired by https://github.com/rosylilly/docker_registry but written separately.

Note

Prior to version 0.4.0, the name used was DockerRegistry. As of 0.4.0 it is DockerRegistry2. If you still need DockerRegistry, just create an alias with:

DockerRegistry = DockerRegistry2

Installation

Add the following to your Gemfile:

gem 'docker_registry2'

And execute:

bundle install

Usage

Once it is installed, you first open a connection to a registry, and then request from the registry.

Connecting

Use the connect method to connect to a registry:

reg = DockerRegistry2.connect("https://my.registy.corp.com")

If you do not provide the URL for a registry, it uses the default https://registry.hub.docker.com.

By default, requests to the registry will timeout if they take over 2 seconds to connect or over 5 seconds to respond. You can set different thresholds when connecting to a registry as follows:

opts = { open_timeout: 2, read_timeout: 5 }
reg = DockerRegistry2.connect("https://my.registy.corp.com", opts)

Your may pass extra options for RestClient::Request.execute through http_options :

opts = { http_options: { proxy: 'http://proxy.example.com:8080/' } }
reg = DockerRegistry2.connect("https://my.registy.corp.com", opts)

You can connect anonymously or with credentials:

Anonymous

To connect to a registry:

reg = DockerRegistry2.connect("https://my.registy.corp.com")

The above will connect anonymously to the registry via the endpoint https://my.registry.corp.com/v2/.

The following exceptions are thrown:

  • RegistryAuthenticationException: registry does not support anonymous access
  • RegistryUnknownException: registry does not exist at the given URL
  • RegistrySSLException: registry SSL certificate cannot be validated

Authenticated

If you wish to authenticate, pass a username and password as part of the options to DockerRegistry.connect.

url = "https://my.registy.corp.com"
opts = {user: "me", password: "secretstuff"}
reg = DockerRegistry2.connect(url,opts)

Note: Older versions prior to 1.0.0 used to support putting the username and password in the URL. We no longer support it as it is strongly discouraged in RFCs. Put it in the opts hash.

The following exceptions are thrown:

  • RegistryAuthenticationException: username/password combination is invalid
  • RegistryAuthorizationException: username/password does not have sufficient rights to access this registry
  • RegistryUnknownException: registry does not exist at the given URL
  • RegistrySSLException: registry SSL certificate cannot be validated

Requests

Once you have a valid reg object return by DockerRegistry2.connect(), you can make requests. As of this version, only search and tags are supported. Others will be added over time.

search

results = reg.search("mylibs")

Returns all repositories whose name contains "mylibs".

Note: The v2 registry does not support search directly server-side. Thus, this is simulated by using the catalog/ endpoint. It is highly recommended to avoid using this function until the v2 registry supports direct search, as it will be slow. It pulls a list of all repositories to the client and then does a pattern match on them.

Returns an array of strings, each of which is the full name of a repository.

If no results are found, will return an empty array []. An empty array will not throw an exception.

The following exceptions are thrown:

  • RegistryAuthenticationException: username and password are invalid
  • RegistryAuthorizationException: user does not have sufficient rights to search in this registry

NOTE: The search endpoint relies on the catalog endpoint, which only is available from registry:2.1. If you try it prior to 2.1, you will get a 404 error.

tags

results = reg.tags("mylibs",count=nil,last="",withHashes=false)

Returns all known tags for the repository precisely named "mylibs".

Arguments:

  • repository: name of the repository to return, e.g. "mylibs" above. Relative to the registry to which you connected. REQUIRED.
  • count: how many records to return, if the registry supports pagination. Default is not to limit. The behaviour changes by registry implementation. See the section on pagination below. OPTIONAL.
  • last: the last record returned, if using pagination. See the section on pagination below. OPTIONAL.
  • withHashes: return the hash of the manifest for each tag. Note that retrieving the hashes is an expensive operations, as it requires a separate HEAD for each tag. This is why the default is false. OPTIONAL.

Returns an object with the following key value pairs: array of objects, each of which has the following key/value pairs:

  • name: full name of repository, e.g. redis or user/redis.
  • tags: array of strings, each of which is a tag for ths given repository.
  • hashes: object, keys of which are the tag name, and values of which are the hash. Only provided if withHashes is true.
  • last: the last entry returned, to be used for pagination, only returned if the results have been paginated by the server.

