From abce780033d2f1dbfc7c75196bd059454c36ce8f Mon Sep 17 00:00:00 2001
From: filvecchiato <filippo@parity.io>
Date: Thu, 31 Oct 2024 13:59:27 +0100
Subject: [PATCH] fix: update LRUcache to not keep thread (#6013)

---
 packages/rpc-core/src/bundle.ts       |  2 -
 packages/rpc-provider/src/lru.spec.ts | 19 +++++--
 packages/rpc-provider/src/lru.ts      | 82 ++++++++++-----------------
 3 files changed, 45 insertions(+), 58 deletions(-)

diff --git a/packages/rpc-core/src/bundle.ts b/packages/rpc-core/src/bundle.ts
index 6c86702666f..702f22b43a6 100644
--- a/packages/rpc-core/src/bundle.ts
+++ b/packages/rpc-core/src/bundle.ts
@@ -146,8 +146,6 @@ export class RpcCore {
    * @description Manually disconnect from the attached provider
    */
   public async disconnect (): Promise<void> {
-    await this.#storageCache.clearInterval();
-
     return this.provider.disconnect();
   }
 
diff --git a/packages/rpc-provider/src/lru.spec.ts b/packages/rpc-provider/src/lru.spec.ts
index d36e05b677c..43169ed7012 100644
--- a/packages/rpc-provider/src/lru.spec.ts
+++ b/packages/rpc-provider/src/lru.spec.ts
@@ -9,11 +9,7 @@ describe('LRUCache', (): void => {
   let lru: LRUCache | undefined;
 
   beforeEach((): void => {
-    lru = new LRUCache(4);
-  });
-  afterEach(async () => {
-    await lru?.clearInterval();
-    lru = undefined;
+    lru = new LRUCache(4, 500);
   });
 
   it('allows getting of items below capacity', (): void => {
@@ -62,4 +58,17 @@ describe('LRUCache', (): void => {
     expect(lru?.entries()).toEqual([['6', '666'], ['4', '4433'], ['3', '333'], ['5', '555']]);
     expect(lru?.length === lru?.lengthData && lru?.length === lru?.lengthRefs).toBe(true);
   });
+
+  it('evicts items with TTL', (): void => {
+    const keys = ['1', '2', '3', '4', '5'];
+
+    keys.forEach((k) => lru?.set(k, `${k}${k}${k}`));
+
+    expect(lru?.entries()).toEqual([['5', '555'], ['4', '444'], ['3', '333'], ['2', '222']]);
+
+    setTimeout((): void => {
+      lru?.get('3');
+      expect(lru?.entries()).toEqual([['3', '333']]);
+    }, 800);
+  });
 });
diff --git a/packages/rpc-provider/src/lru.ts b/packages/rpc-provider/src/lru.ts
index 2a5cc3cdbf4..0a6927ef1d7 100644
--- a/packages/rpc-provider/src/lru.ts
+++ b/packages/rpc-provider/src/lru.ts
@@ -9,25 +9,27 @@ export const DEFAULT_CAPACITY = 64;
 
 class LRUNode {
   readonly key: string;
-  #lastAccess: number;
+  #expires: number;
+  #ttl: number;
   readonly createdAt: number;
 
   public next: LRUNode;
   public prev: LRUNode;
 
-  constructor (key: string) {
+  constructor (key: string, ttl: number) {
     this.key = key;
-    this.#lastAccess = Date.now();
-    this.createdAt = this.#lastAccess;
+    this.#ttl = ttl;
+    this.#expires = Date.now() + ttl;
+    this.createdAt = Date.now();
     this.next = this.prev = this;
   }
 
   public refresh (): void {
-    this.#lastAccess = Date.now();
+    this.#expires = Date.now() + this.#ttl;
   }
 
-  public get lastAccess (): number {
-    return this.#lastAccess;
+  public get expiry (): number {
+    return this.#expires;
   }
 }
 
@@ -43,29 +45,17 @@ export class LRUCache {
   #tail: LRUNode;
 
   readonly #ttl: number;
-  readonly #ttlInterval: number;
-  #ttlTimerId: ReturnType<typeof setInterval> | null = null;
 
-  constructor (capacity = DEFAULT_CAPACITY, ttl = 30000, ttlInterval = 15000) {
+  constructor (capacity = DEFAULT_CAPACITY, ttl = 30000) {
     this.capacity = capacity;
     this.#ttl = ttl;
-    this.#ttlInterval = ttlInterval;
-    this.#head = this.#tail = new LRUNode('<empty>');
-
-    // make sure the interval is not longer than the ttl
-    if (this.#ttlInterval > this.#ttl) {
-      this.#ttlInterval = this.#ttl;
-    }
+    this.#head = this.#tail = new LRUNode('<empty>', ttl);
   }
 
   get ttl (): number {
     return this.#ttl;
   }
 
-  get ttlInterval (): number {
-    return this.#ttlInterval;
-  }
-
   get length (): number {
     return this.#length;
   }
@@ -115,9 +105,14 @@ export class LRUCache {
     if (data) {
       this.#toHead(key);
 
+      // Evict TTL once data is refreshed
+      this.#evictTTL();
+
       return data as T;
     }
 
+    this.#evictTTL();
+
     return null;
   }
 
@@ -125,7 +120,7 @@ export class LRUCache {
     if (this.#data.has(key)) {
       this.#toHead(key);
     } else {
-      const node = new LRUNode(key);
+      const node = new LRUNode(key, this.#ttl);
 
       this.#refs.set(node.key, node);
 
@@ -148,32 +143,25 @@ export class LRUCache {
       }
     }
 
-    if (this.#ttl > 0 && !this.#ttlTimerId) {
-      this.#ttlTimerId = setInterval(() => {
-        this.#ttlClean();
-      }, this.#ttlInterval);
-    }
+    // Evict TTL once data is refreshed or added
+    this.#evictTTL();
 
     this.#data.set(key, value);
   }
 
-  #ttlClean () {
+  #evictTTL () {
   // Find last node to keep
-    const expires = Date.now() - this.#ttl;
-
-    // traverse map to find the lastAccessed
-    while (this.#tail.lastAccess && this.#tail.lastAccess < expires && this.#length > 0) {
-      if (this.#ttlTimerId && this.#length === 0) {
-        clearInterval(this.#ttlTimerId);
-        this.#ttlTimerId = null;
-        this.#head = this.#tail = new LRUNode('<empty>');
-      } else {
-        this.#refs.delete(this.#tail.key);
-        this.#data.delete(this.#tail.key);
-        this.#length -= 1;
-        this.#tail = this.#tail.prev;
-        this.#tail.next = this.#head;
-      }
+    // traverse map to find the expired nodes
+    while (this.#tail.expiry && this.#tail.expiry < Date.now() && this.#length > 0) {
+      this.#refs.delete(this.#tail.key);
+      this.#data.delete(this.#tail.key);
+      this.#length -= 1;
+      this.#tail = this.#tail.prev;
+      this.#tail.next = this.#head;
+    }
+
+    if (this.#length === 0) {
+      this.#head = this.#tail = new LRUNode('<empty>', this.#ttl);
     }
   }
 
@@ -190,12 +178,4 @@ export class LRUCache {
       this.#head = ref;
     }
   }
-
-  // eslint-disable-next-line @typescript-eslint/require-await
-  public async clearInterval (): Promise<void> {
-    if (this.#ttlTimerId) {
-      clearInterval(this.#ttlTimerId);
-      this.#ttlTimerId = null;
-    }
-  }
 }