PEtALS ESB Architecture

Architecture
document

Petals ESB explained

The Open Source Entreprise Service Bus solution for Service Oriented Architectures

Version history
Version Date Comments, Changes, Status Authors, Contributors,
Reviewers

1.0 2009-01-11 Christophe HAMERLING –
eBM WebSourcing

Table of Contents
Introduction to Services, Web Services and SOA ................................................................ 7
Service ................................................................................................................................................................................... 7
Web Service ......................................................................................................................................................................... 7
Service Oriented Architecture ..................................................................................................................................... 7
Definition ................................................................................................................................................................................... 7
Infrastructure .......................................................................................................................................................................... 8
The Entreprise Service Bus ........................................................................................................................................... 9
Definition ................................................................................................................................................................................... 9
Architecture............................................................................................................................................................................10
Calling a service ....................................................................................................................................................................11
PEtALS Enterprise Service Bus ......................................................................................... 12
Java Business Integration ............................................................................................................................................ 13
Environment...........................................................................................................................................................................13
JBI Artifacts.............................................................................................................................................................................14
Messages ..................................................................................................................................................................................14
Delivery channel ...................................................................................................................................................................15
PEtALS High Level Architecture................................................................................................................................ 16
Software components ........................................................................................................................................................16
PEtALS Components ...........................................................................................................................................................18
PEtALS JBI Implementation ........................................................................................................................................ 19
The PEtALS JBI Container ................................................................................................................................................20
Using a JBI Component ......................................................................................................................................................20
Using a JBI Service Unit .....................................................................................................................................................21
Using a JBI Service Assembly ..........................................................................................................................................22
Using a JBI Shared Library ..............................................................................................................................................22
Using the JBI environment ...............................................................................................................................................23
PEtALS JBI Extensions................................................................................................................................................... 23
Distributed Environment..................................................................................................................................................23
Technical Registry ...............................................................................................................................................................24
Inter nodes communication ............................................................................................................................................25
Management ..........................................................................................................................................................................26
Monitoring ..............................................................................................................................................................................26
Kernel Features................................................................................................................................................................ 28
Domains....................................................................................................................................................................................28
JBI exchange optimisation ...............................................................................................................................................29
Address Resolver ..................................................................................................................................................................29
Router Module .......................................................................................................................................................................30
Transport layer .....................................................................................................................................................................30
Security .....................................................................................................................................................................................31
Hot Deployment ....................................................................................................................................................................31
Data compression ................................................................................................................................................................31
Source code........................................................................................................................................................................ 32
Modules.....................................................................................................................................................................................32
Distributions ..................................................................................................................................................................... 33
Platform ...................................................................................................................................................................................35
Standalone ..............................................................................................................................................................................35
Quickstart ................................................................................................................................................................................35
PEtALS JBI Components ............................................................................................................................................... 35
PEtALS Tools ..................................................................................................................................................................... 37
PEtALS WebConsole............................................................................................................................................................37
Eclipse Plugins.......................................................................................................................................................................39

Annexe A – Fractal Architecture ...................................................................................... 41

Figures
FIGURE 1 - SOA INFRASTRUCTURE ................................................................................................................................................ 8
FIGURE 2 - SOA ARCHITECTURE .................................................................................................................................................... 10
FIGURE 3 - CALLING A SERVICE ..................................................................................................................................................... 11
FIGURE 4 - JBI ARCHITECTURE....................................................................................................................................................... 13
FIGURE 5 - PETALS HIGH-LEVEL ARCHITECTURE ................................................................................................................ 16
FIGURE 6 - PETALS CONTAINER .................................................................................................................................................... 20
FIGURE 7 - PETALS CONTAINER AND JBI COMPONENTS .................................................................................................. 21
FIGURE 8 - PETALS CONTAINER AND JBI ENDPOINTS........................................................................................................ 22
FIGURE 9 - USING PETALS ................................................................................................................................................................. 23
FIGURE 10 - DISTRIBUTED SERVICE BUS .................................................................................................................................. 24
FIGURE 11 - INTER NODES COMMUNICATION ....................................................................................................................... 25
FIGURE 12 - GLOBAL MONITORING VISION ............................................................................................................................. 27
FIGURE 13 - MESSAGE MONITORING .......................................................................................................................................... 28
FIGURE 14 - PETALS DOMAINS ....................................................................................................................................................... 29
FIGURE 15 - WEBCONSOLE MONITORING ................................................................................................................................ 37
FIGURE 16 - WEBCONSOLE EMBEDDED CLIENT ................................................................................................................... 38
FIGURE 17 - WEBCONSOLE ARCHITECTURE ........................................................................................................................... 39
FIGURE 18 - CREATE A SERVICE UNIT WITH ECLIPSE PLUGIN ...................................................................................... 40
FIGURE 19 - JBI MESSAGING COMPOSITE .................................................................................................................................. 41
FIGURE 20 - JBI MANAGEMENT COMPOSITE ........................................................................................................................... 41
FIGURE 21 - COMMUNICATION COMPOSITE............................................................................................................................ 42
FIGURE 22 - PLATFORM COMPOSITE .......................................................................................................................................... 42
FIGURE 23 - TRANSPORTER COMPOSITE .................................................................................................................................. 43

Acronyms
Please find below the acronyms used in this document and their definition.

Acronym Definition

API Application Programming Interface

BC Binding Component

CBD Component Based Development

EDA Event Driven Architecture

ESB Entreprise Service Bus

JBI Java Business Integration

JCP Java Community Process

JMS Java Messaging Service

JNDI Java Naming and Directory interface

JSR Java Specification Request

LDAP Lightweight Directory Access Protocol

NMR Normalized Message Router

SA Service Assembly

SE Service Engine

SL Shared library

SLA Service Level Agreement

SOA Service Oriented Architecture

SOAP Simple Object Access Protocol

SPI Service Provider Interface

SU Service Unit

WS Web Service

WSDL Web Service Description Language

WSDM Web Service Distributed Management

Introduction to Services, Web Services and SOA
Service
OASIS (Advancing Open Standard for the Information Society http://www.oasis-
open.org) defines a service as a mechanism to enable access to one or more capabilities,
where the access is provided using a prescribed interface and is exercised consistent
with constraints and policies as specified by the service description. A service is
provided by an entity (the service provider) for use by others, but the eventual
consumers of the service may not be known to the service provider and may
demonstrate uses of the service beyond the scope originally conceived by the provider.

A service is accessed by means of a service interface, where the interface comprises the
specifics of how to access the underlying capabilities. There are no constraints on what
constitutes the underlying capability or how access is implemented by the service
provider.

Thus, the service could carry out its described functionality through one or more and/or
manual processes that themselves could invoke other available services.

