keep cached RBF info for 24 hours after tx leaves the mempool

backend/src/api/rbf-cache.ts

@@ -1,46 +1,29 @@
 import { TransactionExtended } from "../mempool.interfaces";
 
-export interface CachedRbf {
-  txid: string;
-  expires: Date;
-}
-
-export interface CachedRbfs {
-  txids: string[];
-  expires: Date;
-}
-
 class RbfCache {
-  private replacedby: { [txid: string]: CachedRbf; } = {};
-  private replaces: { [txid: string]: CachedRbfs } = {};
+  private replacedBy: { [txid: string]: string; } = {};
+  private replaces: { [txid: string]: string[] } = {};
   private txs: { [txid: string]: TransactionExtended } = {};
+  private expiring: { [txid: string]: Date } = {};
 
   constructor() {
     setInterval(this.cleanup.bind(this), 1000 * 60 * 60);
   }
 
   public add(replacedTx: TransactionExtended, newTxId: string): void {
-    const expiry = new Date(Date.now() + 1000 * 604800); // 1 week
-    this.replacedby[replacedTx.txid] = {
-      expires: expiry,
-      txid: newTxId,
-    };
+    this.replacedBy[replacedTx.txid] = newTxId;
     this.txs[replacedTx.txid] = replacedTx;
     if (!this.replaces[newTxId]) {
-      this.replaces[newTxId] = {
-        txids: [],
-        expires: expiry,
-      };
+      this.replaces[newTxId] = [];
     }
-    this.replaces[newTxId].txids.push(replacedTx.txid);
-    this.replaces[newTxId].expires = expiry;
+    this.replaces[newTxId].push(replacedTx.txid);
   }
 
-  public getReplacedBy(txId: string): CachedRbf | undefined {
-    return this.replacedby[txId];
+  public getReplacedBy(txId: string): string | undefined {
+    return this.replacedBy[txId];
   }
 
-  public getReplaces(txId: string): CachedRbfs | undefined {
+  public getReplaces(txId: string): string[] | undefined {
     return this.replaces[txId];
   }
 
@@ -48,17 +31,32 @@ class RbfCache {
     return this.txs[txId];
   }
 
+  // flag a transaction as removed from the mempool
+  public evict(txid): void {
+    this.expiring[txid] = new Date(Date.now() + 1000 * 86400); // 24 hours
+  }
+
   private cleanup(): void {
     const currentDate = new Date();
-    for (const c in this.replacedby) {
-      if (this.replacedby[c].expires < currentDate) {
-        delete this.replacedby[c];
-        delete this.txs[c];
+    for (const txid in this.expiring) {
+      if (this.expiring[txid] < currentDate) {
+        delete this.expiring[txid];
+        this.remove(txid);
       }
     }
-    for (const c in this.replaces) {
-      if (this.replaces[c].expires < currentDate) {
-        delete this.replaces[c];
+  }
+
+  // remove a transaction & all previous versions from the cache
+  private remove(txid): void {
+    // don't remove a transaction while a newer version remains in the mempool
+    if (this.replaces[txid] && !this.replacedBy[txid]) {
+      const replaces = this.replaces[txid];
+      delete this.replaces[txid];
+      for (const tx of replaces) {
+        // recursively remove prior versions from the cache
+        delete this.replacedBy[tx];
+        delete this.txs[tx];
+        this.remove(tx);
       }
     }
   }