Other fields may be added later. Do not assume those are the only fields.

If no tags are found, or the named repository does not exist, return an empty object {}. An unknown repository will not throw an exception.

The response structure looks something like this:

{
	"name" => "special/repo",
	"tags" => ["1.0","1.1","1.3","latest"],
	"hashes" => {
		"1.0" => "abc4567",
		"1.1" => "87def23",
		"1.3" => "998adf2",
		"latest" => "998adf2"
	}
}

It is important to note that the hashes may or may not match the hashes that you receive when running docker images on your machine. These are the hashes returned by the Docker-Content-Digest for the manifest. See v2 API Spec.

These may or may not be useful for comparing to the local image on disk when running docker images. These are useful for comparing 2 different tags or images in one or more registries.

The following exceptions are thrown:

  • RegistryAuthenticationException: username and password are invalid
  • RegistryAuthorizationException: registry does not support tags using the given credentials, probably because the repository is private and the credentials provided do not have access
pagination

Some regstries support pagination for tags per this standard. If the registry supports pagination, you have several options:

  • Ignore it, and simply get back whatever the max number o tags the registry returns in whatever order. In many cases, this will work. tags("repo")
  • Set an arbitrarily high number. Note that this may not work, as the registry may implement a limit below your cap. tags("repo", 5000)
  • Work with pagination.

To work with pagination, after each result set, you keep getting a new result set until there are no more. In this case, with each request, the tags() results will tell you what the key of the last one was returned. You pass that into the next call, so it knows where to start for the next set of results. You also can choose to limit the count, or just accept whatever default the registry has set.

For example, let us assume that the registry has 26 tags, from "a" to "z", and that it returns 3 tags with each call by default. Your first call:

res = tags("repo")
# or, to limit to 3 explicilty
res = tags("repo")

Your results will be:

{
        "name" => "repo",
        "tags" => ["a","b","c"],
	"last" => "c"
}

Note that it returned 3, either because that was the registry default or you explicitly limited to 3 results. It also told you that the last tag was "c". You now can pass that on to the next request.

res = tags("repo",nil,"c")
# or, to limit to 3 explicitly
res = tags("repo",3,"c")

The results will be:

{
        "name" => "repo",
        "tags" => ["d","e","f"]
        "last" => "f"
}

Repeat until you have all of the results. The last one has no more pagination, and so the results will be without a "last" field:

{
        "name" => "repo",
        "tags" => ["x","y","z"]
}

manifest

manifest = reg.manifest("namespace/repo","2.5.6")

Returns the manifest for the given tag of the given repository. For the format and syntax of the manifest, see the registry API and the manifest issue.

If the given repository and/or tag is not found, return an empty object {}.

The following exceptions are thrown:

  • RegistryAuthenticationException: username and password are invalid
  • RegistryAuthorizationException: registry does not support tags using the given credentials, probably because the repository is private and the credentials provided do not have access

The manifest, of course, is requested via http GET. While the returned manifest is an object parsed from the JSON of the manifest body, sometimes the http headers are valuable as well. Thus the returned manifest object has a method headers, which returns the http headers from the request.

manifest = reg.manifest("namespace/repo","2.5.6")
manifest.headers

blob

> blob_digest = "sha256:87fbbe5ed7a499baa6603cd81502cfe0f26d0e9fe8b2feca8bc4ab04cd87c01e"
> blob = reg.blob("namespace/repo", blob_digest, '/path/to/blob')

Returns the blob for the given digest in given repository. Blobs can vary in size, so a file path may be passed to stream the data. This is the recommended approach for downloading layer blobs due to their large size. For the format and syntax of the blob, see the registry API

The following exceptions are thrown:

  • RegistryAuthenticationException: username and password are invalid
  • RegistryAuthorizationException: registry does not support tags using the given
  • NotFound: Either the repo or blob cannot be found

Alternatively, if omitted the raw blob will be returned:

