Can now prevent loading of the database if too much data is corrupt

lib/datastore.js

@@ -19,6 +19,7 @@ var customUtils = require('./customUtils')
  * @param {Boolean} options.autoload Optional, defaults to false
  * @param {Function} options.onload Optional, if autoload is used this will be called after the load database with the error object as parameter. If you don't pass it the error will be thrown
  * @param {Function} options.afterSerialization and options.beforeDeserialization Optional, serialization hooks
+ * @param {Number} options.corruptAlertThreshold Optional, threshold after which an alert is thrown if too much data is corrupt
  */
 function Datastore (options) {
   var filename;
@@ -46,6 +47,7 @@ function Datastore (options) {
   this.persistence = new Persistence({ db: this, nodeWebkitAppName: options.nodeWebkitAppName
                                       , afterSerialization: options.afterSerialization
                                       , beforeDeserialization: options.beforeDeserialization
+                                      , corruptAlertThreshold: options.corruptAlertThreshold
                                       });
 
   // This new executor is ready if we don't use persistence

lib/persistence.js

@@ -26,6 +26,7 @@ function Persistence (options) {
   this.db = options.db;
   this.inMemoryOnly = this.db.inMemoryOnly;
   this.filename = this.db.filename;
+  this.corruptAlertThreshold = options.corruptAlertThreshold !== undefined ? options.corruptAlertThreshold : 0.1;
   
   if (!this.inMemoryOnly && this.filename) {
     if (this.filename.charAt(this.filename.length - 1) === '~') {
@@ -241,6 +242,7 @@ Persistence.prototype.treatRawData = function (rawData) {
     , tdata = []
     , i
     , indexes = {}
+    , corruptItems = -1   // Last line of every data file is usually blank so not really corrupt
     ;
     
   for (i = 0; i < data.length; i += 1) {
@@ -260,9 +262,15 @@ Persistence.prototype.treatRawData = function (rawData) {
         delete indexes[doc.$$indexRemoved];
       }
     } catch (e) {
+      corruptItems += 1;
     }
   }
     
+  // A bit lenient on corruption
+  if (data.length > 0 && corruptItems / data.length > this.corruptAlertThreshold) {
+    throw "More than 10% of the data file is corrupt, the wrong beforeDeserialization hook may be used. Cautiously refusing to start NeDB to prevent dataloss"
+  }
+
   Object.keys(dataById).forEach(function (k) {
     tdata.push(dataById[k]);
   });
@@ -320,9 +328,13 @@ Persistence.prototype.loadDatabase = function (cb) {
       Persistence.ensureDirectoryExists(path.dirname(self.filename), function (err) {
         self.ensureDatafileIntegrity(function (exists) {
           storage.readFile(self.filename, 'utf8', function (err, rawData) {
-
             if (err) { return cb(err); }
+            
+            try {
               var treatedData = self.treatRawData(rawData);
+            } catch (e) {
+              return cb(e);
+            }
             
             // Recreate all indexes in the datafile
             Object.keys(treatedData.indexes).forEach(function (key) {

test/persistence.test.js

@@ -268,7 +268,38 @@ describe('Persistence', function () {
     });
   });
 
-  describe.only('Data can be persisted using serialization hooks', function () {
+  it("When treating raw data, refuse to proceed if too much data is corrupt, to avoid data loss", function (done) {
+    var corruptTestFilename = 'workspace/corruptTest.db'
+      , fakeData = '{"_id":"one","hello":"world"}\n' + 'Some corrupt data\n' + '{"_id":"two","hello":"earth"}\n' + '{"_id":"three","hello":"you"}\n'
+      , d
+      ;
+    fs.writeFileSync(corruptTestFilename, fakeData, "utf8");
+
+    // Default corruptAlertThreshold
+    d = new Datastore({ filename: corruptTestFilename });
+    d.loadDatabase(function (err) {
+      assert.isDefined(err);
+      assert.isNotNull(err);
+
+      fs.writeFileSync(corruptTestFilename, fakeData, "utf8");
+      d = new Datastore({ filename: corruptTestFilename, corruptAlertThreshold: 1 });
+      d.loadDatabase(function (err) {
+        assert.isNull(err);
+      
+        fs.writeFileSync(corruptTestFilename, fakeData, "utf8");
+        d = new Datastore({ filename: corruptTestFilename, corruptAlertThreshold: 0 });
+        d.loadDatabase(function (err) {
+          assert.isDefined(err);
+          assert.isNotNull(err);
+
+          done();
+        });
+      });
+    });    
+  });
+  
+  
+  describe('Serialization hooks', function () {
     var as = function (s) { return "before_" + s + "_after"; }
       , bd = function (s) { return s.substring(7, s.length - 6); } 
   
@@ -316,7 +347,6 @@ describe('Persistence', function () {
 
         done();
       });
-    
     });
     
     it("A serialization hook can be used to transform data before writing new state to disk", function (done) {
@@ -507,7 +537,7 @@ describe('Persistence', function () {
       });
     });
     
-  });
+  });   // ==== End of 'Serialization hooks' ==== //
   
   describe('Prevent dataloss when persisting data', function () {