Simplify mutex lock

lib/model.js

@@ -3,14 +3,14 @@
 var EventEmitter = require('events').EventEmitter;
 var _ = require('lodash');
 var Promise = require('bluebird');
-var ReadWriteLock = require('rwlock');
 var util = require('./util');
 var Document = require('./document');
 var Query = require('./query');
 var Schema = require('./schema');
 var Types = require('./types');
 var WarehouseError = require('./error');
 var PopulationError = require('./error/population');
+var Mutex = require('./mutex');
 
 var parseArgs = util.parseArgs;
 var reverse = util.reverse;
@@ -71,7 +71,7 @@ function Model(name, schema_) {
    * @property {Object} locks
    * @private
    */
-  this._lock = new ReadWriteLock();
+  this._mutex = new Mutex();
 
   /**
    * Schema.
@@ -195,15 +195,12 @@ function execHooks(schema, type, event, data) {
 }
 
 Model.prototype._acquireWriteLock = function(id) {
-  var lock = this._lock;
+  var mutex = this._mutex;
 
   return new Promise(function(resolve, reject) {
-    lock.async.writeLock(id, function(err, release) {
-      if (err) return reject(err);
-      resolve(release);
-    });
-  }).disposer(function(release) {
-    release();
+    mutex.lock(resolve);
+  }).disposer(function() {
+    mutex.unlock();
   });
 };
 

lib/mutex.js

@@ -0,0 +1,30 @@
+'use strict';
+
+function Mutex() {
+  this._locked = false;
+  this._queue = [];
+}
+
+Mutex.prototype.lock = function(fn) {
+  if (this._locked) {
+    this._queue.push(fn);
+    return;
+  }
+
+  this._locked = true;
+  fn();
+};
+
+Mutex.prototype.unlock = function() {
+  if (!this._locked) return;
+
+  var next = this._queue.shift();
+
+  if (next) {
+    next();
+  } else {
+    this._locked = false;
+  }
+};
+
+module.exports = Mutex;

package.json

@@ -25,8 +25,7 @@
     "bluebird": "^3.0.5",
     "cuid": "~1.3.8",
     "graceful-fs": "^4.1.2",
-    "lodash": "^3.10.1",
-    "rwlock": "^5.0.0"
+    "lodash": "^3.10.1"
   },
   "devDependencies": {
     "chai": "^3.4.1",

test/index.js

@@ -23,4 +23,5 @@ describe('Warehouse', function() {
   require('./scripts/types/string');
   require('./scripts/types/virtual');
   require('./scripts/util');
+  require('./scripts/mutex');
 });

test/scripts/model.js

@@ -176,9 +176,9 @@ describe('Model', function() {
 
     Test = db.model('Test', testSchema);
 
-    return Test.insert([
-      {id: 1},
-      {id: 1}
+    return Promise.all([
+      Test.insert({id: 1}),
+      Test.insert({id: 1})
     ]).should.eventually.be.rejected;
   });
 

test/scripts/mutex.js

@@ -0,0 +1,33 @@
+'use strict';
+
+var should = require('chai').should(); // eslint-disable-line
+var Mutex = require('../../lib/mutex');
+var sinon = require('sinon');
+
+describe('Mutex', function() {
+  it('mutex test', function(callback) {
+    var mutex = new Mutex();
+    var fn1, fn2;
+
+    fn1 = sinon.spy(function() {
+      setTimeout(function() {
+        fn2.called.should.be.false;
+        mutex.unlock();
+      }, 20);
+    });
+
+    fn2 = sinon.spy(function() {
+      fn1.calledOnce.should.be.true;
+      mutex.unlock();
+    });
+
+    mutex.lock(fn1);
+    mutex.lock(fn2);
+
+    mutex.lock(function() {
+      fn1.calledOnce.should.be.true;
+      fn2.calledOnce.should.be.true;
+      callback();
+    });
+  });
+});