This document provides an overview of ZeroMQ, an open-source messaging library that provides sockets for various messaging patterns like request-reply, publish-subscribe, and push-pull. It discusses how ZeroMQ implements these patterns without a centralized broker through intelligent message batching and transport. Examples are given of how ZeroMQ is used in production systems and how it compares to brokered messaging systems. The document concludes with discussing other open-source messaging projects.

1. What is ZeroMQ?
Rajan Bhatt
1/10/2014

2. What are we going to cover?
• What is Messaging?
• ZeroMQ v/s other Messaging solution
• Basics of ZeroMQ
• Coding examples
• Quiz

3. What is Enterprise Messaging ?
• Enterprise messaging is a design pattern for
loosely coupled system to communicate
asynchronously.
• This type of architecture is foundation for
“shared-nothing” model.
• Great example of this model in computation is
also known as “Actor Model”.

4. Broad classification of Messaging
System
• Broker based Messaging System.
– AMQP based system, Implementation RabbitMQ,
ActiveMQ
– JMS – Java Message Service.
– STOMP – The Simple Text Oriented Messaging
Protocol
– MQTT – Light Weight protocol for Sensor networks
• Broker-less Messaging system – ZeroMQ,
Nanomsg etc.

5. AMQP – RabbitMQ
• RabbitMQ is open source message broker
software that implements the Advanced
Message Queuing protocol. This is written in
Erlang language.
• Basic components of AMQP
Producer, Exchange, Queue and Consumer

6. Basic AMQP Model
Publisher
Routes
Exchange
Queue
Queue
Consumer n
Routes
Publishes
Consumes Consumer 1
Consumes

7. In Nutshell - ZeroMQ
• Not MOM ( no broker, no queues, etc..)
• “Super” Socket library that acts as concurrency framework
• Carries messages across various transport, inproc, IPC, TCP
and multicast.
• Connect N-to-N via fan-out, pub-sub, pipeline. Request-reply.
• Asynchronous I/O for scalable multicore message-passing
apps.
• 40+ languages including C. C++, JAVA, .NET, Python.

8. In Nutshell - ZeroMQ..
• Is a library that supports certain network
communication patterns using socket.
• The “MQ” part comes in because ZeroMQ
uses queues internally to buffer messages so
that you don’t block your application when
sending data.
• When you say, socket.send(…), ZeroMQ
actually enqueues a messages to be sent later
by a dedicated communication thread.

9. In nutshell - ZeroMQ
• It does not have overhead of an over-
engineered protocol such AMQP
• It can make use of efficient transports such as
reliable multicast or Y-suite IPC ytansport
• It makes use of intelligent message batching.
This allows ZMQ to efficiently utilize a TCP/IP
connection by minimizing not only protocol
overhead but system calls.

10. ZeroMQ – Message Encapsulation
• Encapsulates communication into Messages
which may be composed of multiple parts.
• Rather than asking ZeroMQ to receive certain
number od f bytes from socket, you ask
ZeroMQ to receive a single message.

11. ZeroMQ - Scalability
• A single ZeroMQ socket can for example connect
to multiple end points and automatically load
balance messages over them or it can work as
some sort of Fan-in, collecting messages from
sources through a single socket.
• ZeroMQ follows brokerless design so there is no
single point of failure. Combine this with the
simplicity and performance and you get
something that you can use to make your
application distributed.

12. ZeroMQ Socket – Request- Reply
Pattern
• Most basic pattern is client/server model,
where a client sends a request and server
replies to that request.
• But…
• Request type of socket can connect to many
servers and request would be distributes to all
connected server.

13. ZeroMQ Request-Reply Socket Pattern depiction
Zmq client Zmq servers
REQ REP
REP
Request # 1
Request # 2
Reply #1
Reply # 2
Requests are load balanced across server
REP
REP

14. Demo
• ZMQ Request/Reply Pattern

15. ZeroMQ – Pub-Sub Pattern
– Publish/Subscribe is classic pattern where senders
of messages, called publisher do not program the
messages to be sent directly to specific receives,
called subscribers. Messages are published
without knowledge of what or if any subscribes
exists.

16. Pub-Sub Socket Depiction
ZeroMQ Bus
Pub Socket-1
Sub Socket-3Sub Socket-2Sub Socket-1
Pub Socket-2
Publisher sockets are unaware of number of Subscribers. Subscriber socket can
subscribe to multiple of Publisher Socket.

17. Demo
• ZMQ Publisher/Subscriber Demo

18. ZeroMQ Socket – Push/Pull Pattern
• Push and Pull sockets let you distribute
messages to multiple workers arranged in
pipeline. A Push socket will distribute sent
messages to its all Pull clients evenly. This is
equivalent to producer/consumer model but
the results computed by consumers are not
sent upstream but downstream to another
pull/consumer socket.

19. ZeroMQ Push-Pull Pattern
Producer Consumers Result Collector
PUSH
PULL
PULL
PULL
PUSH
PUSH
PUSH
PULL

20. Demo
• ZMQ Push/Pull Socket demo

21. ZMQ Devices
• ZMQ – sockets are either bind or connect
• General pattern is stable part (server) bind
and dynamic part connects to it.
• What do you do when both parts are dynamic
?
• Enter ZMQ device

22. Types of Devices..
• Queue
• Forwarder
• Streamer

23. Client
Client
Client
ZMQ Device
Server
Server
Server
Moving Part Moving Part
Stable Part
These devises can bind to 2 different ports and forward messages from one end to
The other. The forwarding device can become stable point in your network where
Each component can connect to.

24. Queue Device
REQ
REQ
REQ
REP
REP
REP
Queue
XREP XREQ
This is the intermediary that sits between clients and servers, forwarding request to
server and relaying replies back to client. The ZMQ device takes (ZMQ.QUEUE) and
The two sockets bound to well known ports. This is Request/Response broker.

25. Forwarding Device
PUB
PUB
PUB
SUB
SUB
SUB
Forwarder
XREP XREQ
Just like Queue, Which is like the request-reply broker, For forwarder like the pub-sub
Proxy server. It allows both publishers and subscribers to be moving parts and it self
becomes stable hub interconnecting them. FORWARDER collects messages from set of
Publishers to and forwards these to a set of subscribers.

26. Who is using ZeroMQ in production
• Storm platform – communication channel
between spouts and bolt.
• Loggly – Cloud based logging platform
• Dotcloud – Open source RPC platform called
ZeroRPC based on ZeroMQ messaging.
• This is very popular messaging framework for
high frequency financial trading.

27. Which Messaging is better ? Brokered
or Broker-less
• Both messaging patterns have advantages and
disadvantages.
• In Enterprise, we see both being used to solve
messaging problem which are
multidimensional.
• ZeroMQ out-performs other messaging
solution in performance, as it is bare-bone
framework

28. Which are other Interesting Open
Source Messaging project ?
• Kafka – LinkedIn’s open source message bus,
Apache project, used by Tweeter also and
many many companies
• NullMQ – Operates over WebSocket, on
communication protocol based on STOMP.
ZeroMQ semantics in Web Browser.
• NanoMSG-

29. I know you have questions…
• I may not have answer.. But please ask..
• I will find out answers If I don’t know…

30. Please provide feedback
• Rajan.Bhatt@disney.com..
• Have Fun with ZeroMQ and all messaging..