Web Service
The current Web is mainly a collection of information but does not yet provide support
in processing this information, i.e., in using the computer as a computational device.
Recent efforts around UDDI, WSDL, and SOAP lift the Web to a new level.

Software applications can now be accessed and executed via the Web based on the idea
of Web Services. Web Services significantly increase the Web architecture's potential, by
providing a way to automate the communication between distributed applications and
the discovery or execution of remote services.

Web Services connect computers and devices using the Internet to exchange data and to
combine data and processes in new ways. Web Services can be completely decentralized
and distributed over the Internet and accessed by a wide variety of communication
devices.

Note: More about services can be found in the Reference Model for Service Oriented
Architecture OASIS Standard (http://www.oasis-
open.org/committees/tc_home.php?wg_abbrev=soa-rm).

Service Oriented Architecture

Definition
Service Oriented Architecture (SOA) is a computer system's architectural style for
creating and using business processes, packaged as services, throughout their lifecycle.
SOA also defines and provisions the IT infrastructure to allow different applications to
exchange data and participate in business processes. These functions are loosely
coupled with the operating systems and programming languages underlying the
applications. SOA separates functions into distinct units (services), which can be
distributed over a network and can be combined and reused to create business
applications. These services communicate with each other by passing data from one
service to another, or by coordinating an activity between two or more services. SOA
concepts are often seen as built upon, and evolving from older concepts of distributed

computing and modular programming.

The following guiding principles define the ground rules for development, maintenance,
and usage of the SOA:

- Reusability, granularity, modularity, composability, componentization and
interoperability

- Compliance to standards (both common and industry-specific)

- Services identification and categorization, provisioning and delivery, monitoring
and tracking

Infrastructure
A vision of the standard SOA infrastructure is given is the following figure:

Figure 1 - SOA Infrastructure

This infrastructure is composed of the following modules:

- A message delivery bus, also named the Entreprise Service Bus (ESB)

- A service orchestration engine (BAM - Business Process Management)

- A service container (such as SCA – Service Component Architecture)

- Monitoring Tools (BAM – Business Activity Management, SAM – Service Activity
Monitoring)

- Management Tools

- …

The Entreprise Service Bus

Definition
The key item for integration of services within an SOA is the ESB. The goal of an ESB is to
provide virtualization of the enterprise resources, allowing the business logic of the
enterprise to be developed and managed independently of the infrastructure, network,
and provision of those business services.

An ESB must provide a standard and flexible access to the services to the application
developer. The service consumer must be as independant as possible from:

- The communication protocol between service consumer and provider. The
service consumer must be able to access to the service via HTTP but also via FTP,
JMS, JCA, SMTP, RMI, etc…
- The service deployment technology. A Web Service, .NET component, an EJB or a
simple Java class may be accessed by the service consumer in the same way.

- The service localisation.

The ESB may also allow the service developer to deploy its services whatever the
technology or the protocol he chose to develop the service.

Ideally, the bus must:

- Support the Web Service Description Language – WSDL (WSDL 1.1
http://www.w3.org/TR/wsdl and WSDL 2.0 http://www.w3.org/TR/wsdl20/)
as the universal service description language. This is true even if the service is
not a Web Service (an EJB for example).
- Interact with clients and services through heterogenous protocols:

o Not WS-* based (e.g. HTTP, JMS, .NET, …)

o WS-* based (e.g. SOAP, WS-RM, WS-Adressing, …)

- Provide several modes to call services (synchrone, asynchrone, …)

- Trace the service calls

- Secure message exchanges

- Host local services (SCA)

- Provide management facilities

- …

Most of the ESB are based on a asynchronous messages approach. It means that,
whatever the protocol used from the consumer to the ESB and from the ESB to the

service, the ESB internally transform these calls to messages. Next, it insures the routing
and transmission of the message to the service in a transparent way from the service
consumer and the service provider. The routin gis generally based on the message
header (cf WS-Adressing), but a more advanced routing can be based on the message
content (message payload). Furthermore, the routing phase can be done with or without
acknowledgement, with or without delivery waranty, …

Architecture
The following figure introduces the functional modules that are needed to satisfy the
previous objectives.

Figure 2 - SOA Architecture

- The message transporter insures the transmission and the message security
between the various servers/hosts which are taking part in the consumers and
providers deployments.

- The protocol mediators (Service Access) are used by the ESB to support various
communication protocols between itself and the service consumers and
providers.

- The routing engine insures the messages to be routed to the good recipient based
on rules.

- The transformation engine insures the syntaxic message conversion between two
protocols. It can also provide a semantic message conversion between the

consumer and the provider.

Calling a service
The following figure illustrates the difference between a simple service call and a service
call through the ESB:

Figure 3 - Calling a Service

The client call is outed from what can be called a virtual service to the real service
through the ESB following these steps (example between parenthesis):

1. A message is sent by the client to a virtual service. This service is linked to the
ESB container by an adapter (ex: A JMS client posts a JMS message to a Topic, the
new message is detected by a listener).

2. The adapter transforms the incoming message to an ESB internal message and
sends this message to the routing engine (ex: The JMS message is transformed to
the internal ESB format).

3. The routing engine selects the ESB service to call (ex: This can be based on the
message content or by rules defined at configuration time).
4. The internal message transporter transports the message (with or without
security, hopefully with security…) to the right application server node (ex: if the
ESB is distributed over several nodes, the transport layer is in charge of sending
the message to the wire).

5. Once received by the transporter, the message is going through the router and
transmitted to the right adapter which is linked to the real service.

6. The message is transformed to the output format by the adapter (ex: The internal
message is transformed to a SOAP message).

7. The adapter sends the message to the service (ex: the SOAP message is sent to a
Web Service).

8. If the real service returns a response, this response is sent back to the service
client through the ESB…

The main question is why do we need to add an ESB as mediator instead of calling the
service directly? Here are some good reasons (this is not an exhaustive list):

- The client application does not have to wait the service response.

- The call can be securized by the ESB without any modification on the service side.

- The consumer delegates the service choice to the ESB. This really decouples the
service consumers and providers.

- Decoupling service can hide the real service which will be called to the external
service consumer. This contributes to securing access to the information system.
- The ESB offers features like monitoring (and more) which are not provided by
simple solutions like standard Web Service calls.

- Service Level Agreement (SLA) can be defined between client and service. SLA is
a part of a service contract where the level of service is formally defined (for
example, limit the number of request per second or define the maximum
response time which is accepted on the user point of view).

PEtALS Enterprise Service Bus
PEtALS (http://petals.ow2.org) is an Open Source (LGPL License) Enterprise Service
Bus (ESB) provided by the OW2 middleware consortium (http://www.ow2.org).

