JMS DEEP DIVERyan Cuprak

About Me

Ryan Cuprak• @ctjava• rcuprak@gmail.com• http://www.cuprak.info• https://www.linkedin.com/in/rcuprak

Updated For• EE 7• EJB 3.2

Agenda

Custom Features

Best Practices

Gotchas

JMS Background

• Specification Revisions• JMS 1.0.2b – June 26, 2001• JMS 1.1 – April 12, 2002• JMS 2.0 – May 21, 2013• JMS 2.1 – Vote to Continue!

• Mandatory in Java EE 1.4 (November 11, 2003)!• MOM pre-dates JMS & Java EE

JMS Ecosystem

#1 Upgrade Code to EE 7

Major changes in Java EE 7 (JMS 2.0)Introduced in Java EE 7:• JMSContext – replaces Connection and Session• JMSProducer – replaces MessageProducer• JMSConsumer – replaces MessageConsumer

Best Practice

#1 Upgrade Code to EE 7…

Best Practice

#1 Upgrade Code to EE 7…

Best Practice

#2 ActiveMQ & Java EE 7

Gotcha

#2 Java EE 7: Stumper…

What???

Gotcha

#2 Java EE 7: Stumper…

http://tinyurl.com/h7cvl8bActiveMQ supports JMS 1.1 – not JMS 2!

Gotcha

#3 Exception Handling

What is the impact of a RuntimeException?

Bad!

Best Practice

#3 Exception Handling…

Runtime Exception:• Rollback and re-delivery of message• Destruction of MDB and possibly connection

Best Practice

#4 Which of these are optional?

1. JMSMessageID2. Overriding Message Header Fields 3. JMS Defined Properties4. Provider Specific Properties5. Distributed Transactions6. Multiple Sessions

All of them!

Best Practice

#5 Pre-fetching

• Message consumer (RAR) pre-fetches a set of messages to distribute to consumers (MDBs).

• Poorly configured pre-fetch• Starve other consumers• Heap exhaustion

• Default ActiveMQ: 1000 messages!

Gotcha

#4 Pre-fetching

Consumer starved!

Gotcha

#5 Large Messages

What happens to a container when you send gigantic messages with large pre-fetch?

Best Practice

#6 XA Transactions

How do you ensure that a messages is committed only if the database commits?

Best Practice

#6 XA Transactions

XA Data Source

Best Practice

#7 Wire Protocols

What are the different wire protocols and what are their unique features?• Openwire

• Cross language wire protocol for messaging• Native protocol for ActiveMQ

• AMQP – Advanced Message Queuing Protocol• ISO 19464 – binary wire protocol with widespread adoption• Designed for high performance interoperable messaging

• MQTT – Message Queue Telemetry Transport• Simple binary protocol – good for embedded/mobile

• Stomp – Simple/Streaming Text Oriented Messaging Protocol• Text based protocol with simple semantics

Are you using the right wire protocol?Best Practice

#7 Wire Protocols & MOMMOM OpenWire AMQP MQTT Stomp Other

OpenMQ X X

ActiveMQ X X X X

RabbitMQ X X X

HornetQ X XWebLogic X

WebSphere MQ

X X

• MQTT – IoT/embedded/mobile• Stomp – WebSockets – not high volume

Best Practice

#8 Dead Letter Queue

What is the dead letter queue and why should I care?• Message that is repeatedly refused by a client.• JMS provider will retry multiple times.• Messages ultimately moved to Dead Letter Queue

(DLQ)Order Queue Update Queue Update Queue

Update QueueBest Practice

#8 Dead Letter Queue…

• Hundreds of messages• How to recover?

Best Practice

#8 Dead Letter Queue…

ActiveMQ DLQ configuration – DLQ per queue.

Best Practice

#9 Expiring Messages

What’s wrong with the following code?

1. Message.setJMXExpiration() is for use by the container.

2. Ignored if you set it.

Gotcha

#9 Expired Messages & DLQ

• Expired messages dumped to DLQ• Messages build-up over time!

Best Practice

#9 Expired Messages & DLQ…

ActiveMQ solution

HornetQ

HornetQ messages are lost unless configured.Best Practice

#10 MDB Pools

Do I need to configure MDB pools?

