Client Side Caching (#2947)

* CSC POC ontop of Parser

* add csc file that weren't merged after patch

* address review comments

* nits to try and fix github

* last change from review

* Update client-side cache and improve documentation

* Add client side caching RESP3 validation

* Add documentation for RESP and unstableResp3 options

* Add comprehensive cache statistics

The `CacheStats` class provides detailed metrics like hit/miss counts,
load success/failure counts, total load time, and eviction counts.
It also offers derived metrics such as hit/miss rates, load failure rate,
and average load penalty. The design is inspired by Caffeine.

`BasicClientSideCache` now uses a `StatsCounter` to accumulate these
statistics, exposed via a new `stats()` method. The previous
`cacheHits()` and `cacheMisses()` methods have been removed.

A `recordStats` option (default: true) in `ClientSideCacheConfig`
allows disabling statistics collection.

---------

Co-authored-by: Shaya Potter <shaya@redislabs.com>

packages/client/lib/cluster/cluster-slots.spec.ts

@@ -0,0 +1,48 @@
+import { strict as assert } from 'node:assert';
+import { EventEmitter } from 'node:events';
+import { RedisClusterOptions, RedisClusterClientOptions } from './index';
+import RedisClusterSlots from './cluster-slots';
+
+describe('RedisClusterSlots', () => {
+  describe('initialization', () => {
+
+    describe('clientSideCache validation', () => {
+      const mockEmit = ((_event: string | symbol, ..._args: any[]): boolean => true) as EventEmitter['emit'];
+      const clientSideCacheConfig = { ttl: 0, maxEntries: 0 };
+      const rootNodes: Array<RedisClusterClientOptions> = [
+        { socket: { host: 'localhost', port: 30001 } }
+      ];
+
+      it('should throw error when clientSideCache is enabled with RESP 2', () => {
+        assert.throws(
+          () => new RedisClusterSlots({
+            rootNodes,
+            clientSideCache: clientSideCacheConfig,
+            RESP: 2 as const,
+          }, mockEmit),
+          new Error('Client Side Caching is only supported with RESP3')
+        );
+      });
+
+      it('should throw error when clientSideCache is enabled with RESP undefined', () => {
+        assert.throws(
+          () => new RedisClusterSlots({
+            rootNodes,
+            clientSideCache: clientSideCacheConfig,
+          }, mockEmit),
+          new Error('Client Side Caching is only supported with RESP3')
+        );
+      });
+
+      it('should not throw when clientSideCache is enabled with RESP 3', () => {
+        assert.doesNotThrow(() =>
+          new RedisClusterSlots({
+            rootNodes,
+            clientSideCache: clientSideCacheConfig,
+            RESP: 3 as const,
+          }, mockEmit)
+        );
+      });
+    });
+  });
+});