Write cache.json on startup if it doesn't exist.

Write mempool and block data to cache on every new block
fixes #146

backend/src/api/blocks.ts

@@ -3,6 +3,7 @@ import logger from '../logger';
 import memPool from './mempool';
 import { Block, TransactionExtended, TransactionMinerInfo } from '../interfaces';
 import { Common } from './common';
+import diskCache from './disk-cache';
 
 class Blocks {
   private static INITIAL_BLOCK_AMOUNT = 8;
@@ -99,6 +100,7 @@ class Blocks {
       if (this.newBlockCallbacks.length) {
         this.newBlockCallbacks.forEach((cb) => cb(block, txIds, transactions));
       }
+      diskCache.$saveCacheToDiskAsync();
     }
   }
 

backend/src/api/disk-cache.ts

@@ -6,10 +6,16 @@ import blocks from './blocks';
 import logger from '../logger';
 
 class DiskCache {
-  static FILE_NAME = './cache.json';
+  private static FILE_NAME = './cache.json';
+  private enabled = true;
 
   constructor() {
     if (process.env.workerId === '0' || !config.MEMPOOL.SPAWN_CLUSTER_PROCS) {
+      if (!fs.existsSync(DiskCache.FILE_NAME)) {
+        fs.closeSync(fs.openSync(DiskCache.FILE_NAME, 'w'));
+        logger.info('Disk cache file created');
+      }
+
       process.on('SIGINT', () => {
         this.saveCacheToDisk();
         process.exit(2);
@@ -19,19 +25,28 @@ class DiskCache {
         this.saveCacheToDisk();
         process.exit(2);
       });
+    } else {
+      this.enabled = false;
     }
   }
 
-  saveCacheToDisk() {
-    this.saveData(JSON.stringify({
-      mempool: memPool.getMempool(),
-      blocks: blocks.getBlocks(),
-    }));
-    logger.info('Mempool and blocks data saved to disk cache');
+  async $saveCacheToDiskAsync(): Promise<void> {
+    if (!this.enabled) {
+      return;
+    }
+    try {
+      await this.$saveDataAsync(JSON.stringify({
+        mempool: memPool.getMempool(),
+        blocks: blocks.getBlocks(),
+      }));
+      logger.info('Mempool and blocks data saved to disk cache');
+    } catch (e) {
+      logger.warn('Error writing to cache file asynchronously');
+    }
   }
 
   loadMempoolCache() {
-    const cacheData = this.loadData();
+    const cacheData = this.loadDataSync();
     if (cacheData) {
       logger.info('Restoring mempool and blocks data from disk cache');
       const data = JSON.parse(cacheData);
@@ -40,11 +55,30 @@ class DiskCache {
     }
   }
 
-  private saveData(dataBlob: string) {
+  private saveCacheToDisk() {
+    this.saveDataSync(JSON.stringify({
+      mempool: memPool.getMempool(),
+      blocks: blocks.getBlocks(),
+    }));
+    logger.info('Mempool and blocks data saved to disk cache');
+  }
+
+  private $saveDataAsync(dataBlob: string): Promise<void> {
+    return new Promise((resolve, reject) => {
+      fs.writeFile(DiskCache.FILE_NAME, dataBlob, (err) => {
+        if (err) {
+          return reject(err);
+        }
+        resolve();
+      });
+    });
+  }
+
+  private saveDataSync(dataBlob: string) {
     fs.writeFileSync(DiskCache.FILE_NAME, dataBlob, 'utf8');
   }
 
-  private loadData(): string {
+  private loadDataSync(): string {
     return fs.readFileSync(DiskCache.FILE_NAME, 'utf8');
   }
 }