Revert "undo initial RedisShardingClient". decided to keep it but make simpler.

pulled in partial work from redis-sharding branch, will continue on master.

Author: Ben Buckman

README.md

@@ -71,7 +71,4 @@ Now use `sentinelClient` as a regular client: `set`, `get`, `hmset`, etc.
 
 # `RedisShardingClient`
 
-**We decided to abandon this after starting to build it.** The concept was another abstraction layer that behaved transparently like a `RedisClient`, but handled sharding (on key) in the background between a ring of multiple clients.
-For our particular application (or any particular application), however, the complexity such an abstraction layer involves is not worth the trouble, and a much simpler application-specific abstraction makes a lot more sense.
-
-If anyone is interested in continuing this line of development, see the [sharding-client](https://github.com/DocuSignDev/node_redis/tree/sharding-client) branch.
+To be continued...

index.js

@@ -1113,6 +1113,12 @@ var Sentinel = require('./lib/sentinel');
 exports.RedisSentinelClient = Sentinel.RedisSentinelClient;
 
 
+// sharding client. instantiate separately.
+var Sharding = require('./lib/sharding');
+exports.RedisShardingClient = Sharding.RedisShardingClient;
+
+
+
 exports.createClient = function (port_arg, host_arg, options) {
     var redis_client;
     var net_client;

lib/sharding.js

@@ -0,0 +1,137 @@
+/**
+[Ben Buckman @ DocuSign]
+
+Adds Redis sharding support, via RedisShardingClient.
+Modeled on the RedisSentinelClient (also added in our fork).
+
+(see readme for notes)
+*/
+
+var RedisSingleClient = require('../index'),
+    events = require('events'),
+    util = require('util'),
+    reply_to_object = require('./utils').reply_to_object,
+    commands = RedisSingleClient.commands,
+    to_array = require('./to_array');
+
+
+/*
+options:
+- `clients`: array of RedisClients (or RedisSentinelClients)
+- logger (e.g. winston)
+- debug (boolean)
+*/
+function RedisShardingClient(options) {
+  events.EventEmitter.call(this);
+
+  this.options = options || {};
+
+  this.clients = this.options.clients;
+  if (!this.clients || !Array.isArray(this.clients) || !this.clients.length) {
+    throw new Error("RedisShardingClient needs an array of individual clients");
+  }
+
+  // hashFunction should take (key, num) and return an integer between 0..(num-1)
+  this.hashFunction = this.options.hashFunction;
+  if (typeof this.hashFunction !== 'function') {
+    throw new Error("RedisShardingClient needs a hashFunction.");
+  }
+
+  // @todo pass thru methods, parsing out keys.
+
+  // @todo static numeric properties, pass thru the total of all clients?
+
+  this.waitForConnected();
+  this.waitForReady();
+}
+
+util.inherits(RedisShardingClient, events.EventEmitter);
+
+
+// helper, and for testing: get index of client to use, based on key.
+RedisShardingClient.prototype.clientIndexFor = function clientIndexFor(key) {
+  return clientInd = this.hashFunction(key, this.clients.length);
+};
+
+// get a single client based on key.
+RedisShardingClient.prototype.clientFor = function clientFor(key) {
+  var clientInd = this.clientIndexFor(key);
+  return this.clients[clientInd];
+};
+
+
+// helper to wait for all clients to be ready.
+RedisShardingClient.prototype.waitForReady = function waitForReady() {
+  var self = this;
+  var needCount = this.clients.length;
+
+  self.ready = false;
+
+  var onAllReady = function() {
+    needCount--;
+    if (needCount === 0) {
+      self.debug("All sub-clients are ready");
+      self.ready = true;
+      self.emit("ready");
+    }
+  };
+
+  this.clients.forEach(function(client){
+    if (client.ready === true) onAllReady();
+    else client.on('ready', onAllReady);
+  });
+
+
+  // @todo follow subsequent ready=false states? bubble up?
+};
+
+
+// helper to wait for all clients to be ready.
+RedisShardingClient.prototype.waitForConnected = function waitForConnected() {
+  var self = this;
+  var needCount = this.clients.length;
+
+  self.connected = false;
+
+  var onAllConnected = function() {
+    needCount--;
+    if (needCount === 0) {
+      self.debug("All sub-clients are connected");
+      self.connected = true;
+      self.emit("connect");
+    }
+  };
+
+  this.clients.forEach(function(client){
+    if (client.connected === true) onAllConnected();
+    else client.on('connect', onAllConnected);
+  });
+
+  // @todo follow subsequent disconnect events?
+};
+
+
+// @todo implement 'end'?
+
+
+
+
+// @TODO this is duplicated between sentinal and sharding, consolidate.
+// log(type, msgs...)
+// type is 'info', 'error', 'debug' etc
+RedisShardingClient.prototype.log = function log() {
+  var logger = this.options.logger || console;
+  var args = Array.prototype.slice.call(arguments);
+  logger.log.apply(logger, args);
+};
+// debug(msgs...)
+RedisShardingClient.prototype.debug = function debug() {
+  if (this.options.debug) {
+    var args = ['debug'].concat(Array.prototype.slice.call(arguments));
+    this.log.apply(this, args);
+  }
+};
+
+
+
+exports.RedisShardingClient = RedisShardingClient;

test/test_sentinel.js

@@ -21,18 +21,7 @@ var testUtils = require('./utils'),
     require_error = testUtils.require_error,
     require_number = testUtils.require_number;
 
-
-function MockLogger(){
-  var self = this;
-  this.msgs = [];
-  this.toConsole = false;
-}
-MockLogger.prototype.log = function() {
-  var args = Array.prototype.slice.call(arguments);
-  this.msgs.push(args);
-  if (this.toConsole) console.log.apply(this, args);
-};
-
+var MockLogger = testUtils.MockLogger;
 
 
 describe('RedisSentinelClient', function(){