> blob = reg.blob("namespace/repo", "sha256:437f2acdb882407ad515c936c6f1cd9adbbb1340c8b271797723464c6ac71f9b")
> blob.headers
=> {:date=>"Sun, 01 Dec 2019 15:48:57 GMT", :content_type=>"application/octet-stream", :content_length=>"7016", :connection=>"keep-alive", :set_cookie=>["__cfduid=d7b1e0e004daa8e1ffd2c8c80c70959e51575215337; expires=Tue, 31-Dec-19 15:48:57 GMT; path=/; domain=.production.cloudflare.docker.com; HttpOnly; Secure"], :cf_ray=>"53e6355468b3e593-MAN", :cf_cache_status=>"HIT", :cache_control=>"public, max-age=14400", :accept_ranges=>"bytes", :age=>"990327", :etag=>"\"574739ff4eca4fe0b24bcac899909659\"", :expires=>"Sun, 01 Dec 2019 19:48:57 GMT", :last_modified=>"Wed, 20 Nov 2019 01:18:29 GMT", :vary=>"Accept-Encoding", :expect_ct=>"max-age=604800, report-uri=\"https://report-uri.cloudflare.com/cdn-cgi/beacon/expect-ct\"", :x_amz_id_2=>"nL/phq2BUYjsGIwrSHh8QMqsnGNbjDlDjFjunI7qOqpnfR/3WAbVnKcobw4d23+nAx3lAED6Vbw=", :x_amz_request_id=>"E6B231599CAE0074", :x_amz_version_id=>"hTvrmlz_ARV25b0tY5NVrEJNlv7._2J3", :server=>"cloudflare"}
> blob.body
=> "<raw body>"

The mediaType on the manifest paired with the digest determines the blob format, so in the case of an image blob (application/vnd.docker.distribution.manifest.v2+json) the body can be deserialized from JSON

> manifest = reg.manifest "library/nginx", "1.17.6-alpine"
=> {"schemaVersion"=>2, "mediaType"=>"application/vnd.docker.distribution.manifest.v2+json", "config"=>{"mediaType"=>"application/vnd.docker.container.image.v1+json", "size"=>7016, "digest"=>"sha256:a624d888d69ffdc185ed3b9c9c0645e8eaaac843ce59e89f1fbe45b0581e4ef6"}, "layers"=>[{"mediaType"=>"application/vnd.docker.image.rootfs.diff.tar.gzip", "size"=>2787134, "digest"=>"sha256:89d9c30c1d48bac627e5c6cb0d1ed1eec28e7dbdfbcc04712e4c79c0f83faf17"}, {"mediaType"=>"application/vnd.docker.image.rootfs.diff.tar.gzip", "size"=>5984561, "digest"=>"sha256:24f1c4f0b2f40c236ec9c306bd841778f30db9e6e7f067512732147ae7c11b07"}]}
> image_digest = manifest['config']['digest']
=> "sha256:a624d888d69ffdc185ed3b9c9c0645e8eaaac843ce59e89f1fbe45b0581e4ef6"
> raw_blob = reg.blob "library/nginx", image_digest
=> #<DockerRegistry2::Blob:0x007fd9bf8f2e10 ...>
> image_blob = JSON.parse(raw_blob.body)
=> {...}
> image_blob['architecture']
=> "amd64"
> image_blob['os']
=> "linux"
> image_blob['docker_version']
=> "18.06.1-ce"
> image_blob['created']
=> "2019-11-20T01:16:50.939316846Z"
> image_blob['config']['Labels']
=> {"maintainer"=>"NGINX Docker Maintainers <[email protected]>"}

digest

digest = reg.digest("namespace/repo", "2.5.6")

Returns the digest for the manifest represented by the tag of the given repository.

pull

reg.pull("namespace/repo","2.5.6",dir)

Pulls the given tag of the given repository to the given dir. If given dirdoes not exist, will create it.

It is important to note that the image for a tag is not likely to be a single file, but rather multiple layers, each of which is an individual file. Thus, it is necessary to have a directory where the downloaded layers are to be kept. The actual docker engine stores these under /var/lib/docker/.

If the given repository and/or tag is not found, return an empty object {}.

The following exceptions are thrown:

  • RegistryAuthenticationException: username and password are invalid
  • RegistryAuthorizationException: registry does not support tags or pull using the given credentials, probably because the repository is private and the credentials provided do not have access.

push

WARNING: Unimplemented

reg.push(manifest,dir)

Pushes the given manifest to the registry, using images in the given dir. You are assumed to have created the manifest or gotten it from somewhere else. This is especially useful for moving an image from one registry to another. You can get the manifest, pull the layers, and push the manifest to a different registry.

