Externalized persistence of the cached db and of new state

lib/datastore.js

@@ -7,6 +7,7 @@ var fs = require('fs')
   , Index = require('./indexes')
   , util = require('util')
   , _ = require('underscore')
+  , Persistence = require('./persistence')
   ;
 
 
@@ -46,6 +47,9 @@ function Datastore (options) {
     this.filename = customUtils.getNWAppFilename(options.nodeWebkitAppName, this.filename);
   }
 
+  // Persistence handling
+  this.persistence = new Persistence({ db: this });
+
   // This new executor is ready if we don't use persistence
   // If we do, it will only be ready once loadDatabase is called
   this.executor = new Executor();
@@ -278,7 +282,7 @@ Datastore.prototype._loadDatabase = function (cb) {
             }
 
             self.datafileSize = treatedData.length;
-            self.persistCachedDatabase(cb);
+            self.persistence.persistCachedDatabase(cb);
           });
         });
       });
@@ -330,61 +334,7 @@ Datastore.treatRawData = function (rawData) {
 };
 
 
-/**
- * Persist cached database
- * This serves as a compaction function since the cache always contains only the number of documents in the collection
- * while the data file is append-only so it may grow larger
- * @param {Function} cb Optional callback, signature: err
- */
-Datastore.prototype.persistCachedDatabase = function (cb) {
-  var callback = cb || function () {}
-    , toPersist = ''
-    ;
-
-  this.getAllData().forEach(function (doc) {
-    toPersist += model.serialize(doc) + '\n';
-  });
-
-  if (toPersist.length === 0) { return callback(null); }
 
-  fs.writeFile(this.filename, toPersist, function (err) { return callback(err); });
-};
-
-
-/**
- * Persist new state for the given newDocs (can be insertion, update or removal)
- * Use an append-only format
- * @param {Array} newDocs Can be empty if no doc was updated/removed
- * @param {Function} cb Optional, signature: err
- */
-Datastore.prototype._persistNewState = function (newDocs, cb) {
-  var self = this
-    , toPersist = ''
-    , callback = cb || function () {}
-    ;
-
-  // In-memory only datastore
-  if (self.inMemoryOnly) { return callback(null); }
-
-  self.datafileSize += newDocs.length;
-
-  newDocs.forEach(function (doc) {
-    toPersist += model.serialize(doc) + '\n';
-  });
-
-  if (toPersist.length === 0) { return callback(null); }
-
-  fs.appendFile(self.filename, toPersist, 'utf8', function (err) {
-    return callback(err);
-  });
-};
-Datastore.prototype.persistNewState = function (newDocs, cb) {
-  if (this.inMemoryOnly) {
-    cb();
-  } else {
-    this._persistNewState(newDocs, cb);
-  }
-};
 
 
 /**
@@ -411,7 +361,7 @@ Datastore.prototype._insert = function (newDoc, cb) {
   // Insert in all indexes (also serves to ensure uniqueness)
   try { self.addToIndexes(insertedDoc); } catch (e) { return callback(e); }
 
-  this.persistNewState([newDoc], function (err) {
+  this.persistence.persistNewState([newDoc], function (err) {
     if (err) { return callback(err); }
     return callback(null, newDoc);
   });
@@ -546,7 +496,7 @@ Datastore.prototype._update = function (query, updateQuery, options, cb) {
       return callback(err);
     }
 
-    self.persistNewState(updatedDocs, function (err) {
+    self.persistence.persistNewState(updatedDocs, function (err) {
       if (err) { return callback(err); }
       return callback(null, numReplaced);
     });
@@ -591,7 +541,7 @@ Datastore.prototype._remove = function (query, options, cb) {
     });
   } catch (err) { return callback(err); }
 
-  self.persistNewState(removedDocs, function (err) {
+  self.persistence.persistNewState(removedDocs, function (err) {
     if (err) { return callback(err); }
     return callback(null, numRemoved);
   });
@@ -602,5 +552,4 @@ Datastore.prototype.remove = function () {
 
 
 
-
 module.exports = Datastore;

lib/persistence.js

@@ -0,0 +1,72 @@
+/**
+ * Handle every persistence-related task
+ */
+
+var fs = require('fs')
+  , path = require('path')
+  , model = require('./model')
+  , customUtils = require('./customUtils')
+  ;
+
+
+/**
+ * Create a new Persistence object for database options.db
+ * @param {Datastore} options.db
+ */
+function Persistence (options) {
+  this.db = options.db;
+}
+
+
+/**
+ * Persist cached database
+ * This serves as a compaction function since the cache always contains only the number of documents in the collection
+ * while the data file is append-only so it may grow larger
+ * @param {Function} cb Optional callback, signature: err
+ */
+Persistence.prototype.persistCachedDatabase = function (cb) {
+  var callback = cb || function () {}
+    , toPersist = ''
+    ;
+
+  this.db.getAllData().forEach(function (doc) {
+    toPersist += model.serialize(doc) + '\n';
+  });
+
+  if (toPersist.length === 0) { return callback(null); }
+
+  fs.writeFile(this.db.filename, toPersist, function (err) { return callback(err); });
+};
+
+
+/**
+ * Persist new state for the given newDocs (can be insertion, update or removal)
+ * Use an append-only format
+ * @param {Array} newDocs Can be empty if no doc was updated/removed
+ * @param {Function} cb Optional, signature: err
+ */
+Persistence.prototype.persistNewState = function (newDocs, cb) {
+  var self = this
+    , toPersist = ''
+    , callback = cb || function () {}
+    ;
+
+  // In-memory only datastore
+  if (self.db.inMemoryOnly) { return callback(null); }
+
+  self.db.datafileSize += newDocs.length;
+
+  newDocs.forEach(function (doc) {
+    toPersist += model.serialize(doc) + '\n';
+  });
+
+  if (toPersist.length === 0) { return callback(null); }
+
+  fs.appendFile(self.db.filename, toPersist, 'utf8', function (err) {
+    return callback(err);
+  });
+};
+
+
+// Interface
+module.exports = Persistence;