PEtALS ESB is build with and on top of agile technologies such as:

− The Java Business Integration (JBI) v1.0 specification
(http://www.jcp.org/en/jsr/detail?id=208). This is the Java standard for enterprise
application integration. Note that in 2008, PEtALS has been certified by SUN
Microsystems as a valid JBI implementation.
− The FRACTAL Software Component Framework provided by the OW2 consortium.
Fractal is a modular and extensible component model that can be used with various
programming languages to design, implement, deploy and reconfigure various
systems and applications, from operating systems to middleware platforms and to
graphical user interfaces.
On the PEtALS point of view, all the container services (such as service registry,
message router, message transporter, discovery etc...) are provided by the Fractal
framework. This is a major feature which allows core developers to specialize a

PEtALS distribution by choosing the software components to be used for specific
needs.
PEtALS is not only a JBI container, the project also contains tools for management,
monitoring, frawework to create JBI components to hide the JBI complexity and a
collection of Binding Components and Service Engines. All of this will be detailed in the
next chapters.

Java Business Integration
The following section introduces the high level concepts of the specification which will
be used next in the PEtALS related parts. For more advanced details, please refer to the
specification.

The JBI specification has been standardized by the Java Community Process (JCP) expert
group in the JSR208 document.

The specification defines a standard means for assembling integration components to
create integration solutions that enable a SOA in an enterprise information system.

Environment
Components are plugged into a JBI environment and can provide or consume services
through it in a loosely coupled way. The JBI environment then routes the exchanges
between those components and offers a set of technical services. JBI is built on top of
state-of-the-art SOA standards: service definitions are described in WSDL format and
components exchange XML messages in a document-oriented-model way.

Figure 4 - JBI Architecture

The central part of the JBI specification is the Normalized Message Router (NMR),
described as the “JBI Environment” in figure above. The NMR ensures loosely coupled
communication by providing standard Service Provider Interfaces (SPI) that promote
the exchange of XML documents between plugged JBI components and loose references

via the use of their interface name.

JBI Artifacts
The JBI specification defines a set of artifacts which are used to add connectivity,
bind/expose services and configure the Service Bus.

The main artefacts are the JBI components which are divided in two families:

- Binding Components (BC) – “connectors” which are used to interface the JBI bus
with the rest of the Information System (Green boxes in figure above). Binding
Components enable both the exposure of external resources in the bus and the
exposure of services available on the bus for their use by external consumers: e.g.
connections to Web services, FTP, Mail, Message-Oriented Middleware, or even
standard business communications like EDI or ebXML.

- Service Engines (SE) provide the integration logic (Blue boxes in the figure
above). They typically handle messages that pass through the bus in order to
provide routing (e.g. content-based routing, priority-based routing),
transformation (XSLT), orchestration (BPEL), log or audit features.

In order to activate endpoints in the JBI environment, artifacts named Service Units
(SU) must be deployed on the JBI component (both BC and SE). The SU contains
configuration file which are used by the JBI component consume or provide a JBI
service. A SU has two modes:

- Consumer: The component on which the SU is deployed on will consume the
service described in the SU configuration file.

- Provider: The component on which the SU is deployed on will provide the service
described in the SU configuration file.

Service Units are packaged in artifacts named Service Assembly (SA). The SA can
contain a collection of SU plus a configuration file which describe on which component
each SU must be deployed.

The last artefact defined in the JBI specification is the Shared Library (SL). The SL is an
artefact which can be shared between JBI components. The components will potentially
use the Java libraries and resources bundled in the SL to create their class loaders.
In this document, a JBI artefact will refer to the previously detailed items. More details
on Binding Components, Service Engines, Service Units, Service Assemblies, Shared
Libraries, their lifecycles and usage are described in the JBI specification.

Messages
The atomic JBI message, also called Normalized Message, is composed of a XML payload,
attachments (binary data) and key-value properties (also view as message context). A
JBI message transits between service consumer and provider in a Message Exchange. A
Message Exchange contains an input Normalized Message, a set of key-value properties
and potentially:

- An output Normalized Message representing the service invocation response.
This depends on the Message Exchange Pattern (MEP) used to invoke the service.

- A Fault (extension of a Normalized Message) when something wrong occurs on
the service side.

- A Pattern

- A Status

- …

The Message Exchanges can be classified by patterns (inspired by the WSDL 2.0
specification); we talk about Message Exchange Pattern (MEP):

- InOnly: This pattern is used for one-way exchanges

o The service consumer sends a message

o The service provider replies by an aknowledge

- InOut: This pattern is used for two-way exchanges.


o The service provider reploies by a message or a fault

o The service consumer acknowleges

- InOptionalOut: This pattern is used for a two-way exchange where the provider's
response is optional


o The service provider can send back a response, a fault or just an
acknowledgement. The consumer:

Acknowledges the response

Or sends a fault, in this case the provider must acknowledge this
fault

Or acknowledges the initial fault

- RobustInOnly: This pattern is used for reliable, one-way message exchanges


o The service provider acknowledges or send back a fault

o If a fault is returned, the service consumer acknowledges

More details on section 5.4.2 of the JBI specification.

Delivery channel
The Delivery Channel (DC) is the interface between the components and the Normalized
Message Router:

- The consumer (a JBI component) sets the message exchange (payload,

attachments and properties) and send the message to the delivery channel

- The message bus is in charge of transmiting the message to the component which
is providing the requested service

- The provider (a JBI component) receives the message exchange from its delivery
channel and processes the message. Depending on the message pattern, a
response, fault or acknowledgement can be set in the message exchange. The
message exchange is then sent back to the consumer through the delivery
channel.

PEtALS High Level Architecture
The PEtALS architecture has been defined using the software component paradigm. The
following figure introduces the main components which are required to build the
PEtALS container.

Figure 5 - PEtALS High-Level Architecture

Details about the software components are detailed in the next section.

Software components
The container kernel is build upon the software component paradigm. The Component
Based Development (CBD) emphasises on decomposition of the engineered systems into
functional or logical components with well-defined interfaces used for communication
across the components. Components are considered to be a higher level of abstraction
than objects and as such they do not share state and communicate by exchanging

messages carrying data.

By assembling components implementations, it is possible to specialize a software for
different needs. In the PEtALS container context, we can easily replace a complex
distributed registry by a local hastable and provide a simple standalone PEtALS
distribution (plus some distributed components). This is one of the interesting features
the software component model provides.

One other powerful feature will be the possibility to replace software components at
runtime. Even if this approach will never be used in production environment, let’s
imagine that you need to replace the JMS based communication channel by a HTTP one
because your network topology or firewall settings have changed. This will be possible
without stopping the container. Just stop the component (all the calls to this component
are buffered during the operation), undeploy it then deploy and start the new
component which provide the same interface. There is no impact on the container and
all the buffered messages are then send to the new component!

