Implementing an Esb using Mule

 Overview of ESB
 Introduction to Mule
 Mule and JBI
 Real-world Application
 Application Overview
 Systems Involved
 Design Considerations
 Event Flows
 Implementation with Mule
 Components
 Transports
 Returning the Loan Quote
 Fault Tolerance
 Scaling
 Summary

 What is it?
 Enterprise Service Bus is an evolving architecture technique
to integrate incompatible business applications over a
common messaging bus.
 Why do we need it?
 Many of the applications we write are in fact integration
projects. Only the most simple applications do not need to
interact with other applications.
 Where does SOA fit in?
 ESB is one architecture style that abides by the rules of a
Service Orientated Architecture.
 What is JBI?
 Java Business Integration (JSR:208) is an emerging standard
that defines common interfaces for components and message
exchanges for application integration.
 Does this all sound familiar?
 There is nothing new about integration, we've been doing it
for years. So why the hype?

 Loosely Coupled
 Event-Driven
 Highly Distributed
 Security/Authorization
 Abstract Endpoints
 Intelligent Routing
 Data Transformation (inbound/outbound)
 Reliable Messaging
 Multi-Protocol Message Bus
 Light Weight

 Service container and messaging platform
 Supports a variety of topologies including ESB
 Highly Scalable; uses SEDA event model
 Lightweight and embeddable
 Transactional; Local and Distributed
 Fault tolerance; Exception management
 Secure; authentication/authorization (Using
Spring/Acegi)
 Powerful event routing capabilities (based on EIP
book)
 Support for over 20 messaging protocols/transports
 End-to-End Data Transformation
 Management and Monitoring using JMX
 BPEL Support
 Deployment: JAR, WAR, RAR, EAR.

Enterprise Service Bus
Client/Server and Hub n' Spoke
Peer Network
Pipeline
Enterprise Service Network

 Is Mule a JBI container?
 There is a separate project called Mule JBI that is a JBI
implementation that reuses the Mule service stack.
 Does Mule work with JBI?
 You can use Mule transports, components and transformers inside
any JBI container. Mule provides a couple of components that
allows JBI components to subscribe and publish events to and
from Mule.
 Do Mule and JBI compete?
 JBI solves a subset of messaging problems. Mule addresses the
basic need to move any kind of data (not just XML) between
services in an organization
 Which is best for me?
 Mule of course!
 The reason Mule integrates with other JBI engines and provides it
own JBI container is that one integration solution will never
satisfy all integration needs.
 Mule levels the playing field allowing you to pick and choose
which technologies to integrate with.

 JBI
 Described in terms of Service Engines (SEs) which are akin to
components that execute business logic.
 Binding Components (BCs) implement protocols to provide
connectivity to SEs.
 JBI uses a Message Exchange to manage interactions between
components.
 Targeted a specifically at integration. Normalized Message
 Mule
 Components are POJOs, EJBs, Spring Beans, Remote objects.
 The component never needs to call Mule APIs making them
totally portable.
 Flexible endpoint model where a component may have zero or
more inbound and outbound endpoints.
 Message routing is done via routers that are associated with
the component.
 Mule is a ubiquitous messaging platform.
 A distributed container for wiring components.

 Customer calls different banks to find the best deal.
 Each bank asks customer for his or her social security number, the
amount of the loan and the desired term.
 Each bank then investigates the customer's credit background,
usually by contacting a credit agency, before it finally sends the
customer a quote.
 Once the customer has received quotes from all banks, he or she
can then select the best offer, i.e. the lowest rate. [1]

 This process can be automated to allow customers to
obtain the best quote on-line from a far broader range of
banks, in much less time than if he or she were to obtain
all the quotes one by one.
 Upon receiving customer request, Loan Broker:
 obtains the credit information for that customer from the
credit agency
 requests quotes for the customer from banks listed with the
Lender Service
 sends aggregate compilation of quotes to the customer for
selection. [2]

Loan Broker Service Receives LoanRequests (customer, SS
number, loan amount, duration) and is
responsible for aggregating LoanQuotes
into response for the request.
Credit Agency Service An external service provider that provides
crediting checking on customers to ensure
the loan amount requested is feesible.
Credit Agency Gateway Marshals a request between the message
bus and the Credit Agency Application.
Lender Service Based on the customer's credit scoring,
loan amount and duration, the lender
service will select banks from which to
request a LoanQuote.
Lender Gateway Marshals a request from the message bus
to the Lender Application.
Banking Gateway Dispatches LoanRequests to one or more
banks.

