kash

Caching structures and simplified function memoization

Kash provides implementations of several caching structures as well as a handy macros for defining memoized functions.

Memoized functions defined using #[kash]/#[io_kash]/kash! macros are thread-safe with the backing function-cache wrapped in a mutex/rwlock, or externally synchronized in the case of #[io_kash].

By default, the cache is not locked for the duration of the function's execution. So initial concurrent calls (on an empty cache) of long-running functions with the same arguments will each execute fully, and each overwrites the memoized value as they complete. To synchronize the execution and caching of not-yet-cached arguments, specify #[kash(sync_writes)] (not supported by #[io_kash]).

• See proc_macro for more procedural macro examples.
• See macros for more declarative macro examples.

Features

• default: Include proc_macro and ahash features
• proc_macro: Include proc macros
• ahash: Enable the optional ahash hasher as default hashing algorithm.
• async: Include support for async functions and async cache stores
• redis_store: Include Redis cache store
• redis_async_std: Include async Redis support using async-std and async-std tls support, implies redis_store and async
• redis_tokio: Include async Redis support using tokio and tokio tls support, implies redis_store and async
• redis_connection_manager: Enable the optional connection-manager feature of redis. Any async redis caches created will use a connection manager instead of a MultiplexedConnection
• redis_ahash: Enable the optional ahash feature of redis
• disk_store: Include disk cache store

The procedural macros (#[kash], #[io_kash]) offer more features, including async support. See the proc_macro and macros modules for more samples, and the examples directory for runnable snippets.

The basic usage looks like:

use kash::kash;

/// Defines a function named `fib` that uses a cache implicitly named `FIB`.
/// By default, the cache will be the function's name in all caps.
/// The following line is equivalent to #[kash(name = "FIB", unbound)]
#[kash]
fn fib(n: u64) -> u64 {
    if n == 0 || n == 1 { return n }
    fib(n-1) + fib(n-2)
}

use std::thread::sleep;
use std::time::Duration;
use kash::kash;

/// Use an explicit cache-type with a custom creation block and custom cache-key generating block
#[kash(
    key = "String",
    size = "100",
    convert = r#"{ format!("{}{}", a, b) }"#
)]
fn keyed(a: &str, b: &str) -> usize {
    let size = a.len() + b.len();
    sleep(Duration::new(size as u64, 0));
    size
}

use kash::io_kash;
use kash::AsyncRedisCache;
use thiserror::Error;

#[derive(Error, Debug, PartialEq, Clone)]
enum ExampleError {
    #[error("error with redis cache `{0}`")]
    RedisError(String),
}

/// Cache the results of an async function in redis. Cache
/// keys will be prefixed with `cache_redis_prefix`.
/// A `map_error` closure must be specified to convert any
/// redis cache errors into the same type of error returned
/// by your function. All `io_kash` functions must return `Result`s.
#[io_kash(
    map_error = r##"|e| ExampleError::RedisError(format!("{:?}", e))"##,
    redis,
)]
async fn async_kash_sleep_secs(secs: u64) -> Result<String, ExampleError> {
    std::thread::sleep(std::time::Duration::from_secs(secs));
    Ok(secs.to_string())
}

use kash::io_kash;
use kash::DiskCache;
use thiserror::Error;

#[derive(Error, Debug, PartialEq, Clone)]
enum ExampleError {
    #[error("error with disk cache `{0}`")]
    DiskError(String),
}

/// Cache the results of a function on disk.
/// Cache files will be stored under the system cache dir
/// unless otherwise specified with `disk_dir` or the `create` argument.
/// A `map_error` closure must be specified to convert any
/// disk cache errors into the same type of error returned
/// by your function. All `io_kash` functions must return `Result`s.
#[io_kash(
    map_error = r##"|e| ExampleError::DiskError(format!("{:?}", e))"##,
    disk
)]
fn kash_sleep_secs(secs: u64) -> Result<String, ExampleError> {
    std::thread::sleep(std::time::Duration::from_secs(secs));
    Ok(secs.to_string())
}

Functions defined via macros will have their results kash using the function's arguments as a key, a convert expression specified on a procedural macros, or a Key block specified on a kash_key! declarative macro.

When a macro-defined function is called, the function's cache is first checked for an already computed (and still valid) value before evaluating the function body.

Due to the requirements of storing arguments and return values in a global cache:

• Function return types:
  • For all store types, except Redis, must be owned and implement Clone
  • For the Redis store type, must be owned and implement serde::Serialize + serde::DeserializeOwned
• Function arguments:
  • For all store types, except Redis, must either be owned and implement Hash + Eq + Clone, the kash_key! macro is used with a Key block specifying key construction, or a convert expression is specified on a procedural macro to specify how to construct a key of a Hash + Eq + Clone type.
  • For the Redis store type, must either be owned and implement Display, or the kash_key! & Key or procedural macro & convert expression used to specify how to construct a key of a Display type.
• Arguments and return values will be cloned in the process of insertion and retrieval. Except for Redis where arguments are formatted into Strings and values are de/serialized.
• Macro-defined functions should not be used to produce side-effectual results!

Thanks

This project is a clone of the awesome https://github.com/jaemk/cached repository

License: MIT