save tip as part of block db operations

lib/services/db.js

@@ -62,7 +62,8 @@ util.inherits(DB, Service);
 DB.dependencies = ['bitcoind'];
 
 DB.PREFIXES = {
-  BLOCKS: new Buffer('01', 'hex')
+  BLOCKS: new Buffer('01', 'hex'),
+  TIP: new Buffer('04', 'hex')
 };
 
 /**
@@ -109,45 +110,14 @@ DB.prototype.start = function(callback) {
     });
   });
 
-  // Does our database already have a tip?
-  self.getMetadata(function(err, metadata) {
+  self.loadTip(function(err) {
     if(err) {
       return callback(err);
-    } else if(!metadata || !metadata.tip) {
-      self.tip = self.genesis;
-      self.tip.__height = 0;
-      self.connectBlock(self.genesis, function(err) {
-        if(err) {
-          return callback(err);
-        }
-
-        self.emit('addblock', self.genesis);
-        self.saveMetadata();
-        self.sync();
-        self.emit('ready');
-        setImmediate(callback);
-
-      });
-    } else {
-      self.getBlock(metadata.tip, function(err, tip) {
-        if(err) {
-          log.warn(
-            'Database is in an inconsistent state, a reindex is needed. Could not get current tip:',
-            metadata.tip
-          );
-          return callback(err);
-        }
-        self.tip = tip;
-        var blockIndex = self.node.services.bitcoind.getBlockIndex(self.tip.hash);
-        if (!blockIndex) {
-          return callback(new Error('Could not get height for tip.'));
-        }
-        self.tip.__height = blockIndex.height;
-        self.sync();
-        self.emit('ready');
-        setImmediate(callback);
-      });
     }
+
+    self.sync();
+    self.emit('ready');
+    setImmediate(callback);
   });
 };
 
@@ -220,6 +190,52 @@ DB.prototype.getAPIMethods = function() {
   return methods;
 };
 
+DB.prototype.loadTip = function(callback) {
+  var self = this;
+
+  var options = {
+    keyEncoding: 'binary',
+    valueEncoding: 'binary'
+  };
+
+  self.store.get(DB.PREFIXES.TIP, options, function(err, tipData) {
+    if(err && err instanceof levelup.errors.NotFoundError) {
+      self.tip = self.genesis;
+      self.tip.__height = 0;
+      self.connectBlock(self.genesis, function(err) {
+        if(err) {
+          return callback(err);
+        }
+
+        self.emit('addblock', self.genesis);
+        callback();
+      });
+      return;
+    } else if(err) {
+      return callback(err);
+    }
+
+    var hash = tipData.toString('hex');
+
+    self.getBlock(hash, function(err, tip) {
+      if(err) {
+        log.warn('Database is in an inconsistent state, a reindex is needed. Could not get current tip:',
+          hash
+        );
+        return callback(err);
+      }
+
+      self.tip = tip;
+      var blockIndex = self.node.services.bitcoind.getBlockIndex(self.tip.hash);
+      if(!blockIndex) {
+        return callback(new Error('Could not get height for tip.'));
+      }
+      self.tip.__height = blockIndex.height;
+      callback();
+    });
+  });
+};
+
 /**
  * Will get a block from bitcoind and give a Bitcore Block
  * @param {String|Number} hash - A block hash or block height
@@ -404,54 +420,6 @@ DB.prototype.getPrevHash = function(blockHash, callback) {
   });
 };
 
-/**
- * Saves metadata to the database
- * @param {Function} callback - A function that accepts: Error
- */
-DB.prototype.saveMetadata = function(callback) {
-  var self = this;
-
-  function defaultCallback(err) {
-    if (err) {
-      self.emit('error', err);
-    }
-  }
-
-  callback = callback || defaultCallback;
-
-  var metadata = {
-    tip: self.tip ? self.tip.hash : null
-  };
-
-  this.store.put('metadata', JSON.stringify(metadata), {}, callback);
-
-};
-
-/**
- * Retrieves metadata from the database
- * @param {Function} callback - A function that accepts: Error and Object
- */
-DB.prototype.getMetadata = function(callback) {
-  var self = this;
-
-  self.store.get('metadata', {}, function(err, data) {
-    if (err instanceof levelup.errors.NotFoundError) {
-      return callback(null, {});
-    } else if (err) {
-      return callback(err);
-    }
-
-    var metadata;
-    try {
-      metadata = JSON.parse(data);
-    } catch(e) {
-      return callback(new Error('Could not parse metadata'));
-    }
-
-    callback(null, metadata);
-  });
-};
-
 /**
  * Connects a block to the database and add indexes
  * @param {Block} block - The bitcore block
@@ -506,6 +474,14 @@ DB.prototype.runAllBlockHandlers = function(block, add, callback) {
     this.subscriptions.block[i].emit('db/block', block.hash);
   }
 
+  // Update tip
+  var tipHash = add ? new Buffer(block.hash, 'hex') : BufferUtil.reverse(block.header.prevHash);
+  operations.push({
+    type: 'put',
+    key: DB.PREFIXES.TIP,
+    value: tipHash
+  });
+
   // Update block index
   operations.push({
     type: add ? 'put' : 'del',
@@ -668,7 +644,6 @@ DB.prototype.syncRewind = function(block, done) {
             // Set the new tip
             previousTip.__height = self.tip.__height - 1;
             self.tip = previousTip;
-            self.saveMetadata();
             self.emit('removeblock', tip);
             removeDone();
           });
@@ -725,8 +700,6 @@ DB.prototype.sync = function() {
             return done(err);
           }
           self.tip = block;
-          log.debug('Saving metadata');
-          self.saveMetadata();
           log.debug('Chain added block to main chain');
           self.emit('addblock', block);
           setImmediate(done);