On the PEtALS developer point of view, working with Fractal components is like
working with Java interfaces, annotations and descritpor files.
@FractalComponent
@Provides(interfaces = @Interface(name = "service",
signature = org.ow2.petals.jbi.management.installation.InstallationServiceMBean.class))

public class InstallationServiceImpl implements InstallationServiceMBean {

@Requires(name = "configuration",
signature = org.ow2.petals.kernel.configuration.ConfigurationService.class)
private ConfigurationService configurationService;

…

}

This code snippets taken from the PEtALS kernel sources specifies that :

- The InstallationServiceImpl is a Fractal component (FractalComponent
annotation).

- The Fractal component provides a service to other components which is defined
by the InstallationServiceMbean interface (Provides annotation) and which is
implemented in the current class.

- The InstallationServiceImpl need to use a service which provides the
ConfigurationService interface.

Since the Fractal component implementation provides and requires services
implementation, all the component implementations are binded together using XML
descriptor files. This descriptor file is processed at compile time is used to generate the
final Java byte code.

The OW2 Fractal component model has been chosen for its very structuring architecture
and is used in the PEtALS container to separate and identify modules. Fractal is not
limited to the features introduced above. The framework is really powerful; we really
encourage users and developers to have a look to the documentation which can be found
on the Fractal Web Site (http://fractal.ow2.org).

PEtALS Components
As described in the previous section, PEtALS is built using the software component
approach. The main PEtALS components are listed below:

- The Container Service (org.ow2.petals.container.ContainerService interface) is
the main container component. Its role is to create the JBI artefacts lifecycles,
installers. In the kernel point of view, the resources created by this service are
wrapped into Fractal components.

- The Router (org.ow2.petals.jbi.messaging.routing.Router interface) acts as the
central part of the JBI container. The router is in charge of choosing the right
endpoint to send the JBI message to.

- The Transporter (org.ow2.petals.transport.Transporter interface) is the mediator
between the router and the communication channel. Its roles are:

- Sending messages to the endpoint resolved by the NMR. As explained in
the inter node communication section, sending a message to an endpoint
can be just an in memory process or if the endpoint is located on a foreign
container, the message is serialized into the wire format then send to the
foreign container.

- Receiving messages which is exactly the opposite of the sending role.

- The Endpoint Registry (org.ow2.petals.jbi.messaging.registry.EndpointRegistry
interface) is in charge of storing the endpoint references and their service
descriptions (WSDL descriptions). The endpoints are classified in a tree form
(interface, service and endpoint branches) in order to optimize their retrieval.

- The Network Service (org.ow2.petals.communication.network.NetworkService
interface) is responsible of managing nodes whi want to join or leave the PEtALS
network. NOTE: This service must handle the state of the remote nodes by sending
hello/ping messages…

- The Topology Service (org.ow2.petals.communication.topology.TopologyService
interface) holds all the PEtALS nodes configuration. The complete topology
information of the PEtALS network is updated when nodes are joining or leaving
the network.

- The Configuration Service
(org.ow2.petals.kernel.configuration.ConfigurationService interface) handles the
configuration of the local PEtALS container. This local configuration (class
org.ow2.petals.kernel.configuration.ContainerConfiguration) contains data for
the container such as topology, server properties (name, timeouts, QoS, JAAS,
SSL…) but also domain and subdomain informations.

- The Repository Service (org.ow2.petals.platform.repository.RepositoryService
interface) handles JBI artefacts resources needed at runtime by the container.
When a JBI artefact is installed/deployed on the container, it is exploded in a
distinct folder holded by the Repository Service.When the container is restarted,
all the JBI resources are reloaded from their repository path. This allows JBI
artefacts such as components to store/persist resources to be reused in their

dedicated workspace.

- The System State Service
(org.ow2.petals.platform.systemstate.SystemStateService interface) is in charge of
storing states (lifecycle state, installation URL, source URL, …) and maintening
the consistency whenever a JBI artefact state is updated. The system state and the
repository services work together to reload resources on container reload.

- The JMX Service (org.ow2.petals.communication.jmx.JMXService interface) is used
to manage JMX connections to a local or a remote PEtALS container. The JBI
specification defines a set of JMX operations to be exposed in order to manage a
JBI container such as installation, deployment, lifecycle management, … (details
on Chapter 6 - JBI specification).
This service is the local access point to all the remote containers JMX operations.
By using this service, the local container can call these operations and so manage
all the remote containers.

- The JNDI Service (org.ow2.petals.communication.jndi.client.JNDIService interface)
provides facilities to connect to a JNDI repository
(http://java.sun.com/products/jndi/).
In PEtALS 1.x and 2.x, the JNDI repository is used to share knowledge between
nodes such as JBI Endpoints and container configuration. This is a central point of
the PEtALS environment and you are, of course, free to choose the JNDI
repository provided by PEtALS or a third party one. This is possible by setting the
JNDI factory properties at the domain level in the topology configuration.
PEtALS 3.0 comes with a new approach where the JNDI repository is replaced by
an extensible and configurable distributed repository.

- The Installation Service
(org.ow2.petals.jbi.management.installation.InstallationServiceMBean interface)
role is to manage the installation (and provide the the lifecycle information) of
the JBI components and shared libraries.

- The Deployment Service
(org.ow2.petals.jbi.management.deployment.DeploymentServiceMBean interface)
role is to manage the deployment (and provide the lifecycle information) of the
service assemblies. The service units bundled into the service assemblies are
deployed to the right component by this service implementation. As a result, JBI
service consumers and providers are activated in the JBI and PEtALS
environment.

The links between these components are at the charge of the PEtALS kernel developer.
The final assembly of different component implementations will result to various
PEtALS behaviours. This is what it is used to created specific PEtALS distributions (see
PEtALS distributions section).

The Fractal architecture of the PEtALS container can be found on the Annex A.

PEtALS JBI Implementation
The current section introduces how JBI artifacts are used in the PEtALS JBI container
and how they help to instanciate the SOA.

The PEtALS container is based on the JBI 1.0 specification and has been certified as a JBI
compliant container by SUN MicroSystems. This certification has been obtained by
running the official SUN JBI test suite with PEtALS as JBI runtime. This suite tests that all
the features defined in the specification are well implemented.

In this section, a ‘container service’ is a software service which is provided by the
container like, for example, the message routing, the exchange security. A ‘JBI service’ is
a service created from a JBI artefact which is used to send, receive and potentially
process JBI messages.

The PEtALS JBI Container
The JBI container is a Java based library which can be used in several forms such as
standalone server, embedded in an entreprise application server, embedded in a
standard Java application, … The JBI container is generally called ‘kernel’ in PEtALS and
implements all the JBI specification.

