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CacheBackend

tower_http_cache::backend

Trait CacheBackend 

Source 
pub trait CacheBackend:
    Send
    + Sync
    + Clone
    + 'static {
    // Required methods
    fn get(
        &self,
        key: &str,
    ) -> impl Future<Output = Result<Option<CacheRead>, CacheError>> + Send;
    fn set(
        &self,
        key: String,
        entry: CacheEntry,
        ttl: Duration,
        stale_for: Duration,
    ) -> impl Future<Output = Result<(), CacheError>> + Send;
    fn invalidate(
        &self,
        key: &str,
    ) -> impl Future<Output = Result<(), CacheError>> + Send;

    // Provided methods
    fn get_keys_by_tag(
        &self,
        _tag: &str,
    ) -> impl Future<Output = Result<Vec<String>, CacheError>> + Send { ... }
    fn invalidate_by_tag(
        &self,
        tag: &str,
    ) -> impl Future<Output = Result<usize, CacheError>> + Send { ... }
    fn invalidate_by_tags(
        &self,
        tags: &[String],
    ) -> impl Future<Output = Result<usize, CacheError>> + Send { ... }
    fn list_tags(
        &self,
    ) -> impl Future<Output = Result<Vec<String>, CacheError>> + Send { ... }
}
Expand description

Storage a CacheLayer can read and write.

Every method returns impl Future<..> + Send rather than being an async fn. The + Send is required because the cache layer boxes backend futures into a Send future; a bare async fn in a trait does not guarantee it at the bound site.

Implementing this trait is unaffected by that. Write plain async fn in your impl block, with no #[async_trait] attribute:

#[derive(Clone)]
struct MyBackend;

impl CacheBackend for MyBackend {
    async fn get(&self, _key: &str) -> Result<Option<CacheRead>, CacheError> {
        Ok(None)
    }
    async fn set(
        &self,
        _key: String,
        _entry: CacheEntry,
        _ttl: Duration,
        _stale_for: Duration,
    ) -> Result<(), CacheError> {
        Ok(())
    }
    async fn invalidate(&self, _key: &str) -> Result<(), CacheError> {
        Ok(())
    }
}

Required Methods§

Source

fn get( &self, key: &str, ) -> impl Future<Output = Result<Option<CacheRead>, CacheError>> + Send

Fetches a cached entry by key.

Returns Ok(None) when the backend does not have a value or the entry has expired.

Source

fn set( &self, key: String, entry: CacheEntry, ttl: Duration, stale_for: Duration, ) -> impl Future<Output = Result<(), CacheError>> + Send

Stores an entry with a time-to-live and additional stale window.

Source

fn invalidate( &self, key: &str, ) -> impl Future<Output = Result<(), CacheError>> + Send

Invalidates the cache entry for key, if present.

Provided Methods§

Source

fn get_keys_by_tag( &self, _tag: &str, ) -> impl Future<Output = Result<Vec<String>, CacheError>> + Send

Retrieves all cache keys associated with a tag.

Returns an empty vector if tags are not supported by this backend.

Source

fn invalidate_by_tag( &self, tag: &str, ) -> impl Future<Output = Result<usize, CacheError>> + Send

Invalidates all cache entries associated with a tag.

Returns the number of entries invalidated.

Source

fn invalidate_by_tags( &self, tags: &[String], ) -> impl Future<Output = Result<usize, CacheError>> + Send

Invalidates all cache entries associated with multiple tags.

Returns the total number of entries invalidated (may include duplicates).

Source

fn list_tags( &self, ) -> impl Future<Output = Result<Vec<String>, CacheError>> + Send

Lists all currently indexed tags.

Returns an empty vector if tags are not supported by this backend.

Dyn Compatibility§

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety".

Implementors§