wdb: add median time past.

lib/wallet/walletdb.js

@@ -14,6 +14,7 @@ const {BloomFilter} = require('@handshake-org/bfilter');
 const {Lock, MapLock} = require('bmutex');
 const bdb = require('bdb');
 const Logger = require('blgr');
+const LRU = require('blru');
 const {safeEqual} = require('bcrypto/lib/safe');
 const aes = require('bcrypto/lib/aes');
 const Network = require('../protocol/network');
@@ -71,6 +72,9 @@ class WalletDB extends EventEmitter {
     this.state = new ChainState();
     this.height = 0;
 
+    // block time cache by height.
+    this.timeCache = new LRU(30);
+
     // wallets
     this.primary = null;
     this.wallets = new Map();
@@ -340,6 +344,7 @@ class WalletDB extends EventEmitter {
       this.unregister(wallet);
     }
 
+    this.timeCache.reset();
     await this.db.close();
     this.logger.info('WalletDB Closed.');
     this.emit('close');
@@ -2247,6 +2252,83 @@ class WalletDB extends EventEmitter {
     return block.hash;
   }
 
+  /**
+   * Get block time.
+   * @param {Number} height
+   * @returns {Promise<Number?>}
+   */
+
+  async getBlockTime(height) {
+    assert(typeof height === 'number');
+
+    if (height < 0)
+      return null;
+
+    const cache = this.timeCache.get(height);
+
+    if (cache != null)
+      return cache;
+
+    const block = await this.getBlock(height);
+
+    if (!block)
+      return null;
+
+    this.timeCache.set(height, block.time);
+
+    return block.time;
+  }
+
+  /**
+   * Calculate median time past.
+   * @param {Number} height
+   * @returns {Promise<Number>}
+   */
+
+  async getMedianTime(height) {
+    assert(typeof height === 'number');
+    const timespan = consensus.MEDIAN_TIMESPAN;
+    const median = [];
+
+    let time = await this.getBlockTime(height);
+
+    for (let i = 0; i < timespan && time; i++) {
+      median.push(time);
+
+      time = await this.getBlockTime(height - i - 1);
+    }
+
+    median.sort(cmp);
+
+    return median[median.length >>> 1];
+  }
+
+  /**
+   * Median time as if the actively adding block is the tip.
+   * @param {Number} prevHeight
+   * @param {Number} tipTime
+   */
+
+  async getMedianTimeTip(prevHeight, tipTime) {
+    assert(typeof prevHeight === 'number');
+    assert(typeof tipTime === 'number');
+
+    const timespan = consensus.MEDIAN_TIMESPAN;
+    const median = [];
+
+    let time = tipTime;
+
+    for (let i = 0; i < timespan && time; i++) {
+      median.push(time);
+
+      time = await this.getBlockTime(prevHeight - i);
+    }
+
+    median.sort(cmp);
+
+    return median[median.length >>> 1];
+  }
+
   /**
    * Sync with chain height.
    * @param {Number} height
@@ -2290,6 +2372,7 @@ class WalletDB extends EventEmitter {
     let total = 0;
 
     await iter.each(async (key, value) => {
+      this.timeCache.start();
       const [height] = layout.b.decode(key);
       const block = MapRecord.decode(value);
       this.logger.info('Reverting block: %d', height);
@@ -2299,6 +2382,8 @@ class WalletDB extends EventEmitter {
         assert(wallet);
         total += await wallet.revert(height);
       }
+      this.timeCache.unpush(height);
+      this.timeCache.commit();
     });
 
     this.logger.info('Rolled back %d WalletDB transactions.', total);
@@ -2314,8 +2399,15 @@ class WalletDB extends EventEmitter {
   async addBlock(entry, txs) {
     const unlock = await this.txLock.lock();
 
+    this.timeCache.start();
+
     try {
-      return await this._addBlock(entry, txs);
+      const result = await this._addBlock(entry, txs);
+      this.timeCache.commit();
+      return result;
+    } catch (e) {
+      this.timeCache.drop();
+      throw e;
     } finally {
       unlock();
     }
@@ -2355,6 +2447,8 @@ class WalletDB extends EventEmitter {
       return 0;
     }
 
+    this.timeCache.push(tip.height, tip.time);
+
     const walletTxs = [];
 
     try {
@@ -2397,7 +2491,13 @@ class WalletDB extends EventEmitter {
   async removeBlock(entry) {
     const unlock = await this.txLock.lock();
     try {
-      return await this._removeBlock(entry);
+      this.timeCache.start();
+      const result = await this._removeBlock(entry);
+      this.timeCache.commit();
+      return result;
+    } catch (e) {
+      this.timeCache.drop();
+      throw e;
     } finally {
       unlock();
     }
@@ -2429,6 +2529,8 @@ class WalletDB extends EventEmitter {
     const prev = await this.getBlock(tip.height - 1);
     assert(prev);
 
+    this.timeCache.unpush(tip.height);
+
     // Get the map of block->wids.
     const map = await this.getBlockMap(tip.height);
 
@@ -2476,9 +2578,13 @@ class WalletDB extends EventEmitter {
       return;
     }
 
+    this.timeCache.start();
+
     try {
       await this._addBlock(entry, txs);
+      this.timeCache.commit();
     } catch (e) {
+      this.timeCache.drop();
       this.emit('error', e);
       throw e;
     }
@@ -2745,6 +2851,10 @@ function toString(buf) {
   return buf.toString('ascii', 1, buf.length);
 }
 
+function cmp(a, b) {
+  return a - b;
+}
+
 /*
  * Expose
  */

test/wallet-test.js

@@ -2831,9 +2831,14 @@ describe('Wallet', function() {
       await node.close();
     });
 
-    async function mineBlock(tip) {
+    async function createBlock(tip) {
       const job = await miner.createJob(tip);
       const block = await job.mineAsync();
+      return block;
+    }
+
+    async function mineBlock(tip) {
+      const block = await createBlock(tip);
       return chain.add(block);
     }
 
@@ -2941,6 +2946,45 @@ describe('Wallet', function() {
         await wclient.close();
       }
     });
+
+    it('should get same mtp for chain and wallet', async () => {
+      const assertSameMTP = async (mtp) => {
+        assert.strictEqual(wdb.state.height, chain.tip.height);
+
+        const chainMTP = await node.chain.getMedianTime(chain.tip);
+        const walletMTP = await wdb.getMedianTime(wdb.state.height);
+
+        assert.strictEqual(walletMTP, chainMTP);
+        if (mtp)
+          assert.strictEqual(mtp, chainMTP);
+      };
+
+      await assertSameMTP();
+
+      const times = [];
+      const mtp = await node.chain.getMedianTime(chain.tip);
+      times[chain.tip.height] = mtp;
+      for (let i = 0; i < 40; i++) {
+        const block = await createBlock(chain.tip);
+        const futureMTP = await wdb.getMedianTimeTip(chain.tip.height, block.time);
+        await chain.add(block);
+        await assertSameMTP(futureMTP);
+        const mtp = await node.chain.getMedianTime(chain.tip);
+        times[chain.tip.height] = mtp;
+      }
+
+      // revert all
+      for (let i = 0; i < 40; i++) {
+        const entry = chain.tip;
+        const mtp = await chain.getMedianTime(entry);
+        const tipMtp = await wdb.getMedianTimeTip(entry.height - 1, entry.time);
+        await assertSameMTP(times[entry.height]);
+        assert.strictEqual(tipMtp, times[entry.height]);
+        assert.strictEqual(tipMtp, mtp);
+
+        await chain.disconnect(entry);
+      }
+    });
   });
 
   describe('Wallet Name Claims', function() {