Type Alias CheckpointSaveFn 

pub type CheckpointSaveFn<S> = Box<dyn Fn(Checkpoint<S>, TraceId) -> Pin<Box<dyn Future<Output = Result<(), CheckpointStoreError>> + Send>> + Send + Sync>;

Checkpoint 保存回调类型别名。

Aliased Type

pub struct CheckpointSaveFn<S>(/* private fields */);