 LoanBroker (Http/Rest)
 Receives Requests over Http from a client application, such as a web
browser.
 Credit Agency (EJB)
 Is an EJB application that is managed by the Loan Broker company. It
exposes an EJB called creditAgency with a method getCreditProfile.
 Lender Application (VM)
 Is a local component, a Pojo that will determine which lenders should
be used.
 Banks (SOAP)
 For simplicity of this example all banks expose the same WS interface,
though it's quite feasible to configure Mule to invoke different
interfaces for different banks.
 Gateways (JMS)
 Gateways marshal the requests from the message bus to external
applications and services.

 Constraints
 Application needs to support request/response
processing model.
 Will get a high volume of requests.
 Synchronous processing will not give us enough
throughput.
 Transports
 Using a JMS message bus
 Need to invoke services over JMS, Http/Rest, VM, and
SOAP.
 Need to invoke services in external application
containers (EJB).
 Expose components as Web services (Banks).
 Message
 The message on the bus is referred to as a

1. Client application makes a request sending the LoanBroker a
CustomerQuoteRequest Message.
2. LoanBroker creates a LoanQuoteRequest Message.
3. Mule sends the message to the Credit Agency Gateway via JMS
4. The Gateway marshals the request and invokes the
CreditAgency EJB. The component used in the
RelectionMessageBuilder which automatically attaches the
CreditProfile to the LoanQuoteRequest message.
5. Mule sends the Message to the Lender Gateway via JMS
6. The Gateway uses the VM transport to invoke the Lender
Application.
7. Mule sends the Message to the Banking Gateway via JMS
8. The Banking Gateway in this example invokes the Banks using
SOAP.
9. Each of the Banks attaches a quote to the request and sends
it back to the LoanBroker via the ReplyTo address provided by
the Banking Gateway.
10.The ResponseRouter on the Loan Broker Service receives the
responses on the ReplyTo address. It selects the lowest quote
received for the request and returns it to the client.

Lets start by defining the LoanQuoteRequest Message. In this example the
Message is a Java bean and is the common message format on the bus.
Normally this would be XML, but Mule allows us to pass any data format around.
public class LoanQuoteRequest implements Serializable
{
/** The request contains Customer info and loan amount and duration*/
private CustomerQuoteRequest customerRequest;
/** credit profile for the customer */
private CreditProfile creditProfile;
/** A list of lenders for this request */
private Bank[] lenders;
/** A loan quote from a bank */
private LoanQuote loanQuote;
.......
}

 The whole chain of events is initiated with a client
request. This is done over Http using Mule's REST support.
It is described in the Endpoint address –
jetty:rest://localhost:8080/loanbroker
 Here we're saying -
 Embed a Jetty Servlet Engine
 Use the Rest servlet for receiving requests
 Listen on localhost:8080
 Bind the Rest servlet to the context /loanbroker
 The request from the client would look like –
http://localhost:8080/loanbroker/?
name=Ross+Mason&ssn=1234&
loanAmount=10000&loanDuration=24

 The Loan Broker endpoint receives the request as a set of Http parameters,
but we need to transform this into a CustomerQuoteRequest object before
the Loan Broker component receives it.
 We do this by configuring a custom transformer on the endpoint.
public Object transform(Object src, UMOEventContext context)
throws TransformerException {
String name = context.getStringProperty("name");
int ssn = context.getIntProperty("ssn");
double amount = context.getDoubleProperty("loanAmount");
double duration = context.getDoubleProperty("loanDuration");
Customer customer = new Customer(name, ssn);
CustomerQuoteRequest request =
new CustomerQuoteRequest(customer, amount, duration);
return request;
}

 The Loanbroker service actually doesn't need to do anything but trigger the
LoanQuoteRequest on the bus. Mule handles all routing transformation and passing the
quote back to the callee.
 The transformer configured on the REST inbound endpoint for the LoanBroker converts
the REST parameters into a CustomerQuoteRequest object.
public class LoanBroker
{
public LoanQuoteRequest requestLoanQuote(
CustomerQuoteRequest request) throws Exception
{
LoanQuoteRequest bqr = new LoanQuoteRequest();
bqr.setCustomerRequest(request);
return bqr;
}
}

All the detail is in the Loan Broker configuration.
<mule-descriptor name="LoanBroker"
implementation="org.mule.samples.loanbroker.esb.LoanBroker">
<inbound-router>
<endpoint address="jetty:rest://localhost:8080/loanbroker"/>
</inbound-router>
<outbound-router>
<router className="org.mule.routing.outbound.OutboundPassThroughRouter">
<endpoint address="jms://esb.credit.agency"/>
</router>
</outbound-router>
<response-router timeout="10000">
<endpoint address="jms://esb.loan.quotes"/>
<router className="
org.mule.samples.loanbroker.esb.routers.BankQuotesResponseAggregator"/>
</response-router>
</mule-descriptor>