There is no container lifecycle defined in the JBI specification. Starting PEtALS
instantiates all the software services needed to welcome the JBI artefacts, exchange
messages between JBI services and some additional features which will be detailed later
in this document.

The JBI container can be seen as a service container and like a web application
container, a JBI container is not useful when used alone. To use the container, artifacts
needs to be installed/deployed into the container with the help of management
operations.

Figure 6 - PEtALS Container

Using a JBI Component
The PEtALS components are packaged as ZIP archives which contains the following files:
META-INF/jbi.xml
petals-COMPONENT-NAME.jar
a.jar
b.jar

COMPONENT-NAME is the name of the component. This JAR file contains the classes
which implements the JBI component interface. The other JAR files are third party
libraries which are used by the component implementation.

The JBI component must be installed in the JBI container. The container handles the
component and its descriptor file (the jbi.xml file) which defines JBI properties such the
name, the type (binding component or service engine) and component specific
properties. The component properties will ne used by the component implementation to
configure the component (a pool size, a socket address, …).

The Java classes, which are packaged into the component, are used to create the
component class loader and the container links the component to the container with a
context and the delivery channel used to send and receive JBI messages. Once these
steps are achieved, the component is started but it can not receive and process JBI
messages.

Figure 7 - PEtALS Container and JBI Components

Using a JBI Service Unit
The PEtALS Service Units are packaged as ZIP archives which contains the following
files:
META-INF/jbi.xml
Service.wsdl

The service unit is used to activate consumer or provider endpoints on JBI components.
When the service unit is deployed on the container, this one will create an endpoint with
the information provided in the service unit descriptor (jbi.xml file). A service provider
endpoint is defined by a service name, an interface name, an endpoint name, a WSDL
description (locally from the service unit or remotely with an URL) and some additional
properties.
Once deployed, the messages, which are sent to the endpoint, will be delivered to the
component the service unit is deployed on. It is up to the component to process the
message and to return a message, a response, a fault, or nothing.

Processing a message is specific to the component implementation and is not defined in
the service unit:

- A binding component will generally transform the message into another format
(for example to a SOAP message) and do its job (for example invoking an external
Web Service).

- A service engine will get the message and processes it (orchestration,
transformation, apply rules). The engine will also potentially invoke other JBI
services.

The service unit can not be used alone since the component to deploy the service unit
onto is not defined in its descriptor.

Figure 8 - PEtALS Container and JBI Endpoints

Using a JBI Service Assembly
The PEtALS Service Assemblies are packaged as ZIP archives which contains the
following files:
META-INF/jbi.xml
su-A.zip
su-N.zip

The service assembly contains a collection of service units and a JBI descriptor file
(jbi.xml under META-INF folder). Each service unit is deployed onto the component
which is defined in the service assembly descriptor file. By deploying the service
assembly into the container, it will get all the service units and will try to deploy each
one on the sepcifed component.

Using a JBI Shared Library
The PEtALS shared libraries are packaged as ZIP archives which contains the following
files:
META-INF/jbi.xml
lib-A.zip
lib-N.zip

The shared library contains a collection of Java libraries and a JBI descriptor file (jbi.xml
under the META-INF folder). The descriptor file gives the description of the shared
library (its name, version) and the list of embedded Java libraries.

A shared library is deployed into the container. Once deployed, this artifact may be
potentially used by components to enrich their class loader. This type of artefact is
generally used by components which uses the same libraries and so to limitate the
resources in the PEtALS container.

Using the JBI environment
Now that the container is started, the components are installed and the endpoints are
activated with the help of the service unit deployment, services can be invoked and
messages can be exchanged between service consumers and providers.

Figure 9 - Using PEtALS

In the previous figure, a web service client calls a web service which is hosted by the JBI
container. This web service is just a facade. The JBI service which is consumed by the
facade can be changed as many time as needed. The only condition is to provide the
same interface. This approach is extremely flexible since the JBI service can be a service
composition of other JBI services (and recursively to reach atomic JBI services).

PEtALS JBI Extensions
PEtALS is not a simple JBI implementation, the current chapter introduces specificities
and additionnal features which are not defined in the standard specification.

Distributed Environment
The JBI specification does not deals with any distributed aspect. The main JBI extension
and PEtALS main feature is the distributed approach.

A PEtALS container can share its services and access services which are hosted by other
containers in a transparent way. It means that on the service consumers and providers’
point of view there is no additional configuration like in other JBI containers. Where
other JBI containers provide a distributed approach by connecting containers with the
use of JBI Binding Components plus huge configuration, PEtALS provide this feature
natively without any additional configuration.

Figure 10 - Distributed Service Bus

The previous figure shows that multiple containers with their deployed JBI artifacts are
completelu equal to a single container which holds all these artefacts. The following
sections introduce the software modules which are needed to build this Distributed
Entreprise Service Bus.

The advantages of this distributed environment are:

- Container and connectors can be deployed close to the real services. This is a way
to bypass communication constraints between JBI consumer and JBI provider
like firewall issues and other network constraints.

- Complete control of the inter-container communication layer. As described in the
previous point, each link between consumer and provider may have a specific
configuration. Opening communication ports for JMS, HTTP, FTP, and more is
never possible. Opening and securing only communication for one protocol is
enough for the PEtALS inter-communication protocol. A SOAP service client will
be able to post a JMS message into a topic without any http or JMS port opening.

Technical Registry
The PEtALS JBI services, endpoints, interfaces, WSDL descriptions and container
location are stored in an embedded technical registry. This registry is used by the
PEtALS containers to register services and to route the JBI messages to the right
endpoint.
In order to have a unified vision, the registry entries are replicated among all the PEtALS
nodes using a Distributed HashTable over a multicast channel. This is quite equivalent to
data flooding between registries so when an entry is added to the registry, the data is
send to all the network registries. All the registries have a complete vision of the
services hosted by all the containers.

Note: Since the replicated approach is not scalable at all, the PEtALS v3.0 will come with
a new distributed and extensible registry.

Inter nodes communication
In order to exchange (send/receive) messages between PEtALS containers, PEtALS
extends the JBI specification by introducing a message transporter layer.
In a standard JBI implementation, the Normalized Message Router gets the local
endpoint reference from the local registry and sends the message to a local JBI endpoint.
In the PEtALS approach, once the endpoint is retrieved from the local registry, the
message and the endpoint reference are sent to the transport layer which is in charge to
deliver the message to the JBI endpoint whereever the container it is hosted on. This is
possible by getting the foreign container information where the JBI services is hosted on
from the technical registry. Once all the required information is retrieved, PEtALS
serializes the JBI message to the ‘wire format’ and send it to the foreign container. The
response is sent back from the remote container is needed.
All the containers are linked together by the transporter layer. All the services providers
and consumer scan potentially send messages to each other. All the links which were at
the charge of the distributed application developer are now hidden by the PEtALS
container not only at the service level but also at the communication one.

