Don't wait for 100% mempool sync before starting block indexing

backend/src/api/mempool.ts

@@ -13,6 +13,7 @@ class Mempool {
   private static WEBSOCKET_REFRESH_RATE_MS = 10000;
   private static LAZY_DELETE_AFTER_SECONDS = 30;
   private inSync: boolean = false;
+  private mempoolCacheDelta: number = -1;
   private mempoolCache: { [txId: string]: TransactionExtended } = {};
   private mempoolInfo: IBitcoinApi.MempoolInfo = { loaded: false, size: 0, bytes: 0, usage: 0, total_fee: 0,
                                                     maxmempool: 300000000, mempoolminfee: 0.00001000, minrelaytxfee: 0.00001000 };
@@ -32,6 +33,17 @@ class Mempool {
     setInterval(this.deleteExpiredTransactions.bind(this), 20000);
   }
 
+  /**
+   * Return true if we should leave resources available for mempool tx caching
+   */
+  public hasPriority(): boolean {
+    if (this.inSync) {
+      return false;
+    } else {
+      return this.mempoolCacheDelta == -1 || this.mempoolCacheDelta > 25;
+    }
+  }
+
   public isInSync(): boolean {
     return this.inSync;
   }
@@ -100,6 +112,8 @@ class Mempool {
     const diff = transactions.length - currentMempoolSize;
     const newTransactions: TransactionExtended[] = [];
 
+    this.mempoolCacheDelta = Math.abs(diff);
+
     if (!this.inSync) {
       loadingIndicators.setProgress('mempool', Object.keys(this.mempoolCache).length / transactions.length * 100);
     }
@@ -174,6 +188,8 @@ class Mempool {
       loadingIndicators.setProgress('mempool', 100);
     }
 
+    this.mempoolCacheDelta = Math.abs(transactions.length - Object.keys(this.mempoolCache).length);
+
     if (this.mempoolChangedCallback && (hasChange || deletedTransactions.length)) {
       this.mempoolChangedCallback(this.mempoolCache, newTransactions, deletedTransactions);
     }