Petals-SE-POJO 2.3.1+

Exposing a Java class as a POJO service (Provides mode)

Usage

The POJO that you want to develop must follow certain constraints :

  • no specific interface implementation is required.
  • if a public setComponentContext(ComponentContext context) setter method is defined, the component set its ComponentContext instance with this method at the initialization of the Service Unit.
  • if a public setDeliveryChannel(DeliveryChannel channel) setter method is defined, the component set its DeliveryChannel instance with this method at the initialization of the Service Unit.
  • if a public setJBIListener(AbstractJBIListener jbiListener) setter method is defined, the component set its JBIListener instance with this method at the initialization of the Service Unit.
  • if a public setLogger(Logger logger) setter method is defined, the component set its Logger instance with this method at the initialization of the Service Unit.
  • if a public void init() method is defined, the component invoke it at the initialization of the Service Unit.
  • a public boolean onExchange(Exchange exchange) MUST be provided.
  • an public boolean onAsyncExchange(Exchange exchange, AsyncContext asyncContext) CAN be provided, optionally.
  • all methods can throw exceptions.
  • FaultException are used to represent business faults (as declared in the WSDL contract): the XML content of the Fault is passed to the constructor of the exception.
  • only one instance of the POJO class is instanciated by the component, so the POJO must be thread-safe
  • to prevent memory leak, using the singleton pattern is to prohibit

When building such a Service Unit using Maven, the classes ComponentContext and DeliveryChannel are provided by the dependency petals-jbi, AbstractJBIListener and AsyncContext by petals-cdk-core, and Exchange by petals-cdk-api. These dependencies must be defined using the scope provided as they are provided by the container.

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Process a service in the synchronous way

A sample class following the above rules for processing service in the synchronous way:

package test;
import java.util.logging.Level;
[...]
import org.ow2.petals.component.framework.listener.AbstractJBIListener;

public class SamplePojoService {
  AbstractJBIListener jbiListener;
  Logger logger;
  ComponentContext ctx;

  public void setJBIListener(AbstractJBIListener jbiListener) {
    this.jbiListener = jbiListener;
  }
  public void setComponentContext(ComponentContext ctx) {
    this.ctx = ctx;
  }
  public void setLogger(Logger logger) {
    this.logger = logger;
  }

  public boolean onExchange(Exchange exchange)
    throws MessagingException {
    [...]
    jbiListener.sendSync(anotherExchange);
    [...]
    return true;
  }

  public void init() {
    logger.log(Level.INFO, "Sample Pojo inits.");
  }
}

The method onExchange(Exchange exchange) is invoked when an exchange is received from the component that is addressed to the current POJO endpoint.
The POJO must process the service in that method.
The POJO can invoke any 'sub-service' during its processing by synchronous invocations using the jbiListener instance.
If the POJO service must reply with a message OUT or FAULT, according to the MEP, the method must build and set the message to the current exchange.
Then, the method must return true to delegate the effective send back of the response or acknowledgment (according to the MEP) to the CDK.
The exceptions should be handled properly during the processing of the method, and set accordingly as error or fault to the exchange.
However, mishandled exceptions will be handled by the CDK as generic exceptions.

Process a service in the asynchronous way

A sample class following the above rules for processing service in the asynchronous way:

package test;
import java.util.logging.Level;
[...]
import org.ow2.petals.component.framework.listener.AbstractJBIListener;

public class SamplePojoService {
  AbstractJBIListener jbiListener;
  Logger logger;
  ComponentContext ctx;

  public void setJBIListener(AbstractJBIListener jbiListener) {
    this.jbiListener = jbiListener;
  }
  public void setComponentContext(ComponentContext ctx) {
    this.ctx = ctx;
  }
  public void setLogger(Logger logger) {
    this.logger = logger;
  }

  public boolean onExchange(Exchange exchange)
    throws MessagingException {
    [...]
    MyAsyncContext myAsyncContext = new MyAsyncContext(...);
    [...]
    jbiListener.sendASync(anotherExchange, myAsyncContext);
    [...]
    return false;
  }

  public boolean onAsyncExchange(Exchange subExchange, AsyncContext asyncContext)
    throws MessagingException {
    [...]
    Exchange originalExchange = asyncContext.getOriginalExchange();
    [...]
    jbiListener.send(originalExchange);
    [...]
    return true;
  }

  public void onExpiredAsyncJBIMessage(Exchange subExchange, AsyncContext asyncContext)
    throws MessagingException {
    [...Handle here the subExchange timeout...]
  }

  public void init() {
    logger.log(Level.INFO, "Sample Pojo Async inits.");
  }
}