Figure 11 - Inter nodes communication

The previous figure illustrates two visions of the inter node communication which are
totally equivalent. On the left side, all the containers are linked together by point to

point communication channels. On the right side, all the containers can also
communicate to each other but the links are totally hidden by an abstract
communication layer. At the lower level, the links exist but are not important on the
transport user point of view (in the PEtALS case, the router layer does not care about
links between containers).
JMS is the historical messaging system PEtALS uses to exchange messages between
hosts (OW2 JORAM JMS implementation http://joram.ow2.org). Since PEtALS 2.0, a new
message transporter has been added. The OW2 DREAM project (http://dream.ow2.org)
used for this transporter implemantation is a component-based framework dedicated to
the construction of communication middleware. It provides a component library and a
set of tools to build, configure and deploy middleware implementing various
communication paradigms: group communications, message passing, event-reaction,
publish-subscribe, etc... DREAM is alo build upon the FRACTAL component framework,
which provides support for hierarchical and dynamic composition.
This communication abstraction is also important on the JBI service consumers and
providers side. When standard applications need to create links between service
consumers and providers (for example an application which wants to get weather
forecast from a Yahoo service and get stock values from the Google service) needs to
basically create the links between the client (application under development) and
services (Yahoo, Google, and more). Of course, the ideal solution wil be to add an
abstraction layer to all of this in case of service provider modification (URL,
interface, …). A solution such as an ESB already offers this abstraction layer since the
links are the container responsability.

Management
A specification section (chapter 6) is dedicated to the container management using JMX.
It mainly deals with the JBI artefacts management such as installation, deployment,
starting and stopping. Additionally, the specification defines a set of Apache Ant
(http://ant.apache.org) taks to manage the container from Ant scripts.

PEtALS implements and extends the management requirement of the specification in the
way that additional JMX operations have been added to the specification ones. This is
possible by extending the Managed Beans (MBeans) and adding new ones.

Note : Must group all the MBeans in a specific package
(org.ow2.petals.core.kernel.management) and list them.

Monitoring
PEtALS provides various types of monitoring features:

- Use JMX to store and expose monitoring data. This approach uses the JMX
features provided by the container and adds specific monitoring MBeans.

- Use the Fractal Framework. Since quite every JBI artefact (JBI component, JBI
endpoint, …) and container module are Fractal components, PEtALS uses the
Fractal potential to provide very advanced monitoring data.

There is actually some work to generalize these monitoring approaches to all the
container software components and also to provide monitoring data in more standard

ways (using OASIS WSDM specification and WS-* seems to be good candidates). The
following figure is a general vision of what is planned by adding
aspects/wrappers/controllers to Fractal software components:

Figure 12 - Global Monitoring Vision

The main usage if this monitoring data is to display JBI messages and classify them by
service, endpoint, interface, container, component, … A tool such as the PEtALS
Monitoring and Management WebConsole uses this monitoring data and provide it in a
nice web enabled GUI (of course users can develop their own monitoring client).

Figure 13 - Message Monitoring

Another usage of the monitoring data is for load-balancing. Since PEtALS is a distributed
container, the monitoring data can be a good candidate to choose the right JBI endpoint
depending on its load. More details are given in the load-balancing section.

Kernel Features
The kernel fully implements the JBI specification. Some features have been introduced in
the previous chapters, other ones are defined below.

Domains
PEtALS is not a simple distributed JBI container where all services can be accessed by all
the consumers. To add some visiblity control containers can be classified by domains
and subdomains.

Figure 14 - PEtALS Domains

- PEtALS containers can only communicate with containers which belong to the
same domain.
- Services can be declared as public or private so that private services are only
accessible from containers which belong to the same subdomain.

This domain and subdomain settings are basically called ‘topology’ and are defined in
the topology.xml file under the PEtALS distribution configuration folder.

JBI exchange optimisation
JBI message responses, faults or acknowledgements generates extra trafic between
consumer and provider because the JBI container must transfer all the message
exchange content (the input message, the output one, …) at each pattern step. It is clear
that serializing this data and sending it to the wire are time consuming in the distributed
environment.

By setting the org.ow2.petals.messaging.noack property on the message exchange, the
acknowledgement and error messages will not be sent through the NMR.

Address Resolver
The Adress Resolver acts as the router level (embedded into a router module) to select
the right endpoint to send the message to.

To select the right endpoint, the AR interacts with the Endpoints Registry to get all the
endpoints which provide a valid interface and filter the endpoint list by applying a
strategy (org.ow2.petals.jbi.messaging.routing.strategy.Strategy interface).

The strategy is defined at the Message Exchange level (org.ow2.petals.routing.strategy
property) set by the service consumer. Current strategies are :

- random: Randomly select an endpoint from the input endpoints list.

- default: Select a default strategy from the available ones. No comments in the
code…

- standalone: Randomly select an endpoint from the input endpoints list.

- highest: Select an endpoint based on some weighting given in the message
exchange property.

Note: The strategies are defined at the code level and there is no way to add user ones. This
code has to be refactored to define strategy in a configuration file in order to give the user
the possibility to ad dits own strategies. JAVADOC needs to be added for the current
strategies.

Router Module
The router module has been decomposed into atomic modules
(org.ow2.petals.jbi.messaging.routing.module.Module interface).

Once the router receives a JBI message from the Delivery Channel or from the Transport
layer, it injects this message sequentially in each module for processing.

The standard modules are:

- The address resolver module (AR): The AR selects the good endpoint to send
the message to.

- The transport module: In charge of communication with the transport layer to
send/receive messages.
- The authorization module: Checks that the message can be send to the selected
endpoint. This module uses JAAS for access authorization.

These modules are activated (or not) in the router.cfg configuration file located under
the conf folder of the PEtALS distribution. This part has been designed to be extended by
your own module to add some functionnalities at the router level (logging, reporting, …).

Transport layer
The Transport layer, which is in charge of sending/receiving messages to/from the wire,
is electing a message transport from the message exchange properties.

Selecting the right message transporter depends on the QoS the service consumer has
defined in the org.ow2.petals.transport.qos message exchange property. Possible values
are:

- fast: Assures that the message will be sent in the fast way. The message can be
lost by the local container if something wrong happens and i twill not be possible
to send it again.

- reliable: Assures that the message will be persisted in order to be ressent if
something wrong happens.

In PEtALS v2.x, the technologies used to transport messages are OW2-JORAM (open

source JMS), OW2-Dream (open source Extensible Messaging Framework, used in
TCP/IP mode) and ‘InVM’ (Memory transport in the same Java Virtual Machine).

