ENTERPRISEMESSAGING ANDJBOSS A-MQ

Jakub Knetl

jknetl@redhat.com

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Messaging systems

JMS specificationJMS API

JBoss A-MQ

JBoss A-MQ and Apache ActiveMQProtocolstopologies

Apache Artemis

LECTURE OUTLINE

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Method for asynchronous message (data) transfer between different systems which allowsto integrate these systems.

WHAT IS ENTERPRISE MESSAGING

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Method for asynchronous message (data) transfer between different systems which allowsto integrate these systems.

WHAT IS ENTERPRISE MESSAGING

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data exchange between applicationsMessage oriented middleware (MoM)

Message broker servers as mediator between communicating parties

ENTERPRISE MESSAGINGARCHITECTURE

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Other methods:

Webservices (REST, SOAP)JDBC and ORMRMICORBA...

WHY DO WE NEED ANOTHERCOMMUNICATION METHOD?

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BENEFITS OF MESSAGING SYSTEMAsynchronous communicationLoose couplingScalabilityReliabilityMessage routing and transformation

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Web music streaming service, which allows to upload and store your own music files. Musicfiles are stored in the ogg format in some shared storage (NAS, cloud, whatever, ...).However it allows to upload music in many formats (mp3, flac, wav, aac, and others) whichare converted by the service into ogg.

Where will we convert data?

EXAMPLE USE CASE

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Web music streaming service, which allows to upload and store your own music files. Musicfiles are stored in the ogg format in some shared storage (NAS, cloud, whatever, ...).However it allows to upload music in many formats (mp3, flac, wav, aac, and others) whichare converted by the service into ogg.

Where will we convert data?

server side?client side?

Usually none of them because of required CPU performance...

EXAMPLE USE CASE

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Benefits

asynchronous communication - server doesn't need to wait neither until data areencoded or sentloose coupling - server doesn't need to know anything about the encoderscalability - we may just start new processes as encodersmessage routing and transformation - message may be arbitrary routed betweenusing metadata information

1 server will just simply store data into temporary place shared storage

2 It will sends message containing metadata about music file into a queue

3 There may be arbitrary numbers of running consumer, which will perform encodingand upload into final storage location in ogg format.

EXAMPLE USE CASE - SOLUTION

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JMS SPECIFICATIONgoal is to:

provide messaging functionality to the java applicationsmaximizes portability between messaging productsdefine common messaging concepts

JMS provides API for messaging productsJMS is not messaging system!JMS does not address:

load balancingfault toleranceadministrationwire protocolsecurity

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BASIC TERMSJMS providerJMS client

producer/consumer

non JMS clientJMS destinantionJMS domainsJMS Message

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MESSAGE STRUCTUREHeaders

metadata about messagestored as key value pairstwo types (differs only semantically):

headers (same for all messages)properties

arbitrary key-values (some of them arestandardized)

Payload

may contain different types of payload

JMS MessageJMS Headers

JMS Properties

JMS payload

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MESSAGE HEADERS LISTHeader name meaning

JMSDestination destination on the broker

JMSDeliveryMode persistent or nonperistent delivery mode

JMSExpiration message will not be delivered after expiration

JMSMessageID Identifiaction of the message

JMSPriority Number 0 - 9 (0-4 low, 5-9 high priority). Advise only

JMSTimestamp Time when the message is handed to provider for send

JMSCorrelationID links message to another one

JMSReplyTo Destination for reply

JMSRedelivered Contains true if the message was likely redelivered

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PREDIFINED PROPERTIES

Search through JMS specification!

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MESSAGE SELECTORSMessage filtering based on properties and headersCondition based on subset of SQL92

FLIGHT_NUMBER LIKE 'N14%'

PRICE

MESSAGE CONTENTThere are several types of message defined in JMS:

TextMessage - String contentMapMessage - "body contains a set of name-value pairswhere names are Strings and values are Java primitive type"BytesMessage - stream of uninterpreted bytes bytesStreamMessage - stream of java primitive values (read and filled sequentially)ObjectMessage - Serializable object

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COMMUNICATION DOMAINSCommunication type:

Point-to-point (PTP)Publish/Subscribe (Pub/Sub)

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POINT TO POINT COMMUNICATIONDestination is a queueone of multiple consumers gets messageLoad is distributed across consumersMessage is stored until some consumers receives it

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PUBLISH SUBSCRIBE DOMAINDestination is a topicmessage is delivered to all subscribersmessage is thrown away if there is no subscriptionDurable subscriber

if durable subscriber disconnects broker is obliged to store all messages for laterdelivery

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IT IS TIME FOR HISTORY...