Processing a service in asynchronous way is the best approach when targeting performance, but it's more tedious to develop, and demands an average level in Petals development.
Basically, all is in the data that permit to correlate asynchronous sent exchange and their asynchronous response.
The original exchange is the received by the component and the process of the service start in the onExchange(Exchange exchange) method.
The method create an asynchronous context, to set the data.
The method can create any 'sub-exchange' and send then asynchronously, with the asynchronous context as parameter.
Then the onExchange(Exchange exchange) returns false, as the response or the acknowledgment of the original exchange is not yet ready to be sent back.
Any asynchronous response from the 'sub-exchange' comes back in the onAsyncExchange(Exchange subExchange, AsyncContext asyncContext) method. During the process of this method, the 'sub-exchange' must be handled according to the MEP, and the returns true of the method let the CDK send the 'sub-exchange' to the partner.
Once all 'sub-exchanges' are received, the 'original' exchange can be retrieve from the asynchronous context and the response or acknowledgement send back explicitly.
If a 'sub-service' do not response at time, the onExpiredAsyncJBIMessage(...) method will be invoked by the CDK. You must handle the timeout of the 'sub-exchange' in this method.
Note that once a sendAsync(...) has expired, the POJO does not have the ownership of the exchange anymore (because it was sent but never came back) and can't access anything else than the exchangeId and the exchange status! The AsyncContext, which can be subclassed when needed, is there to store needed information in these situations.

Service Configuration

Service Unit descriptor

The POJO JBI descriptor must contain a Provides section for each POJO to expose in the JBI bus.

AN example of the POJO SU:

<?xml version="1.0" encoding="UTF-8"?>
<!-- JBI descriptor for PEtALS' "petals-se-pojo" (POJO), version 2.0 -->
<jbi:jbi version="1.0"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xmlns:jbi="http://java.sun.com/xml/ns/jbi"
  xmlns:pojo="http://petals.ow2.org/components/pojo/version-2.0"
  xmlns:petalsCDK="http://petals.ow2.org/components/extensions/version-4.0"
  xmlns:generatedNs="http://POJO/test">
  <!-- Import a Service into PEtALS or Expose a PEtALS Service => use a BC. -->
  <jbi:services binding-component="false">
     <!-- Import a Service into PEtALS => provides a Service. -->
     <jbi:provides
       interface-name="generatedNs:POJO"
       service-name="generatedNs:POJOService"
       endpoint-name="POJOServiceEndpoint">
       <!-- CDK specific elements -->
       <petalsCDK:wsdl xsi:nil="true" />
       <!-- Component specific elements -->
       <pojo:class-name>test.SamplePojoService</pojo:class-name>
     </jbi:provides>
  </jbi:services>
</jbi:jbi>
Configuration of a Service Unit to provide a service (JBI)

Parameter Description
Default
Required
provides Describe the JBI service that will be exposed into the JBI bus. Interface (QName), Service (QName) and Endpoint (String) attributes are required. - Yes

Configuration of a Service Unit to provide a service (CDK)

Parameter Description
Default
Required
timeout Timeout in milliseconds of a synchronous send. This parameter is used by the method sendSync (Exchange exchange) proposes by the CDK Listeners classes.
Set it to 0 for an infinite timeout.
30000 No
exchange-properties This sections defines the list of properties to set to the JBI exchange when processing a service. - No
message-properties This sections defines the list of properties to set to the JBI message when processing a service. - No
validate-wsdl Activate the validation of the WSDL when deploying a service unit. true No
wsdl
Path to the WSDL document describing services and operations exposed by the provided JBI endpoints defined in the SU.
The value of this parameter is :
  • an URL
  • a file relative to the root of the SU package
    If not specified, a basic WSDL description is automaticaly provided by the CDK.
- No
forward-attachments
Defines if attachment will be forwarded from IN message to OUT message.
false No
forward-message-properties
Defines if the message properties will be forwarded from IN message to OUT message. false No
forward-security-subject
Defines if the security subject will be forwarded from IN message to OUT message. false No