Security

Transport level security
Since messages are exchanged between nodes, there is a need of securing the data
transmission. This is actually possible by using a SSL channel in the OW2-Dream based
message transporter.

Authorization
It is possible to define authorizations at the service operation level.

A router module is in charge of the authorization; it checks that the user (which belongs
to a group of users, and which is sending a message to the JBI service) is authorized. This
is possible by using the JAAS technology
(http://java.sun.com/javase/technologies/security/) in adition to the JBI message
exchange security subject.
The default implementation of the JAAS authorization login module is based on a simple
configuration file. This router module is configurable and developers can define their
own authorization login module based on other users repositories (LDAP for example).

Hot Deployment
The kernel provides a hot deployment features to avoid any Ant script or JMX
commands. This hot deployment feature allows to install and start JBI artifacts archives
(Component, Service Unit, Service Assembly and Shared Library as ZIP files) by copying
them in the distribution install folder. When the kernel detects a new artifact, it
install/deploy it and process the lifecycle steps to effectively start the artifact.

The same feature is also available for the uninstallation/undeployment steps. By
deleting the artifacts from the uninstall folder, the kernel detects that the artifact must
be stopped and undeployed/uninstalled.

Behind the scenes, the kernel calls the JMX management operations needed to process
all these steps.

These hot deployment/undeployment features are similar to the web application
deployment feature you can find when copying a WAR file into the webapps folder of an
Apache Tomcat container.

Data compression
Since JBI messages are XML based and potentially contain redundant data, the
compression feature has been added when exchanging messages between PEtALS
containers. This compression is done at transport level when a property
(org.ow2.petals.transport.compress) is detected in the message exchange (set by the
service consumer).

Source code

Modules
This section describes the main modules of the PEtALS project. Instructions about how
to get the sources from the OW2 forge and build the project can be found on the PEtALS
Developer Guide (http://forge.objectweb.org/docman/?group_id=213). These modules are
divided in families, their descriptions are given below.

- petals-cdk: The PEtALS Component Development Kit is a framework used to easily
create advanced JBI component wihout any JBI knowledge.

- petals-cdk-api: The CDK API. Used by the CDK core module and the
interceptors.

- petals-cdk-core: The CDK core is the main CDK module which provide all
the features to easily create advanced and perfromant JBI compatible
component without any JBI knowledge. Refer to the CDK chapter to get more
details.

- petals-cdk-interceptors: This module contains some component interceptor
implementations. Refer to the CDK chapter to get more details.

- petals-commons: Contains utilities and common classes used by other modules.

- petals-components: Contains all the PEtALS JBI components (Service Engines
and Binding Components) provided by the project. Refer to the components
section for more details on the available components.
- petals-core: This parent module contains all the modules used to create the
container.
- petals-ant: The ANT task implementation based on the JBI specification
used for container management.
- petals-kernel: The container implementation based on the JBI
specification.
- petals-kernel-api: The kernel API is shared by the core modules and the
container launcher.
- petals-kernel-ext: This module contains some kernel extensions which
are not needed by the container to run. These extensions are generally
added to the container assembly to build specific distributions. A good
example of extension is the OW2-Dragon (http://dragon.ow2.org)
connection implementation, which is added to the Dragon-enabled PEtALS
distribution.
- petals-monitoring: The monitoring module add some monitoring
features based on the Web Service Distributed Management (WSDM)
OASIS specification (http://www.oasis-open.org/committees/wsdm/).
- petals-topology: Used to manipulate the topology classes generated from XML
Schemas.

- petals-demos: This parent module contains usecases and demos based on the
PEtALS container, PEtALS components and service implementation such as Web
Services, JMS Topics, etc…
- petals-distribution: This parent module contains modules used to build specific
distributions (standalone, Platform, quickstart) based on various Fractal
descriptor files. It also contains the petals-launcher module which is the
container launcher.
- petals-jbi: Contains the JBI API code.

- petals-jbi-descriptor: Contains generated classes (from XML schemas) used to
manipulate the JBI descriptors (components, service units, service assemblies,
shared libraries ones).
- petals-jbi-ext: The JBI API extensions. This module contains some additional
classes based on the JBI specification which are not available on the initial JBI
API.
- petals-jmx: This module is a JMX client library implementation which can be
used to manage the PEtALS container. This module is a good alternative to avoid
complex JMX code since JMX client code is not maintainable at all…
- petals-jmx-api: The JMX client API.

- petals-plugins: This parent module contains the Maven
(http://maven.apache.org) plugin used to build and package JBI artefacts from
the source code. It also contains some archetypes (sort of patterns) used by
Maven to create JBI artefacts source code projects.
- petals-security: This parent module contains generic security modules which
are used by the kernel but which can also be used in other projects.
- petals-shared-libraries: This parent module contains some shared libraries
which can be used by JBI components. More details on the shared libraries are
available on the JBI specification.
- petals-tools: The parent module contains tools such as the administration and
monitoring WebConsole, specific JBI components (JBI API exposed in JMX),
installer, deployer, …

- petals-ws: This parent module contains Web Service related libraries such as
WS-Notification, WS-Addressing. All of these libraries are based on the Web
Service specification provided by the OASIS working group.

Distributions
The PEtALS container is distributed as ZIP archive. Once exploded, the folder structure
is detailed below:

- ant: Contains Ant samples for JBI artefact (Component, Service Assembly or
Shared Library) manipulation (installation, lifecycle management, …). This has to
be used with the JBI Ant tasks provided with PEtALS.

- bin: Contains the scripts (*nix and Windows) needed to start, stop and get
container status.

- components (quickstart only): Contains some of the PEtALS JBI components.

- conf: Contains all the container configuration files.

- server.properties: Defines the local container properties such as name,
timeouts, classloader behaviour, …

- topology.xml: Defines the PEtALS network topology. This file contains all
the information (IP addresses, ports, user/password, …) needed by
containers to connect to each other plus some domain specific data.

- router.cfg: Defines the router modules which are engaged.

- loggers.properties: Defines the loggers levels of all the software
components used within PEtALS. Note that each component logger level
can be configured individually.

- install: This is the hot deployment folder. Each JBI artefact (Component, Service
Assembly or Shared Library) which is dropped here is automatically deployed
and started by the container.

- installed: All the installed JBI artefacts (Component, Service Assembly or Shared
Library) are saved in this folder. When an an artefact is deleted from this folder,
it is automatically stopped and undeployed by the container.

- lib: Contains the Java archives (Third party and PEtALS ones) needed by the
PEtALS container.

- licenses: Contains all the third party library licenses.

- repository: Contains all the exploded JBI artefacts (Component, Service
Assembly or Shared Library). Each installed artefact has a dedicated subfolder
which is used as workspace at runtime to build component classloaders, store
resources, … This folder is managed by the container, so please do not
manipulate its resources.