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JMS APIJMS 1.0 (2001)

Different APIs for pub/sub and PTP communication

JMS 1.1 (2002)

Classic API - unified API for pub/sub and PTP

JMS 2.0 (2013)

Classic API

it is not deprecated and will remain part of JMS indefinitely

Simplified API

less code neededAutoCloseable resources -> Java 7 neededno checked exceptions

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CLASSES OF CLASSIC APIConnectionFactoryConnection - heavyweight object (allocates resources outside JVM)Session - lightweight object

factory for MessageProducer, MessageConsumer and Destinationshould not be shared between threadsdefines serial order and transaction context

MessageProducer

for producing messages

MessageConsumer

for consuming messages

Destination - administered objectMessage

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RELIABILITY OF MESSAGEdelivery modeacknowledgement modetransactional mode

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DELIVERY MODEdetermines level of delivery reliability

Persistent (default)

provider should persist the messagemessage must be delivered once and only once even in case of provider failure

Nonpersistent

provider is instructed not ot presist the messagemessage must be delivered at most oncemessage is usually lost on provider failurebetter performance

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MESSAGE ACKNOWLEDGEMENTDelivery between broker and client is not considered successful until message isacknowledged.acknowledgement modes:

AUTO_ACKNOWLEDGEDUPS_OK_ACKNOWLEDGECLIENT_ACKNOWLEDGE

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TRANSACTIONSSession can be transactedmultiple messages handled as atomic unittransaction is completed by calling commit() or rollback() on sessioncommit also acknowledges messageSupport for distributed transaction is not required by JMS

but still many providers implement distributed transactionsJMS recommends support using JTA XAResource API

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CODE EXAMPLES

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PART IIAPACHE ACTIVEMQ

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APACHE ACTIVEMQOpensource MoMJMS 1.1 compliantSupports many protocols and clientsother features:

High availabilityscalibilitymanagementsecurity

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JBOSS A-MQOpen-source messaging platformMessaging system based on Apache ActiveMQRuns on OSGI containerEnable easy deploymentProvides web based management console

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JBOSS A-MQ

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CONFIGURATIONXML filemost of things work out of the box configuration example

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http://activemq.apache.org/xml-configuration.html

MESSAGE STORESkahaDBmulti kahaDBlevelDBJDBC

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CONNECTION TO BROKERTransport connectors

For client to broker connections

Network connectors

For broker to broker connections

Many transport protocols supported:

tcp, udp, nio, ssl, http/https, vm

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WIRE PROTOCOLSOpenwireSTOMPAMQPMQTT

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PROTOCOL URISdetermines what:

protocol will be usedlocation of the broker (typically hostname and port)

high level uris:

typically uses composite URIfailoverfabric

failover:(tcp://primary:61616,tcp://secondary:61616)?randomize=false

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RUNTIME MANAGEMENTThere are three options for management:

web consoleJMXKaraf OSGi console

DEMO!

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HIGH AVAILABILITY (HA)Messaging systems usually processes business critical databroker must be accessible 24/7ActiveMQ provides various mechanisms to ensure HA

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HA IN ACTIVEMQGroup of brokers forms logically one brokerMaster broker

communicates with clients

Slave brokers

Passive (all connectors are stopped)

election mechanismsclient reconnects in case of failure (failover)Message acknowledgment after the message is stored safely

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MASTER SLAVE FOR HAShared JDBC master/slaveShared file system master/slaveReplicated levelDB master/slave

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SCALABILITY: NETWORK OF BROKERSconnections between brokermessage forwardingenables massive scalabilityrequires careful configuration

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NETWORK CONNECTOR

Broker A :

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NETWORK OF BROKERSduplex connectionsdestination filteringdynamic vs static forwardingAdvisoryMessagesnetwork consumer prioritynetworkTTL

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HIERARCHIES OF NETWORKSconcentrator topologyhub and spokes topologytree topologymesh topologycomplete graph

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OTHER ACTIVEMQ FEATURESexclusive consumersmessage groupscomposite destinationswildcards (. * >)virtual destinations

See http://activemq.apache.org/features.html

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http://activemq.apache.org/features.html

APACHE ACTIVEMQ ARTEMISnew Apache MoMnon-blocking architecture => great performancemerges codebase with JBoss HornetQJMS 2.0 compliantSupport for:

ActiveMQ clientsAMQPSTOMPHornetQ clients

More details on .Artemis website

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https://activemq.apache.org/artemis/

THANK YOU!

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