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author | Zeger-Jan van de Weg <git@zjvandeweg.nl> | 2018-12-03 16:49:58 +0300 |
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committer | Zeger-Jan van de Weg <git@zjvandeweg.nl> | 2018-12-07 21:18:37 +0300 |
commit | 896c0bdbfb1a83ff5a7d0a755ac249ac2a895798 (patch) | |
tree | 7f763bf296fe45d9a5bfa5c84164b2f4b06bda35 /lib/gitlab/git | |
parent | 498e34c6a4c990ae7d90b2d09cf4e73b9f228e13 (diff) |
Allow public forks to be deduplicated
When a project is forked, the new repository used to be a deep copy of everything
stored on disk by leveraging `git clone`. This works well, and makes isolation
between repository easy. However, the clone is at the start 100% the same as the
origin repository. And in the case of the objects in the object directory, this
is almost always going to be a lot of duplication.
Object Pools are a way to create a third repository that essentially only exists
for its 'objects' subdirectory. This third repository's object directory will be
set as alternate location for objects. This means that in the case an object is
missing in the local repository, git will look in another location. This other
location is the object pool repository.
When Git performs garbage collection, it's smart enough to check the
alternate location. When objects are duplicated, it will allow git to
throw one copy away. This copy is on the local repository, where to pool
remains as is.
These pools have an origin location, which for now will always be a
repository that itself is not a fork. When the root of a fork network is
forked by a user, the fork still clones the full repository. Async, the
pool repository will be created.
Either one of these processes can be done earlier than the other. To
handle this race condition, the Join ObjectPool operation is
idempotent. Given its idempotent, we can schedule it twice, with the
same effect.
To accommodate the holding of state two migrations have been added.
1. Added a state column to the pool_repositories column. This column is
managed by the state machine, allowing for hooks on transitions.
2. pool_repositories now has a source_project_id. This column in
convenient to have for multiple reasons: it has a unique index allowing
the database to handle race conditions when creating a new record. Also,
it's nice to know who the host is. As that's a short link to the fork
networks root.
Object pools are only available for public project, which use hashed
storage and when forking from the root of the fork network. (That is,
the project being forked from itself isn't a fork)
In this commit message I use both ObjectPool and Pool repositories,
which are alike, but different from each other. ObjectPool refers to
whatever is on the disk stored and managed by Gitaly. PoolRepository is
the record in the database.
Diffstat (limited to 'lib/gitlab/git')
-rw-r--r-- | lib/gitlab/git/object_pool.rb | 62 | ||||
-rw-r--r-- | lib/gitlab/git/repository.rb | 7 |
2 files changed, 69 insertions, 0 deletions
diff --git a/lib/gitlab/git/object_pool.rb b/lib/gitlab/git/object_pool.rb new file mode 100644 index 00000000000..558699a6318 --- /dev/null +++ b/lib/gitlab/git/object_pool.rb @@ -0,0 +1,62 @@ +# frozen_string_literal: true + +module Gitlab + module Git + class ObjectPool + # GL_REPOSITORY has to be passed for Gitlab::Git::Repositories, but not + # used for ObjectPools. + GL_REPOSITORY = "" + + delegate :exists?, :size, to: :repository + delegate :delete, to: :object_pool_service + + attr_reader :storage, :relative_path, :source_repository + + def initialize(storage, relative_path, source_repository) + @storage = storage + @relative_path = relative_path + @source_repository = source_repository + end + + def create + object_pool_service.create(source_repository) + end + + def link(to_link_repo) + remote_name = to_link_repo.object_pool_remote_name + repository.set_config( + "remote.#{remote_name}.url" => relative_path_to(to_link_repo.relative_path), + "remote.#{remote_name}.tagOpt" => "--no-tags", + "remote.#{remote_name}.fetch" => "+refs/*:refs/remotes/#{remote_name}/*" + ) + + object_pool_service.link_repository(to_link_repo) + end + + def gitaly_object_pool + Gitaly::ObjectPool.new(repository: to_gitaly_repository) + end + + def to_gitaly_repository + Gitlab::GitalyClient::Util.repository(storage, relative_path, GL_REPOSITORY) + end + + # Allows for reusing other RPCs by 'tricking' Gitaly to think its a repository + def repository + @repository ||= Gitlab::Git::Repository.new(storage, relative_path, GL_REPOSITORY) + end + + private + + def object_pool_service + @object_pool_service ||= Gitlab::GitalyClient::ObjectPoolService.new(self) + end + + def relative_path_to(pool_member_path) + pool_path = Pathname.new("#{relative_path}#{File::SEPARATOR}") + + Pathname.new(pool_member_path).relative_path_from(pool_path).to_s + end + end + end +end diff --git a/lib/gitlab/git/repository.rb b/lib/gitlab/git/repository.rb index 0a541031884..5bbedc9d5e3 100644 --- a/lib/gitlab/git/repository.rb +++ b/lib/gitlab/git/repository.rb @@ -69,6 +69,13 @@ module Gitlab attr_reader :storage, :gl_repository, :relative_path + # This remote name has to be stable for all types of repositories that + # can join an object pool. If it's structure ever changes, a migration + # has to be performed on the object pools to update the remote names. + # Else the pool can't be updated anymore and is left in an inconsistent + # state. + alias_method :object_pool_remote_name, :gl_repository + # This initializer method is only used on the client side (gitlab-ce). # Gitaly-ruby uses a different initializer. def initialize(storage, relative_path, gl_repository) |