- schema: Contains some XML schéma used to validate JBIi artefact configuration
files.

- uninstalled: Contains all the JBI artefacts which have been successfully been
uninstalled.

- usecases (quickstart only): Contains simple usecases used to introduce PEtALS
and JBI usage.
- webapps: Contains some web applications (WAR files) which are deployed by
PEtALS into the embeded JBI container. This folder is actually only used in the
quickstart distribution to embed the monitoring and managemet web GUI.

- work: This folder is a temporary artefact folder used by the container during the
installation and deployment phases.

Platform
The Platform distribution is the historical and the most advanced one. This distribution
provides the distributed aspects introduced in the previous sections.

Standalone
The Standalone distribution goal is to run alone. Unlike the Platform distribution, there
is no distributed registry (a simple hashtable replaces it), nor inter node message
transport layer (replaced by an in-memory message transport layer).

This distribution is used when the distributed aspect is not the main goal of the
infrastructure. The advantage is that all the distributed notions which are quite complex
are removed from the container. The container is lighter, more robust and the response
time (container startup, endpoint lookup, message transmission) is better.

Quickstart
The quickstart distribution is dedicated to new PEtALS users who want to discover what
an ESB can provide. It is based on the standalone distribution and embeds the
monitoring and management web GUI which is started by the container itself (Note that
it is the Web console which is embeded in the container and not the opposite).

This distribution also comes with a detailed user guide and some use cases based on
PEtALS components which help the user to understand the ESB benefits.

PEtALS JBI Components
All the PEtALS JBI components (Binding Components and Service Engines) are built
upon the Component Development Kit.

The Binding Component collection is composed of:

- The EJB component (Enterprise Java Beans) exposes EJBs hosted on any EJB
container as JBI service.

- The SOAP component is used to expose Web Services as JBI Services or to
expose JBI Services as Web Services.

- The File Transfer component allows transfering files between JBI Services:

- When a file is detected in a folder, it is send to a JBI Service.

- When a message is received on a File activated JBI service, the message
and its attachments are written into files.

- The FTP component (File Transfer Protocol) has the same feature than the File
Transfer component but works with FTP servers and not with a local file system.

- The JMS component (Java Messaging Service) is used to publish/receive
messages to/from JMS queues:

- A JBI message received on the JBI service is translated to a JMS message
and posted to the JMS Queue.

- A JMS message posted to a JMS queue is detected by the component, then

translated to a JBI message and sent to a JBI service.

- The Mail component is used to communicate with mail server with the
IMAP/POP/SMTP protocols.

- A JBI message sent to a Mail activated endpoint is translated to a mail and
sent to the mail server with the SMTP protocol. As a result a mail is sent by
the mail server according to the recipient address.

- The JBI component detects a mail on a mail server with the POP or IMAP
protocol. Once the mail is translated to a JBI message, it is transfered to a
JBI service.

- The XMPP component (eXtensible Messaging and Presence Protocol) is used to
send/receive messages to/from a Jabber server.

- A XMPP activated JBI service translates the incoming JBI message and
send it to a Jabber server using the XMPP protocol.

- When a message is received by the XMPP component (acts as a Jabber
client), it is translated to a JBI message and sent to a JBI service.
- The XQuare component is used to access to databases. It uses XQuery to query a
database through JDBC. Due to some XQuare limitations, an additional mode with
native SQL has been added.

The PEtALS Service Engines are:

- The BPEL engine (Business Process Execution Language) is used to orchestrate
JBI services. It is actually based on the OW2 Orchestra BPEL engine.

- The CSV engine (Coma Separated Values) is used to transform XML message
to/from CSV format.

- The EIP engine (Enterprise Integration Patterns) is used for lightweight
orchestration. Details about patterns can be found in
(http://www.enterpriseintegrationpatterns.com). Some of the patterns provided
by this component are:

- The router to route messages to JBI service based on the message content
(also named CBR for Content Based Router)

- The splitter splits XML message into parts and send these messages to
different JBI services.

- The aggregator aggregates the results from multiple JBI service calls into a
single message
- The JSR181 engine is used to expose JAXWS annotated Java classes as JBI
services.

- The Quartz engine launches activities based on a crontab definition.

- The validation engine validates the content of the JBI message using a XSD

definition.

- The XSLT engine transforms JBI messages using an XSLT processor and XSLT
files.

Some additional components such as a rules (based on JBOSS Drools), script (Groovy)
ones are still under development.

PEtALS Tools
PEtALS is not only a JBI container and some JBI components. Various tools have been
developed around this project in order to facilitate the users and developers life. This
section describes the main ones.

PEtALS WebConsole
The PEtALS WebConsole is a Web GUI providing management and monitoring features
for PEtALS containers.

The WebConsole uses the extended JMX API of the PEtALS container to:
- Collect data from all the containers of the management domain, processes this
data and display messages content and useful statistics like service response
time, service and container load, queue sizes, message repartition…

- Manage the JBI artefacts. It is possible to start, stop, deploy, and undeploy
artefacts from the Web browser and to check their states.

Figure 15 - WebConsole Monitoring

The WebConsole also provides:

- an embeded JBI client to invoke JBI services directly from the Web browser

- a module to configure services (Service Unit and Service Assembly generation) on
the server side without any generation on the client side

Figure 16 - WebConsole Embedded Client

High Level Architecture

Figure 17 - WebConsole Architecture

The WebConsole is a single access point to manage containers distributed over several
domains. The Web Application hosted on any Web Application server is connected to an
intermediate layer (the data collector) which is in charge of establishing connections to
the monitoring and management PEtALS container API.

A command (monitoring or management) sent to a container from the client (the web
application) transits through the data collector layer and is routed to the right container.
The actual architecture is based on the JMX technology. All the communication between
or the parties uses JMX to exchange commands and datas.

Eclipse Plugins
Eclipse plugins provides advanced solution for developers:

- Create Service Units for the PEtALS JBI components with a set of wizard pages
(No more XML file to edit). It is also used to package the SUs into SAs in order to
be deployed directly in PEtALS. The wizards are automatically generated from
the JBI component description files (XSD files).

- Create JBI component skeletons. This will help the component developer to start
new projects based on the PEtALS CDK directly from the Eclipse IDE.

Figure 18 - Create a Service Unit with Eclipse Plugin

Note: Future work on the Eclipse plugins focuses on the containers monitoring and
management integration.

Annexe A – Fractal Architecture

Figure 19 - JBI Messaging Composite

Figure 20 - JBI Management Composite

Figure 21 - Communication Composite

Figure 22 - Platform Composite

Figure 23 - Transporter Composite

PEtALS ESB Architecture

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PEtALS ESB Architecture