Configuration of a Service Unit to provide a service (POJO)
Parameter Description Default Required
class-name The name of the Java class to expose as a service.
-
Yes

Interceptor

Example of an interceptor configuration:

<?xml version="1.0" encoding="UTF-8"?>
<!--...-->
<petalsCDK:su-interceptors>
  <petalsCDK:send>
    <petalsCDK:interceptor name="myInterceptorName">
      <petalsCDK:param name="myParamName">myParamValue</petalsCDK:param>
      <petalsCDK:param name="myParamName2">myParamValue2</petalsCDK:param>
    </petalsCDK:interceptor>
  </petalsCDK:send>
  <petalsCDK:accept>
    <petalsCDK:interceptor name="myInterceptorName">
      <petalsCDK:param name="myParamName">myParamValue</petalsCDK:param>
    </petalsCDK:interceptor>
  </petalsCDK:accept>
  <petalsCDK:send-response>
    <petalsCDK:Interceptor name="myInterceptorName">
      <petalsCDK:param name="myParamName">myParamValue</petalsCDK:param>
    </petalsCDK:Interceptor>
  </petalsCDK:send-response>
  <petalsCDK:accept-response>
    <petalsCDK:Interceptor name="myInterceptorName">
      <petalsCDK:param name="myParamName">myParamValue</petalsCDK:param>
    </petalsCDK:Interceptor>
  </petalsCDK:accept-response>
</petalsCDK:su-interceptors>
<!--...-->

Interceptors configuration for SU (CDK)

Parameter Description Default Required
send Interceptor dedicated to send phase, for an exchange sent by a consumer - No
accept Interceptor dedicated to receive phase, for an exchange received by a provider - No
send-response Interceptor dedicated to send phase, for an exchange (a response) received by a consumer - No
accept-response Interceptor dedicated to receive phase, for an exchange sent (a response) by a provider - No
interceptor - name Logical name of the interceptor instance. It can be referenced to add extended parameters by a SU Interceptor configuration. - Yes
param[] - name The name of the parameter to use for the interceptor for this SU - No
param[] The value of the parameter to use for the interceptor for this SU - No

Service Unit content

The POJO class(es) and their depending libraries must be set as JAR(s) file(s) at the root directory of the POJO Service
Unit package.

The Service Unit must contain the following elements, packaged in an ZIP archive:

  • The META-INF/jbi.xml descriptor file, has described above.
  • At least one jar containing the POJO class to expose
    service-unit.zip
    + META-INF
      - jbi.xml (as defined above)
      - mypojoclasses.jar
    

Component Configuration

Configuration of the component, CDK part

Parameter Description Default Scope
acceptor-pool-size The size of the thread pool used to accept Message Exchanges from the NMR. Once a message is accepted, its processing is delegated to the processor pool thread. 1
Runtime
acceptor-retry-number Number of tries to submit a message exchange to a processor for processing before to declare that it cannot be processed. 40
Installation
acceptor-retry-wait Base duration, in milliseconds, to wait between two processing submission tries. At each try, the new duration is the previous one plus this base duration. 250
Installation
acceptor-stop-max-wait The max duration (in milliseconds) before, on component stop, each acceptor is stopped by force. 500
Runtime
processor-pool-size The size of the thread pool used to process Message Exchanges. Once a message is accepted, its processing is delegated to one of the thread of this pool. 10 Runtime
processor-max-pool-size The maximum size of the thread pool used to process Message Exchanges. The difference between this size and the processor-pool-size represents the dynamic threads that can be created and destroyed during overhead processing time.
50
Runtime
processor-keep-alive-time When the number of processors is greater than the core, this is the maximum time that excess idle processors will wait for new tasks before terminating, in seconds.
300
Runtime
processor-stop-max-wait The max duration (in milliseconds) of message exchange processing on stop phase (for all processors).
15000
Runtime
time-beetween-async-cleaner-runs The time (in milliseconds) between two runs of the asynchronous message exchange cleaner.
2000
Installation
properties-file Name of the file containing properties used as reference by other parameters. Parameters reference the property name using a placeholder in the following pattern ${myPropertyName}. At runtime, the expression is replaced by the value of the property.