Best Practice

#10 MDP Pools…

• Don’t accept default MDB pool sizes.• Monitor and adjust MDB pool sizes based on load.

glassfish-ejb-jar.xml

Best Practice

#11 Types of JMS Messages

What are the different types of messages types?StreamMessage Serialized stream of objects.

MapMessage Message composed of name/value pairs. Names must be unique.

TextMessage Simple message for Strings.

ObjectMessage Message consisting of a serialized Java Object.

BytesMessage Raw stream of bytes.

WebLogic includes XMLMessage:• Optimized for XML.• Supports filtering on XML content.

Best Practice

#12 Troubleshooting

What’s this message?

?Best Practice

#12 Troubleshooting

Set descriptive headers on the messages!

Best Practice

#13 Web Socket and JMS

Java EE 7 ServerWeb Socket

EndpointJMS Provider

JMS ProviderStomp over Web Sockets

Best Practice

#13 Web Socket and JMS…

• Stomp protocol is a simple text-oriented messaging protocol.

• Messaging server must support WebSockets• Initial handshake is HTTP

• Message providers supporting STOMP & WebSockets:• ActiveMQ• RabitMQ• WebLogic

• Enable for ActiveMQ:<transportConnector name="ws" uri="ws://0.0.0.0:61614"/>

Best Practice

#14 Delayed Message Delivery

Can I send a message but have it delayed?

Extended feature in ActiveMQ.• Send delay (AMQ_SCHEDULED_DELAY)• Re-send delay (AMQ_SCHEDULED_PERIOD)• Repeat count (AMQ_SCHEDULED_REPEAT)

Best Practice

#15 Priority & Messages

What does message priority mean?• Message priority scale: 0-9 (0: lowest 9: highest)• Default message priority: 4• JMS specification does not require a provider strictly implement message ordering.• Not dependable!

Best Practice

#15 Priority & Messages

Enforcing priority:• Apache Camel with Resequencer

• http://camel.apache.org/resequencer.html

• Use Selectors:• JMSPriority > 6• JMSPriority < 6

Best Practice

#16 Protocol Framing

So I need a bigger message frame?

104 MB

Best Practice

#16 Protocol Framing

Client exception:

Server ExceptionWARN | Transport Connection to: tcp://127.0.0.1:54025 failed: java.io.IOException: Frame size of 404 bytes larger

Best Practice

#17 Leaks & Variable Loads

Load testing always at 100%?Scenario:• Message Driven Bean with a connection to a remote

resource.• Standing pool size: 3

Gotcha

#17 Leaks & Variable Loads…

Oops, resource only leak as bean instances fluctuate!

1 2 3 4 5 6 70

5

10

15

20

25

30

35

LeakBean

Gotcha

#18 Advisory Messages

Extended ActiveMQ feature:• Consumers, producers and connections starting and

stopping• Temporary destinations being created and destroyed• messages expiring on topics and queues• Brokers sending messages to destinations with no

consumers.• Connections starting and stopping

Best Practice

#18 Advisory Messages…

Best Practice

#20 Know your Activation Spec Properties

Property Required Default DescriptionacknowledgeMode Auto-acknowledge Auto-acknowledge or Dups-ok-

acknowledge

clientId Set n RA Required for durable

destinationType X null Queue or Topic

Destination X null Destination name

enableBatch false Transaction batching

maxMessagesPerBatch 10 Message per transaction batch

maxMessagesPerSessions 10 Pre-fetch size

maxSessions 10 Max concurrent sessions

messageSelector null Selector

noLocal false Include local msg?

ActiveMQ

Best Practice

#20 Know your Activation Spec Properties

Property Default Descriptionpassword Set inRA Password for JMS connection

subscriptionDurability NonDurable NonDurable or Durable

subscriptionName null Name of subscription

userName Set in RA Username for JMS connection

useRAManagedTransaction false

initialRedeliveryDelay 1000 Re-delivery delay

maximumRedeliveries 5 Max re-deliveries

redeliveryBackOffMultiplier 5 Multiplier for back-off.

redeliveryUseExponentialBackOff false Configures exponential back-off.

ActiveMQ

Best Practice

#20 Know your Activation Spec Properties

• ActiveMQ – only 2 properties were required• Key tuning questions:

• Individual messages take a long time to process?• Many messages or few messages?• Batch processing of messages?• Ok to process duplicates?

