This document provides an overview of using a JMS (Java Message Service) implementation like Apache ActiveMQ for asynchronous event processing in a ranker system. It discusses why messaging is useful, challenges in selecting a JMS provider and ActiveMQ, how JMS and point-to-point messaging works, key ActiveMQ features, and some other JMS provider options.
2. Agenda
● Why Event Processing System For Ranker?
● What are challenges?
● General Overview of JMS
● Walk through ActiveMQ
● Why Messaging?
● Other JMS Providers.
3. Why Messaging?
● Asynchronous operation
− A client can schedule work to be done and return
immediately
− A client can be notified in an event-driven fashion when
something has happened
● Loose Coupling
− Systems connected via messaging need not be aware
of each other, or use the same technologies
− Key messages can easily be routed to many systems
− Message broker is buffer in case of downtime
4. Why Messaging?
● Fire and Forget
− Message Broker can guarantee messages are
recorded and delivered even vs. crashes
● Parallelize Work
− Messages in a single stream can be handled in
parallel by many client threads or systems
● Throttle Work
− A large amount of work can be split into a small
number of threads or systems to throttle effort (e.g. due to
licensing restrictions)
5. Why Event Processing System For Ranker?
● Ranker has a lot of complicated algorithms running behind
and user really does not need to wait till the execution of all
the algorithms.
● You may wish to implement this because the request take a
long time to complete or because several parties may be
interested in the actual request
● Eg: Crowd ranked/Vote ranked List aggregation (This
algorithm may take 1- 5 mts to complete depends of user
contribution.)
● Email sending functionality.
● Moderation of user input (eg. Bad word filtering)
● List Auto tagging.
6. What are the challenges?
● Selecting the JMS provider
− We are running the app based on Spring 3.0
/Apache tomcat stack, we have to select the
appropriate JMS provider. We selected Apache
ActiveMQ.
● Reasons for selecting ActiveMQ
− Its pretty easy to integrate with Spring Framework.
− Open source project.
− Pretty good documentation available for ActiveMQ as
well as for Integration with spring framework.
7. What is JMS?
● A specification that describes a common way for Java
programs to create, send, receive and read distributed
enterprise messages
● Loosely coupled communication
● Asynchronous messaging
● Reliable delivery
- A message is guaranteed to be delivered once and
only once.
● Outside the specification
- Security services
- Management services
8. A JMS Application
● JMS Clients
- Java programs that send/receive messages
● Messages
- Administered Objects
preconfigured JMS objects created by an admin for the
use of clients
- ConnectionFactory, Destination (queue or topic)
● JMS Provider
- messaging system that implements JMS and
administrative functionality
10. JMS Messaging Domains
● Point-to-Point (PTP)
○ Built around the concept of message queues
○ Each message has only one consumer
● Publish-Subscribe systems
○ Uses a “topic” to send and receive messages
○ Each message has multiple consumers
13. Message Consumptions
● Synchronously
○ A subscriber or a receiver explicitly fetches the message from
the destination by calling the receive method.
○ The receive method can block until a message arrives or can
time out if a message does not arrive within a specified time
limit.
● Asynchronously
○ A client can register a message listener with a consumer.
○ Whenever a message arrives at the destination, the JMS
provider delivers the message by calling the listener's
onMessage() method.
16. More JMS Features
● Durable subscription
● By default a subscriber gets only messages
published on a topic while a subscriber is alive
● Durable subscription retains messages until a they
are received by a subscriber or expire
17. More JMS Features
Difference Between Persistent & Nonpersistent deliveries
− Persistent delivery take cares of reprocessing the
request if the JMS broker restarted before serving the
request, it will use file/db to store the request, this
implementation is costly compare to non persistent delivery.
− Nonpersistent delivery will just ignore the request if
broker restarted while serving the request.
18. About ActiveMQ
● An open-source message broker (compare to JBossMQ,
or many commercial products)
− See http://activemq.apache.org/
● Generally stable and high-performance
● Can be run standalone, or inside another process, app
server, or Java EE application
● Supports everything JMS requires, plus various
extensions
● Integrates well into other products
19. ActiveMQ Message Extensions
● Virtual Destinations (load-balancing and failover for
topics)
● Retroactive Subscriptions (subscriber can receive some
number of previous messages on connect)
● Exclusive Consumers & Message Groups (loadbalancing
and failover while preserving message ordering)
● Mirrored queues (monitor queue messages)
20. ActiveMQ Client Connectivity
● Dictated by the wire protocol a client uses to talk to the
broker
● Generally there are two protocol options – OpenWire
(binary) and Stomp (text)
− OpenWire is the default and has the most history and
best support (including SSL) – for Java, .NET, etc.
− Stomp is easiest to develop for and therefore has the
most cross-language support (Perl, Python, Ruby, ...)
● Also a variety of other special-purpose protocols (Jabber,
adapters for REST/AJAX, etc.)
21. ActiveMQ Persistence Options
● Different strategies available for storing persistent
messages
− to local files, database, etc.
− or both – stored to local files and then periodically batch
undelivered messages to the DB...
● Default implementation changed between ActiveMQ 4.x
and 5.x
● May still customize the persistence engine based on
specific performance requirements
22. ActiveMQ SecurityAnd Management
● OpenWire protocol can use SSL for encryption
● Broker can use authentication (e.g. username/password
required to connect)
− Uses JAAS to identify the back-end user data store
(properties files, DB, LDAP, etc.)
● JMX management enabled by default
− Use a tool like JConsole to monitor queues, etc.
● Web Console available as well
23. ActiveMQ Testing
● ActiveMQ can easily run in an embedded, nonpersistent,
in-VM only mode for unit tests
● Also easily to run ActiveMQ via beans in a Spring context,
if you're testing with Spring
● ActiveMQ includes a simple JNDI provider if you want to
test Java EE code that relies on JNDI lookups to access
JMS resources
● Can use tools like JMeter to load test the broker
24. JMS Providers
● SunONE Message Queue (SUN)
○ A JMS provider integrated with the SunONE
Application Server
○ http://www.sun.com
● MQ JMS (IBM)
○ MQSeries is another messaging technology
○ Can configure MQ as a JMS provider
○ (http://www7b.software.ibm.
com/wsdd/library/techtip/0112_cox.html)
25. JMS Providers
● WebLogic JMS (BEA)
○ Enterprise-class messaging system integrated into
WebLogic Server
○ http://dev2dev.bea.com/technologies/jms/index.jsp
● JMSCourier (Codemesh)
○ Merging C++ applications into a JMS environment
○ http://www.codemesh.
com/en/AlignTechnologyCaseStudy.html
26. More JMS Vendors
● Fiorano Software http://www.fiorano.com
● JRUN Server http://www.allaire.com
● GemStone http://www.gemstone.com
● Nirvana http://www.pcbsys.com
● Oracle http://www.oracle.com
● A more exhaustive listing is available at
● http://java.sun.com/products/jms/vendors.html