 The Credit Agency code is even easier! We use a
standard Mule Component called a
ReflectionMessageBuilder which builds a message
based on a set of results from endpoint
invocations.
 It will use reflection to determine how to set the
result of the last endpoint invocation as a
property on the master message.
 There are other MessageBuilder components such
as the ScriptMessageBuilder component which is
a JSR-223 (Scripting) component that allows you
to manipulate the payload after each request
using Groovy, JavaScript, Rhino or any other

<mule-descriptor name="CreditAgencyGateway"
implementation="org.mule.components.builder.ReflectionMessageBuilder">
<inbound-router>
<endpoint address="jms://credit.agency"/>
</inbound-router>
<outbound-router>
<router className="org.mule.routing.outbound.FilteringRouter">
<endpoint address="ejb://localhost:1099/local/CreditAgency?method=getCreditProfile“
transformers=“LoanQuoteRequestToCreditProfileArgs”
responseTransformers="CreditProfileXmlToCreditProfile“/>
<properties>
<list name="methodArgumentTypes">
<entry value="java.lang.String"/>
<entry value="java.lang.String"/>
</list>
</properties>
</endpoint>
<endpoint address="jms://esb.lender.service"/>
</router>
</outbound-router>
</mule-descriptor>

 We invoke the CreditAgency application using an EJB
endpoint –
ejb://localhost:1099/local/CreditAgency?method=getCreditProfile
 This endpoint tells Mule to –
 Look up an EJB object at localhost:1099
 Use the JNDI name local/CreditAgency
 Invoke the method getCreditProfile on the EJB object
 Notice also the transformers and responseTransformers
attibutes on the endpoint. These tell Mule how to marshal
for the Application.
 LoanQuoteRequestToCreditProfileArgs – Extracts the method
arguments from the request as an array used to invoke
getCreditProfile.

 Lender Service
 The Lender Agency is a Mule component, that receives
events directly using the VM transport.
 Leander Gateway
 The Lender Gateway marshals requests from the bus to
the lender service.

Lender Service
<mule-descriptor name="LenderService" implementation="org.mule.samples.loanbroker.esb.LenderService">
<inbound-router>
<endpoint address="vm://lender.service"/>
</inbound-router>
</mule-descriptor>
Lender Gatway
<mule-descriptor name="LenderGateway”
implementation="org.mule.components.simple.BridgeComponent">
<inbound-router>
<endpoint address="jms://esb.lender.service"/>
</inbound-router>
<outbound-router>
<router className="org.mule.routing.outbound.ChainingRouter">
<endpoint address="vm://lender.service"/>
<endpoint address="jms://esb.banks"/>
</router>
</outbound-router>
</mule-descriptor>

 The Banking Gateway is responsible for distributing requests to a list of lenders.
 The ReciptientList router configured on this gateway is responsible for extracting the
endpoints from the message and invoking them. The RecipientList is a type of Itinerary-
based router that extracts its itinerary as a static list from the event.
<mule-descriptor name="BankingGateway"
implementation="org.mule.components.simple.BridgeComponent">
<inbound-router>
<endpoint address="jms://esb.banks"/>
</inbound-router>
<outbound-router>
<router className="org.mule.routing.outbound.StaticRecipientList">
<reply-to address="jms://esb.loan.quotes"/>
</router>
</outbound-router>
</mule-descriptor>

 The banks in this example are just simple beans that
return a fixed interest rate and are exposed as SOAP
services.
<mule-descriptor name="Bank1"
inboundEndpoint="axis:http://localhost:10001/services"
implementation="org.mule.samples.loanbroker.Bank">
</mule-descriptor>
• Note to expose a component as an Axis service all you
need to do is add an Axis endpoint!

 Once a back has a quote it passes it to Mule which will send the
Quote on the reply-to endpoint specified by the Banking Gateway.
 Looking back at the LoanBroker configuration, there is a response-
router configured as -
<response-router timeout="10000">
<endpoint address="jms://esb.loan.quotes"/>
<router className="org.mule.samples.loanbroker.esb.routers.
BankQuotesResponseAggregator"/>
</response-router>
• The BankQuoteResponseAggregator is responsible for picking the
lowest quote. But before that happens Mule needs to make sure all
responses are received for the request.
• This is done using message correlation managed by Mule.

 When a event is dispatched from the Banking Gateway a
correlationId and correlationGroupSize is attached to the
SOAP message. This is a function of the Recipient List
router. It attaches the following information -
 CorrelationId – and Id that associates all the dispatched
events to the same group
 CorrelationGroupSize – how many events are in the group.
 CorrelationSequence – the order in which the events were
dispatched.
 The Response Router reads these correlation headers when
events are received and correlates the events.
 When the event group correlation is complete the
response-router invokes itself where developers can plug
in custom logic.