The properties file can be reloaded using the JMX API of the component. The runtime configuration MBean provides an operation to reload these place holders. Check the service unit parameters that support this reloading.

The value of this parameter is :
  • an URL
  • a file relative to the PEtALS installation path
  • an absolute file path
  • an empty value to stipulate a non-using file.
- Installation
monitoring-sampling-period Period, in seconds, of a sample used by response time probes of the monitoring feature.
300
Installation

Definition of CDK parameter scope :

  • Installation: The parameter can be set during the installation of the component, by using the installation MBean (see JBI specifications for details about the installation sequence). If the parameter is optional and has not been defined during the development of the component, it is not available at installation time.
  • Runtime: The paramater can be set during the installation of the component and during runtime. The runtime configuration can be changed using the CDK custom MBean named RuntimeConfiguration. If the parameter is optional and has not been defined during the development of the component, it is not available at installation and runtime times.

Interceptor

Interceptors can be defined to inject some post or pre processing in the component during service processing.

Using interceptor is very sensitive and must be manipulate only by power users. An non properly coded interceptor engaged in a component can lead to uncontrolled behaviors, out of the standard process.

Example of an interceptor configuration:

<?xml version="1.0" encoding="UTF-8"?>
<!--...-->
<petalsCDK:component-interceptors>
  <petalsCDK:interceptor active="true" class="org.ow2.petals.myInterceptor" name="myInterceptorName">
    <petalsCDK:param name="myParamName">myParamValue</petalsCDK:param>
    <petalsCDK:param name="myParamName2">myParamValue2</petalsCDK:param>
  </petalsCDK:interceptor>
</petalsCDK:component-interceptors>
<!--...-->

Interceptors configuration for Component (CDK)

Parameter Description Default Required
interceptor - class Name of the interceptor class to implement. This class must extend the abstract class org.ow2.petals.component.common.interceptor.Interceptor. This class must be loadable from the component classloader, or in a dependent Shared Library classloader. - Yes
interceptor - name Logical name of the interceptor instance. It can be referenced to add extended parameters by a SU Interceptor configuration. - Yes
interceptor - active If true, the Interceptor instance is activated for every SU deployed on the component.
If false, the Interceptor can be activated:
-by the InterceptorManager Mbean at runtime, to activate the interceptor for every deployed SU.
-by a SU configuration
- Yes
param[] - name The name of the parameter to use for the interceptor. - No
param[] The value of the parameter to use for the interceptor. - No

Monitoring the component

Using metrics

Several probes providing metrics are included in the component, and are available through the JMX MBean 'org.ow2.petals:type=custom,name=monitoring_<component-id>', where <component-id> is the unique JBI identifier of the component.

Common metrics

The following metrics are provided through the Petals CDK, and are common to all components:

