Loading Cache Wrapper ¶

The library adds a thin layer on top of lru\expirable cache.

Main features:

• LoadingCache (guava style)
• Limit maximum cache size (in bytes)
• Limit maximum key size
• Limit maximum size of a value
• Limit number of keys
• TTL support (ExpirableCache and RedisCache)
• Callback on eviction event (not supported in RedisCache)
• Functional style invalidation
• Functional options
• Sane defaults

Install and update¶

go get -u github.com/go-pkgz/lcw/v2

Usage¶

package main

import (
    "github.com/go-pkgz/lcw/v2"
)

func main() {
    o := lcw.NewOpts[int]()
    cache, err := lcw.NewLruCache(o.MaxKeys(500), o.MaxCacheSize(65536), o.MaxValSize(200), o.MaxKeySize(32))
    if err != nil {
        panic("failed to create cache")
    }
    defer cache.Close()

    val, err := cache.Get("key123", func() (int, error) {
        res, err := getDataFromSomeSource(params) // returns int
        return res, err
    })

    if err != nil {
        panic("failed to get data")
    }

    s := val // cached value
}

Cache with URI¶

Cache can be created with URIs:

• mem://lru?max_key_size=10&max_val_size=1024&max_keys=50&max_cache_size=64000 - creates LRU cache with given limits
• mem://expirable?ttl=30s&max_key_size=10&max_val_size=1024&max_keys=50&max_cache_size=64000 - create expirable cache
• redis://10.0.0.1:1234?db=16&password=qwerty&network=tcp4&dial_timeout=1s&read_timeout=5s&write_timeout=3s - create redis cache
• nop:// - create Nop cache

Scoped cache¶

Scache provides a wrapper on top of all implementations of LoadingCache with a number of special features:

1. Key is not a string, but a composed type made from partition, key-id and list of scopes (tags).
2. Value type limited to []byte
3. Added Flush method for scoped/tagged invalidation of multiple records in a given partition
4. A simplified interface with Get, Stat, Flush and Close only.

Details¶

• In all cache types other than Redis (e.g. LRU and Expirable at the moment) values are stored as-is which means that mutable values can be changed outside of cache. ExampleLoadingCache_Mutability illustrates that.
• All byte-size limits (MaxCacheSize and MaxValSize) only work for values implementing lcw.Sizer interface.
• Negative limits (max options) rejected
• The implementation started as a part of remark42 and later on moved to go-pkgz/rest library and finally generalized to become lcw.