Struct git_repository::EasyArcExclusive

pub struct EasyArcExclusive {
    pub repo: Arc<RwLock<Repository>>,
    pub state: State,
}

A handle to a optionally mutable Repository for use in long-running applications that eventually need to update the Repository to adapt to changes they triggered or that were caused by other processes.

Using it incurs costs as each Repository access has to go through an indirection and involve an eventually fair RwLock. However, it’s vital to precisely updating the Repository instance as opposed to creating a new one while serving other requests on an old instance, which potentially duplicates the resource costs.

Limitation

• It can take a long time to get a mutable repo….
  • Imagine a typical server operation where a pack is sent to a client. As it’s a fresh clone it takes 5 minutes. Right after the clone began somebody initiates a push. Everything goes well and as a new pack was created the server wants to tell the object database to update its packs, making the new one available. To do that, it needs mutable access to the repository instance, and obtaining it will take until the end of the ongoing clone as the latter has acquired read-access to the same repository instance. This is most certainly undesirable.
  • Workarounds would be to
    • acquire the read-lock each time the clone operation wants to access an object
    • set a flag that triggers the server to create a new Repository instance next time a connection comes in which is subsequently shared across additional connections.
    • Create a new Repository per connection.

Fields

repo: Arc<RwLock<Repository>>

The repository

state: State

The state with interior mutability

Trait Implementations

impl Access for EasyArcExclusive

type RepoRef = ArcRwLockReadGuard<RawRwLock, Repository>

The type of a shared borrow to the Repository

type RepoRefMut = ArcRwLockWriteGuard<RawRwLock, Repository>

The type of a mutable borrow to the Repository

fn repo(&self) -> Result<Self::RepoRef, Error>

Return a shared borrow to the repository.

fn repo_mut(&self) -> Result<Self::RepoRefMut, Error>

Returns a mutable borrow to the repository if possible.

fn state(&self) -> &State

Return a shared borrow of the repository state, with support for interior mutability.

impl Clone for EasyArcExclusive

fn clone(&self) -> EasyArcExclusive

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl From<Repository> for EasyArcExclusive

fn from(repo: Repository) -> Self

Performs the conversion.