ConcurrentLru Quickstart

ConcurrentLru is a thread-safe bounded size pseudo LRU. This page describes how to use the ConcurrentLru, and how it is implemented.

Quickstart

ConcurrentLru is intended to be a drop in replacement for ConcurrentDictionary, but with the benefit of bounded size based on an LRU eviction policy.

The code samples below illustrate how to create an LRU then get/remove/update items:

Constructor

int capacity = 666;
var lru = new ConcurrentLru<int, SomeItem>(capacity);

Getting Items

bool success1 = lru.TryGet(1, out var value);
var value1 = lru.GetOrAdd(1, (k) => new SomeItem(k));
var value2 = await lru.GetOrAddAsync(0, (k) => Task.FromResult(new SomeItem(k)));

Removing Items

bool success2 = lru.TryRemove(1); // remove item with key == 1
lru.Clear();
lru.Eviction.Policy.Value.Trim(1); // remove the coldest item

Updating Items

var item = new SomeItem(1);
bool success3 = lru.TryUpdate(1, item);
lru.AddOrUpdate(1, item);

Diagnostics

Console.WriteLine(lru.Metrics.Value.HitRatio);

// enumerate keys
foreach (var k in lru.Keys)
{
   Console.WriteLine(k);
}

// enumerate key value pairs
foreach (var kvp in lru)
{
   Console.WriteLine($"{kvp.Key} {kvp.Value}");
}

// register event on item removed
lru.Events.Value.ItemRemoved += (source, args) => Console.WriteLine($"{args.Reason} {args.Key} {args.Value}");