Trait Cas

pub trait Cas: Sync + Send {
    // Required methods
    fn current<'life0, 'async_trait>(
        &'life0 self,
    ) -> Pin<Box<dyn Future<Output = Result<Option<Vec<u8>>, Error>> + Send + 'async_trait>>
       where Self: 'async_trait,
             'life0: 'async_trait;
    fn swap<'life0, 'async_trait>(
        &'life0 self,
        value: Vec<u8>,
    ) -> Pin<Box<dyn Future<Output = Result<(), SwapError>> + Send + 'async_trait>>
       where Self: 'async_trait,
             'life0: 'async_trait;
    fn bucket_rep<'life0, 'async_trait>(
        &'life0 self,
    ) -> Pin<Box<dyn Future<Output = u32> + Send + 'async_trait>>
       where Self: 'async_trait,
             'life0: 'async_trait;
    fn key<'life0, 'async_trait>(
        &'life0 self,
    ) -> Pin<Box<dyn Future<Output = String> + Send + 'async_trait>>
       where Self: 'async_trait,
             'life0: 'async_trait;
}

Cas trait describes the interface a key value compare and swap implementor must fulfill.

current is expected to get the current value for the key associated with the CAS operation while also starting what is needed to ensure the value to be replaced will not have mutated between the time of calling current and swap. For example, a get from a backend store may provide the caller with an etag (a version stamp), which can be used with an if-match header to ensure the version updated is the version that was read (optimistic concurrency). Rather than an etag, one could start a transaction, if supported by the backing store, which would provide atomicity.

swap is expected to replace the old value with the new value respecting the atomicity of the operation. If there was no key / value with the given key in the store, the swap operation should insert the key and value, disallowing an update.

Required Methods

fn current<'life0, 'async_trait>( &'life0 self, ) -> Pin<Box<dyn Future<Output = Result<Option<Vec<u8>>, Error>> + Send + 'async_trait>>

where Self: 'async_trait, 'life0: 'async_trait,

fn swap<'life0, 'async_trait>( &'life0 self, value: Vec<u8>, ) -> Pin<Box<dyn Future<Output = Result<(), SwapError>> + Send + 'async_trait>>

where Self: 'async_trait, 'life0: 'async_trait,

fn bucket_rep<'life0, 'async_trait>( &'life0 self, ) -> Pin<Box<dyn Future<Output = u32> + Send + 'async_trait>>

where Self: 'async_trait, 'life0: 'async_trait,

fn key<'life0, 'async_trait>( &'life0 self, ) -> Pin<Box<dyn Future<Output = String> + Send + 'async_trait>>

where Self: 'async_trait, 'life0: 'async_trait,

Implementors