The following exceptions are thrown:

  • RegistryAuthenticationException: username and password are invalid
  • RegistryAuthorizationException: registry does not support pushing the layers or uploading the manifest using the given credentials, probably because the repository is private and the credentials provided do not have access
  • MissingLayerException: A layer from the manifest is missing from the given dir and thus cannot be pushed.

tag

reg.tag("namespace/repo","tag",newrepo,newtag)

tag is a convenience method to create a new repository for a given repository in the same registry. For example, you have a registry at https://my.registry.local. In the registry is a repository named "myspace/repo", with a tag "1.2". You wish to duplicate "myspace/repo:1.2" to "myspace/repo:latest". Or, perhaps you wish to duplicate "myspace/repo:1.2" to "others/image:10.5". You can do it using tag:

reg.tag("myspace/repo","1.2","myspace/repo","latest")
reg.tag("myspace/repo","1.2","other/image","10.5")

This is a convenience and efficiency method. Because it only manipulates the manifest, and not the layers (which already are present in the registry), it can do so quickly.

The following exceptions are thrown:

  • RegistryAuthenticationException: username and password are invalid
  • RegistryAuthorizationException: registry does not support pushing the layers or uploading the manifest using the given credentials, probably because the repository is private and the credentials provided do not have access
  • RegisteryVersionException: registry does not support the v2 API.

copy

WARNING: Unimplemented

reg.copy("namespace/repo","tag",newregistry,newrepo,newtag)

copy copies an image from one registry to another. It does so in the following manner:

  1. Download the manifest
  2. Download all relevant layers
  3. Modify the manifest as needed to reflect the newrepo and newtag
  4. Upload the layers to newregistry
  5. Upload the manifest to newregistry

The following exceptions are thrown:

  • RegistryAuthenticationException: username and password are invalid
  • RegistryAuthorizationException: registry does not support pushing the layers or uploading the manifest using the given credentials, probably because the repository is private and the credentials provided do not have access

rmtag

reg.rmtag("namespace/repo","tag")

rmtag removes a given tag from a repository.

The following exceptions are thrown:

  • RegistryAuthenticationException: username and password are invalid
  • RegistryAuthorizationException: registry does not support your deleting the given tag, probably because you do not have sufficient access rights.

rmrepo

reg.rmrepo("namespace/repo")

rmrepo removes the named repository entirely.

The following exceptions are thrown:

  • RegistryAuthenticationException: username and password are invalid
  • RegistryAuthorizationException: registry does not support your deleting the given repository, probably because you do not have sufficient access rights.

Layer sizes

If you want to get the sizes of one or more layers in an image, you have several convenience functions available.

Total Size

If you want to add up easily all of the layers in a manifest (which, of course, should equal the total size of the image), you can pass the manifest to the manifest_sum method.

manifest = reg.manifest "library/ubuntu", "16.04"
totalSize = reg.manifest_sum manifest
Single Blob

If you have the repo name and the sha256 hash for the blob, you can get the size of the layer by doing:

reg.blob_size "namespace/repo", "sha256:abc5634737434"

Of course, most of the time you won't need this, since the sizes are already included in the same place you got the blob hashes in the first place: the manifest.

Append a Tarball Layer to an Existing Repo

tarball_filepath = File.join(File.dirname(FILE ),'files', 'mydata.tgz')

@registry.append_blob(image_repo_name, "latest", tarball_filepath)

In this case, if mydata is a tar'd folder named mydata.tgz, if you pull the image, you should now see

/mydata/

Exceptions

All exceptions thrown inherit from DockerRegistry2::Exception.

Tests

The simplest way to test is against a true v2 registry. Thus, the test setup and teardown work against a docker registry. That means that to test, you need a docker engine running. The tests will start up a registry (actually, two registries, to be able to test copy()), initialize the data and test against them.

To run tests, simply run

bundle exec rspec spec

License

MIT License.

Contribution

Developed by Avi Deitcher http://github.com/deitch Contributors Jonathan Hurter https://github.com/johnsudaar Contributions courtesy of TraderTools, Inc. http://tradertools.com Contributions courtesy of BrowserUp, Inc. https://browserup.com

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Ruby API for interacting with docker_registry v2 with support for token authentication

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