Metrics, as MBean attribute Description Detail of the value Configurable
MessageExchangeAcceptorThreadPoolMaxSize The maximum number of threads of the message exchange acceptor thread pool integer value, since the last startup of the component yes, through acceptor-pool-size
MessageExchangeAcceptorThreadPoolCurrentSize The current number of threads of the message exchange acceptor thread pool. Should be always equals to MessageExchangeAcceptorThreadPoolMaxSize. instant integer value no
MessageExchangeAcceptorCurrentWorking The current number of working message exchange acceptors. instant long value no
MessageExchangeAcceptorMaxWorking The max number of working message exchange acceptors. long value, since the last startup of the component no
MessageExchangeAcceptorAbsoluteDurations The aggregated durations of the working message exchange acceptors since the last startup of the component. n-tuple value containing, in nanosecond:
  • the maximum duration,
  • the average duration,
  • the minimum duration.
no
MessageExchangeAcceptorRelativeDurations The aggregated durations of the working message exchange acceptors on the last sample. n-tuple value containing, in nanosecond:
  • the maximum duration,
  • the average duration,
  • the minimum duration,
  • the 10-percentile duration (10% of the durations are lesser than this value),
  • the 50-percentile duration (50% of the durations are lesser than this value),
  • the 90-percentile duration (90% of the durations are upper than this value).
no
MessageExchangeProcessorAbsoluteDurations The aggregated durations of the working message exchange processor since the last startup of the component. n-tuple value containing, in milliseconds:
  • the maximum duration,
  • the average duration,
  • the minimum duration.
no
MessageExchangeProcessorRelativeDurations The aggregated durations of the working message exchange processor on the last sample. n-tuple value containing, in milliseconds:
  • the maximum duration,
  • the average duration,
  • the minimum duration,
  • the 10-percentile duration (10% of the durations are lesser than this value),
  • the 50-percentile duration (50% of the durations are lesser than this value),
  • the 90-percentile duration (90% of the durations are upper than this value).
no
MessageExchangeProcessorThreadPoolActiveThreadsCurrent The current number of active threads of the message exchange processor thread pool instant integer value no
MessageExchangeProcessorThreadPoolActiveThreadsMax The maximum number of threads of the message exchange processor thread pool that was active integer value, since the last startup of the component no
MessageExchangeProcessorThreadPoolIdleThreadsCurrent The current number of idle threads of the message exchange processor thread pool instant integer value no
MessageExchangeProcessorThreadPoolIdleThreadsMax The maximum number of threads of the message exchange processor thread pool that was idle integer value, since the last startup of the component no
MessageExchangeProcessorThreadPoolMaxSize The maximum size, in threads, of the message exchange processor thread pool instant integer value yes, through http-thread-pool-size-max
MessageExchangeProcessorThreadPoolMinSize The minimum size, in threads, of the message exchange processor thread pool instant integer value yes, through http-thread-pool-size-min
MessageExchangeProcessorThreadPoolQueuedRequestsCurrent The current number of enqueued requests waiting to be processed by the message exchange processor thread pool instant integer value no
MessageExchangeProcessorThreadPoolQueuedRequestsMax The maximum number of enqueued requests waiting to be processed by the message exchange processor thread pool since the last startup of the component instant integer value no
ServiceProviderInvocations The number of service provider invocations grouped by:
  • interface name, as QName, the invoked service provider,
  • service name, as QName, the invoked service provider,
  • invoked operation, as QName,
  • message exchange pattern,
  • and execution status (PENDING, ERROR, FAULT, SUCCEEDED).
integer counter value since the last startup of the component no
ServiceProviderInvocationsResponseTimeAbs The aggregated response times of the service provider invocations since the last startup of the component grouped by:
  • interface name, as QName, the invoked service provider,
  • service name, as QName, the invoked service provider,
  • invoked operation, as QName,
  • message exchange pattern,
  • and execution status (PENDING, ERROR, FAULT, SUCCEEDED).
n-tuple value containing, in millisecond:
  • the maximum response time,
  • the average response time,
  • the minimum response time.
no
ServiceProviderInvocationsResponseTimeRel The aggregated response times of the service provider invocations on the last sample, grouped by:
  • interface name, as QName, the invoked service provider,
  • service name, as QName, the invoked service provider,
  • invoked operation, as QName,
  • message exchange pattern,
  • and execution status (PENDING, ERROR, FAULT, SUCCEEDED).
n-tuple value containing, in millisecond:
  • the maximum response time,
  • the average response time,
  • the minimum response time,
  • the 10-percentile response time (10% of the response times are lesser than this value),
  • the 50-percentile response time (50% of the response times are lesser than this value),
  • the 90-percentile response time (90% of the response times are lesser than this value).
no

Dedicated metrics

No dedicated metric is available.

Receiving alerts

Several alerts are notified by the component through notification of the JMX MBean 'org.ow2.petals:type=custom,name=monitoring_<component-id>', where <component-id> is the unique JBI identifier of the component.

To integrate these alerts with Nagios, see Receiving Petals ESB defects in Nagios.

Common alerts

Defect JMX Notification
A message exchange acceptor thread is dead
  • type: org.ow2.petals.component.framework.process.message.acceptor.pool.thread.dead
  • no user data
No more thread is available in the message exchange acceptor thread pool
  • type: org.ow2.petals.component.framework.process.message.acceptor.pool.exhausted
  • no user data
No more thread is available to run a message exchange processor
  • type: org.ow2.petals.component.framework.process.message.processor.thread.pool.exhausted
  • no user data

Dedicated alerts

No dedicated alert is available.

Labels

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