Initial commit with code from https://gist.github.com/eveiga/5039007 …

…wrapped in an npm module

.gitignore

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+/node_modules
+/*.tgz

README.md

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+# Redis-Twemproxy Agent
+
+This originally started as a [gist](https://gist.github.com/eveiga/5039007) posted on [a twemproxy ticket about doing HA redis](https://github.com/twitter/twemproxy/issues/67).
+
+Edgar was nice enough to share what he had so far and now I'm trying to take it a bit further in hopes of making a generalized package.

bin/redis_twemproxy_agent

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+#!/usr/bin/env node
+
+var path = require('path');
+require(path.join(__dirname,'../lib/cli.js'));

lib/agent.js

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+var fs   = require('fs'),
+    exec = require('child_process').exec,
+    path = require('path'),
+    os   = require('os');
+
+var Sentinel   = require("node-sentinel"),
+    _          = require("underscore"),
+    async      = require("async"),
+    nodemailer = require("nodemailer");
+
+function Agent(config){
+  if(!_.isObject(config)){
+    return console.error("Bad config");
+  }
+
+  this.nutcracker_config_file = config.nutcracker_config_file;
+  this.redis_sentinel_ip = config.redis_sentinel_ip;
+  this.redis_sentinel_port = config.redis_sentinel_port;
+  this.log = "";
+}
+
+Agent.prototype.restart_nutcracker = function(callback){
+  var self = this;
+  var child = exec(
+    "/etc/init.d/nutcracker restart",
+    function(error, stdout, stderr) {
+      self.log += "<h2>Nutcracker restarted with outuput:</h2>";
+      self.log += "<div><pre>"+stdout+"</pre></div>";
+
+      if (error !== null) {
+        self.log += "<h2>Nutcracker failed restarting with error:</h2>";
+        self.log += "<div><pre>"+error+"</pre></div>";
+      }
+      return callback();
+    }
+  );
+};
+
+Agent.prototype.update_nutcracker_config = function(data, callback){
+  var old_content = fs.readFileSync(this.nutcracker_config_file, 'utf8');
+
+  var new_content = old_content.replace(
+    data.details["old-ip"]+":"+data.details["old-port"],
+    data.details["new-ip"]+":"+data.details["new-port"]
+  );
+
+  fs.writeFileSync(this.nutcracker_config_file, new_content, 'utf8');
+
+  this.log += "<h2>Nutcracker config updated with new content:</h2>";
+  this.log += "<div><pre>"+new_content+"</pre></div>";
+
+  return callback();
+};
+
+Agent.prototype.send_mail = function() {
+  var self = this;
+  var transport = nodemailer.createTransport("Sendmail");
+
+  var mailOptions = {
+    from: "from@mail.com",
+    to: "to@mail.com",
+    subject: "Warning: Nutcracker restarted forced on "+os.hostname(),
+    generateTextFromHTML: true,
+    html: "<h1>Nutcracker was restarted due to master switch in redis configuration.</h1>" + this.log
+  };
+
+  transport.sendMail(mailOptions, function(error, responseStatus){
+    self.log = "";
+    if(error) {
+      return console.error(error);
+    }
+
+    return console.info(
+      responseStatus.message+"\n"+responseStatus.messageId
+    );
+  });
+};
+
+Agent.prototype.switch_master_handler = function(){
+  var self = this;
+  return function(data) {
+    async.series([
+                 function(callback) {
+      self.update_nutcracker_config(data, callback);
+    },
+    function(callback) {
+      self.restart_nutcracker(callback);
+    }
+    ],
+    function(){
+      return self.send_mail();
+    });
+  };
+};
+
+Agent.prototype.start_sentinel = function(){
+  this.sentinel = new Sentinel(
+    this.redis_sentinel_ip, this.redis_sentinel_port
+  );
+
+  this.sentinel.on("switch-master", this.switch_master_handler());
+};
+
+Agent.prototype.check_nutcracker_config = function(cb){
+  fs.appendFile(this.nutcracker_config_file, "", cb);
+};
+
+Agent.prototype.bootstrap = function(){
+  var self = this;
+
+  this.check_nutcracker_config(
+    function(error){
+    if(error) {
+      return console.error("Nutcracker config file: "+error);
+    }
+
+    return self.start_sentinel();
+  }
+  );
+};
+
+module.exports = Agent;

lib/cli.js

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+var util = require('util');
+
+util.puts("The CLI will go here");

package.json

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+{
+  "name": "redis_twemproxy_agent",
+  "version": "0.0.1",
+  "description": "Redis agent for nutcracker update",
+  "preferGlobal": true,
+  "bin": "bin/redis_twemproxy_agent",
+  "main": "lib/agent.js",
+  "scripts": {
+    "test": "jshint lib spec && jasmine-node spec"
+  },
+  "repository": {
+    "type": "git",
+    "url": "https://github.com/matschaffer/redis_twemproxy_agent.git"
+  },
+  "keywords": [
+    "redis",
+    "twemproxy",
+    "ha"
+  ],
+  "author": "Edgar Veiga <edgarmveiga@gmail.com>",
+  "contributors": [
+    "Mat Schaffer <mat@schaffer.me>"
+  ],
+  "license": "BSD",
+  "dependencies": {
+    "node-sentinel": "0.0.4",
+    "underscore": "~1.4.4",
+    "async": "~0.2.5",
+    "nodemailer": "~0.3.42"
+  },
+  "devDependencies": {
+    "jshint": "~1.0.0",
+    "jasmine-node": "~1.3.0"
+  }
+}

spec/agent_spec.js

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+var Agent = require("../lib/agent.js");
+
+describe("Redis Twemproxy Agent", function() {
+  it("subscribes to master switch notifications");
+  it("swaps old master information with new master information");
+  it("restarts twemproxy");
+});