feat(redis): support readonly mode for cluster

Author: luin

API.md

@@ -62,6 +62,7 @@ Creates a Redis instance
 | [options.keyPrefix] | <code>string</code> | <code>&quot;&#x27;&#x27;&quot;</code> | The prefix to prepend to all keys in a command. ```javascript var redis = new Redis({ lazyConnect: true }); // No attempting to connect to the Redis server here. // Now let's connect to the Redis server redis.get('foo', function () { }); ``` |
 | [options.retryStrategy] | <code>function</code> |  | See "Quick Start" section |
 | [options.reconnectOnError] | <code>function</code> |  | See "Quick Start" section |
+| [options.readOnly] | <code>boolean</code> | <code>false</code> | Enable READONLY mode for the connection. Only available for cluster mode. |
 
 **Example**  
 ```js

lib/redis.js

@@ -72,6 +72,8 @@ var ScanStream = require('./scan_stream');
  * ```
  * @param {function} [options.retryStrategy] - See "Quick Start" section
  * @param {function} [options.reconnectOnError] - See "Quick Start" section
+ * @param {boolean} [options.readOnly=false] - Enable READONLY mode for the connection.
+ * Only available for cluster mode.
  * @extends [EventEmitter](http://nodejs.org/api/events.html#events_class_events_eventemitter)
  * @extends Commander
  * @example
@@ -166,7 +168,8 @@ Redis.defaultOptions = {
   autoResendUnfulfilledCommands: true,
   lazyConnect: false,
   keyPrefix: '',
-  reconnectOnError: null
+  reconnectOnError: null,
+  readOnly: false
 };
 
 Redis.prototype.resetCommandQueue = function () {

lib/redis/event_handler.js

@@ -128,6 +128,11 @@ exports.readyHandler = function (self) {
       self.client('setname', self.options.connectionName);
     }
 
+    if (self.options.readOnly) {
+      debug('set the connection to readonly mode');
+      self.readonly();
+    }
+
     if (self.prevCondition) {
       var condition = self.prevCondition;
       self.prevCondition = null;

test/functional/connection.js

@@ -142,32 +142,50 @@ describe('connection', function () {
   describe('connectionName', function () {
     it('shoud name the connection if options.connectionName is not null', function (done) {
       var redis = new Redis({ connectionName: 'niceName' });
-      redis.once('ready', function() {
-        redis.client('getname', function(err, res) {
+      redis.once('ready', function () {
+        redis.client('getname', function (err, res) {
           expect(res).to.eql('niceName');
           done();
         });
       });
       redis.set('foo', 1);
     });
 
-    it('should set the name before any subscribe command if reconnected', function(done) {
+    it('should set the name before any subscribe command if reconnected', function (done) {
       var redis = new Redis({ connectionName: 'niceName' });
-      var pub = new Redis();
       redis.once('ready', function () {
-        redis.subscribe('l', function() {
+        redis.subscribe('l', function () {
           redis.disconnect(true);
-          redis.unsubscribe('l', function() {
-            redis.client('getname', function(err, res) {
-             expect(res).to.eql('niceName');
-             done();
-           });              
+          redis.unsubscribe('l', function () {
+            redis.client('getname', function (err, res) {
+              expect(res).to.eql('niceName');
+              done();
+            });
           });
         });
       });
     });
   });
 
+  describe('readOnly', function () {
+    it('shoud send readonly command before other commands', function (done) {
+      var called = false;
+      var redis = new Redis({ port: 30001, readOnly: true, showFriendlyErrorStack: true });
+      var node = new MockServer(30001, function (argv) {
+        if (argv[0] === 'readonly') {
+          called = true;
+        } else if (argv[0] === 'get' && argv[1] === 'foo') {
+          expect(called).to.eql(true);
+          redis.disconnect();
+          node.disconnect(function () {
+            done();
+          });
+        }
+      });
+      redis.get('foo').catch(function () {});
+    });
+  });
+
   describe('autoResendUnfulfilledCommands', function () {
     it('should resend unfulfilled commands to the correct db when reconnected', function (done) {
       var redis = new Redis({ db: 3 });