Best Practice

#21 Configuration Conflicts

Default for configuration for an MDB and ActiveMQ RA:• Max MDB Pool Size (default 25)• Max Sessions (default 10)• MaxMessagesPerSessions (default 10)

How many messages can we process concurrently?

10Best Practice

#22 Configure Message Persistence

• JMS message providers message persistence is often configurable and tunable

• Concerns:• Available file/descriptors and disk space• I/O throughput • Flush frequencies

• ActiveMQ• KahaDB – file-based transaction data store (journaled) • AMQ message store – file based store, file per destination, index

must be rebuilt for non-planned termination• JDBC message store

Best Practice

#22 Configure Message Persistence…

API does exist for ActiveMQ KahaDB!Best Practice

#23 Deadlocked Consumer

Consumer blocks!• Pre-fetched messages are stuck in limbo• App cannot be un-deployed• App container may not shutdown properlyGotcha

#24 Multiple Destinations

• ActiveMQ supports sending messages to multiple queues and topics.

• Targets should be a comma separated list.• Use prefix topic:// or queue://

Extended Feature

#25 Multiple Destination Consumption• ActiveMQ supports consuming messages from multiple destinations – both

queues and topics• Destination naming:

• ‘.’ separates elements in a destination name• ‘*’ matches one element• ‘>’ matches one or all trailing elements

• Example topics:• us.ca.sfo.takeoffs• us.ca.sfo.landings• us.ca.lax.takeoffs• us.ct.bdl.takeoffs

• Patterns:• *.*.*.takeoffs – receive all takeoff messages• us.ca.> - all landings and takeoffs in CA

Extended Feature

#25 Multiple Destination Consumption…

Extended Feature

#26 GlassFish 4 Bug

Containers can have bugs!• GlassFish 3.x no message delay with MDBs and

ActiveMQ.• GlassFish 4.1.1 2 minute delay with messages from

ActiveMQ but NOT OpenMQ

Gotcha

#26 GlassFish 4 Bug…

Timeout increased to 2 minutes!

Gotcha

#26 GlassFish 4 Bug…

Code path was different for OpenMQ.

Gotcha

#27 Transactions

SaveException thrown

Single TransactionBest Practice

#27 Transactions…

To ensure item is saved:

Best Practice

#28 Concurrency

Following objects support concurrent access:• ConnectionFactory• Connection• DestinationFollowing object DO NOT support concurrent access:• Session• MessageProducer• MessageConsumer

Best Practice

#29 JMSX PropertiesProperty Matched Modified Description

JMSXUserID X X Id of user sending messageJMSXAppID X X App sending messageJMSXProducerTXID Producer transaction idJMSXConsumerTXID Transaction ID consumerJMSXRcvTimestamp Time delivered to consumerJMSXDeliveryCount X Delivery attemptsJMSXState Provider specific stateJMSXGroupID X X Message group idJMSXGroupSeq X X Sequence number in group

No all properties are supported by all providers!

Best Practice

#30 Message Groups

• Message Groups:• Guaranteed ordering of the processing of related messages across a

single queue• Load balancing across multiple consumers.• High availability / auto-failover

• Usage:• message.setStringProperty("JMSXGroupID", ”JavaOne");• message.setIntProperty("JMSXGroupSeq”,1);• message.setIntProperty("JMSXGroupSeq”,-1); // closes group

• ActiveMQ enhancement:• JMSXGroupFirstForConsumer

Best Practice

#31 Message Selectors

• Message selectors used to filter messages.• Selectors use subset of SQL92• Selectors cannot reference payload, only header

propertiesLiterals TRUE/FALSE, numbers, scientific notation

Identifiers Header or property field.

Operators AND, OR, LIKE, BETWEEN, =, <>, <, >, <=, =>, +, -, *, /, IS NULL, IS NOT NULL

Best Practice

Best Practices

• High availability (HA) for production• Protect queues/topics with passwords• Enable and configure SSL• Configure provider data store • Backup provider data store• Configure DQL policy• Monitor DLQ• Add descriptive message headers• Pick and tune messaging transport• Use Apache Camel and integration patterns

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JMS 2.1

Vote for JMS 2.1!• Flexible MDBs (EE)• CDI beans as Listeners• Batch Delivery• Acknowledgment Modes• setMessageListener (EE)• create Connection factory (SE)• create Queue/Topic (SE)• Repeatable Annotations• Redelivery configuration (EE)

Q&A