app.portBindings and newManifest.tcpPorts may be null

src/locker.js

@@ -0,0 +1,55 @@
+'use strict';
+
+var assert = require('assert'),
+    debug = require('debug')('box:locker'),
+    EventEmitter = require('events').EventEmitter,
+    util = require('util');
+
+function Locker() {
+    this._operation = null;
+    this._timestamp = null;
+    this._watcherId = -1;
+}
+util.inherits(Locker, EventEmitter);
+
+// these are mutually exclusive operations
+Locker.prototype.OP_BOX_UPDATE = 'box_update';
+Locker.prototype.OP_FULL_BACKUP = 'full_backup';
+Locker.prototype.OP_APPTASK = 'apptask';
+Locker.prototype.OP_MIGRATE = 'migrate';
+
+Locker.prototype.lock = function (operation) {
+    assert.strictEqual(typeof operation, 'string');
+
+    if (this._operation !== null) return new Error('Already locked for ' + this._operation);
+
+    this._operation = operation;
+    this._timestamp = new Date();
+    var that = this;
+    this._watcherId = setInterval(function () { debug('Lock unreleased %s', that._operation); }, 1000 * 60 * 5);
+
+    debug('Acquired : %s', this._operation);
+
+    this.emit('locked', this._operation);
+
+    return null;
+};
+
+Locker.prototype.unlock = function (operation) {
+    assert.strictEqual(typeof operation, 'string');
+
+    if (this._operation !== operation) throw new Error('Mismatched unlock. Current lock is for ' + this._operation); // throw because this is a programming error
+
+    debug('Released : %s', this._operation);
+
+    this._operation = null;
+    this._timestamp = null;
+    clearInterval(this._watcherId);
+    this._watcherId = -1;
+
+    this.emit('unlocked', operation);
+
+    return null;
+}
+
+exports = module.exports = new Locker();