 The BankQuoteResponseAggregator implements a single method that
works out the lowest quote before passing it back to Mule to route
the response back to the client.
protected UMOMessage aggregateEvents(EventGroup events) throws RoutingException {
. . . .
List list = events.getEvents();
for (Iterator iterator = list.iterator(); iterator.hasNext();) {
event = (UMOEvent) iterator.next();
quote = (LoanQuote)event.getTransformedMessage();
logger.info("Processing quote: " + quote);
if (lowestQuote == null) {
lowestQuote = quote;
} else if (quote.getInterestRate() < lowestQuote.getInterestRate()) {
lowestQuote = quote;
}
}
return new MuleMessage(lowestQuote, event.getProperties());
}

 Most Mule transports can be configured
using just the endpoint address. i.e.
tcp://localhost:45454 contains all the
information necessary to make a TCP
connection.
 However for JMS and EJB we need to
define configuration properties for each
such as Jndi information.
 This is done by configuring connectors in
our MuleXml.

EJB Connector (OpenEJB – Local Server. See http://openejb.org)
<connector name="ejbConnector" className="org.mule.providers.ejb.EjbConnector">
<properties>
<property name="jndiInitialFactory" value="org.openejb.client.LocalInitialContextFactory"/>
<property name="securityPolicy" value="security.policy"/>
<map name="jndiProviderProperties">
<property name="openejb.base" value="."/>
<property name="openejb.configuration" value="../conf/openejb.conf"/>
</map>
</properties>
</connector>
JMS Connector (ActiveMQ)
<connector name="jmsConnector" className="org.mule.providers.jms.JmsConnector">
<properties>
<property name="connectionFactoryJndiName" value="ConnectionFactory"/>
<property name="jndiInitialFactory"
value="org.activemq.jndi.ActiveMQInitialContextFactory"/>
<property name="specification" value="1.1"/>
</properties>
</connector>

 Exception Strategies
 Can be defined on components and connectors
 Can be defined globally of for each connector or
component
 Can handle different exception types differently.
 Exception hierarchy provides all available information
 Event payloads can be re-routed on exception
 Connection Strategies
 Control how connectors connect to underlying resources
 Allow for flexible retry policies
 Notifications of failed connections
 Consistent endpoint state maintained
 Can alter routing paths based on failed connections

 SEDA Model
 Mule is SEDA-based, which is an architecture designed for high
concurrency and throughput.
 JMS Clustering
 Currently Mule can use JMS clustering to distribute events to a cluster of
Mule Nodes.
 Application Server Clustering
 Mule can be embedded inside a JCA container and allow the App server
to manage its resources and cluster instances.
 New Clustering Support
 The next release of Mule will provide clustering and distribution using
JGroups/JBossCache.
 Load Balancing using Mule
 You can use a Mule instance to provide load-balancing over any
transport.

 An ESB integrating a client application
and 3 back office systems.
 Combined a number of transports
including HTTP, JMS, EJB and Web
Services.
 Easy to add in Exception handling,
transactions, etc. All done through
configuration.
 All event routing, management,
transformation is handled by Mule.
 Very little code to write. Just domain-
specific logic.
 A fully functional ESB in about an hour!

 Project was founded in 2003.
 It was started after experiences with a large
Financial ESB project.
 There are now 10 developers who help support it
and add new features.
 Has an active user community.
 Is being used in companies such as HP, Sony,
Deutche Bank and CitiBank.
 SymphonySoft has been started by Mule
developers to help support and provide
professional services to these projects.
 For more information go to -
http://mule.codehaus.org.

 EIP Book (Loan Broker Example) [1][2]
 http://www.eaipatterns.com/ComposedMessagingExam
ple.html
 http://www.eaipatterns.com/index.html
 Introduction to ESBs – Rick Robinson
 http://www-
106.ibm.com/developerworks/xml/library/ws-esbscen/
 ESB Learning Guide
 http://searchwebservices.techtarget.com/general/1,29
5582,sid26_gci1085711,00.html
 Introduction to SEDA – Matt Welsh
 http://www.eecs.harvard.edu/~mdw/papers/mdw-
phdthesis.pdf
 Mule User Guide
 http://mule.codehaus.org/User+Guide

 To get this Loan Broker ESB code and these
slides go to -
 http://mule.codehaus.org/LoanBroker
 There are other examples too -
 http://mule.codehaus.org/Examples

Implementing an Esb using Mule

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