NodeJS Package-UUID IDX AMQPLIB

NodeJS Package-UUID IDX AMQPLIB

UUID
https://github.com/kelektiv/node-uuid
Support version 1, 3, 4, 5 UUIDs

Current latest version is
> npm info uuid version
3.2.1

Install that library in global
> sudo npm install -g uuid

Generate UUID
>uuid
a63b5d3b-b80a-480b-ab56-8ba7bb043d68
>uuid v1
1ea16090-3bfc-11e8-9d47-9194247d340e

In the TypeScript Code, first of all, configure TypeScript Support on Sublime Text3
https://cmatskas.com/getting-started-with-typescript-and-sublime-text/
Package Control —> Install Package —> TypeScript

import * as uuidv4 from 'uuid/v4';
//version 4 is random
const meetingUuid = paramsToSend.UUID = uuidv4();

IDX
https://github.com/facebookincubator/idx
Traverse properties on objects and arrays.

Current Version
> npm info idx version
2.2.0

From Readme
type User = {
    user: ?{
        name: string,
        friends: ?Array<User>,
    }
};

props.user && props.user.friends && props.user.friends[0] && props.user.friends[0].friends, my first friends’s friends

Import idx from ‘idx’;
idx(props, _ => _.user.friends[0].friends)

APIGatewayEvent event;
const loginSession = idx(event, _ => { return (_ as any).loginSession; } );

AMQP.NODE
amqplib https://github.com/squaremo/amqp.node
Current Version
> npm info amqplib version
0.5.2

We are using CallbackAPI in our Project
var q = 'tasks';

function bail(err) {
  console.error(err);
  process.exit(1);
}

// Publisher
function publisher(conn) {
  conn.createChannel(on_open);
  function on_open(err, ch) {
    if (err != null) bail(err);
    ch.assertQueue(q);
    ch.sendToQueue(q, new Buffer('something to do'));
  }
}

// Consumer
function consumer(conn) {
  var ok = conn.createChannel(on_open);
  function on_open(err, ch) {
    if (err != null) bail(err);
    ch.assertQueue(q);
    ch.consume(q, function(msg) {
      if (msg !== null) {
        console.log(msg.content.toString());
        ch.ack(msg);
      }
    });
  }
}

require('amqplib/callback_api')
  .connect('amqp://localhost', function(err, conn) {
    if (err != null) bail(err);
    consumer(conn);
    publisher(conn);
  });

Promise API
Ignore, not that clear to me.

Detail in Example
https://segmentfault.com/a/1190000008229467
https://www.rabbitmq.com/tutorials/tutorial-one-javascript.html

More Complex One
https://www.cloudamqp.com/blog/2015-05-19-part2-2-rabbitmq-for-beginners_example-and-sample-code-node-js.html

Reconnect when There is Error
function start() {
    amqp.connect(process.env.CLOUDAMQP_URL + “?heartbeat=60”, function(err, conn) {
        if (err) {
            console.error(“{AMQP]”, err.message);
            return setTimeout(start, 1000);
        }
        conn.on(“error”, function(err) {
            if (err.message !== “Connection closing”) {
                console.error(“[AMQP] conn error”, err.message);
            }
        });
        conn.on(“close”, function() {
            console.error(“[AMQP] reconnecting”);
            return setTimeout(start, 1000);
        });
        console.log(“[AMQP] connected”);
        amqpConn = conn;
        whenConnected();
    });
}

function whenConnected() {
    startPublisher();
    startWorker();
}

Publisher
var pubChannel = null;
var offlinePubQueue = [];
function startPublisher() {
  amqpConn.createConfirmChannel(function(err, ch) {
    if (closeOnErr(err)) return;
      ch.on("error", function(err) {
      console.error("[AMQP] channel error", err.message);
    });
    ch.on("close", function() {
      console.log("[AMQP] channel closed");
    });

    pubChannel = ch;
    while (true) {
      var m = offlinePubQueue.shift();
      if (!m) break;
      publish(m[0], m[1], m[2]);
    }
  });
}

function publish(exchange, routingKey, content) {
  try {
    pubChannel.publish(exchange, routingKey, content, { persistent: true },
                      function(err, ok) {
                        if (err) {
                          console.error("[AMQP] publish", err);
                          offlinePubQueue.push([exchange, routingKey, content]);
                          pubChannel.connection.close();
                        }
                      });
  } catch (e) {
    console.error("[AMQP] publish", e.message);
    offlinePubQueue.push([exchange, routingKey, content]);
  }
}

Publish fails, it will put the message back to the internal queue.

Consumer
// A worker that acks messages only if processed successfully
function startWorker() {
  amqpConn.createChannel(function(err, ch) {
    if (closeOnErr(err)) return;
    ch.on("error", function(err) {
      console.error("[AMQP] channel error", err.message);
    });
    ch.on("close", function() {
      console.log("[AMQP] channel closed");
    });

    ch.prefetch(10);
    ch.assertQueue("jobs", { durable: true }, function(err, _ok) {
      if (closeOnErr(err)) return;
      ch.consume("jobs", processMsg, { noAck: false });
      console.log("Worker is started");
    });
  });
}

function processMsg(msg) {
  work(msg, function(ok) {
    try {
      if (ok)
        ch.ack(msg);
      else
        ch.reject(msg, true);
    } catch (e) {
      closeOnErr(e);
    }
  });
}

function work(msg, cb) {
  console.log("PDF processing of ", msg.content.toString());
  cb(true);
}

Other Methods
function closeOnErr(err) {
  if (!err) return false;
  console.error("[AMQP] error", err);
  amqpConn.close();
  return true;
}

Main Methods
setInterval(function() {
  publish("", "jobs", new Buffer("work work work"));
}, 1000);

start();

References:
https://github.com/kelektiv/node-uuid
https://github.com/facebookincubator/idx
https://www.npmjs.com/package/idx

https://www.cloudamqp.com/blog/2015-05-18-part1-rabbitmq-for-beginners-what-is-rabbitmq.html
https://www.cloudamqp.com/blog/2015-05-19-part2-2-rabbitmq-for-beginners_example-and-sample-code-node-js.html
https://github.com/squaremo/amqp.node