Exposing a Java class as a POJO service (Provides mode)UsageThe POJO that you want to develop must follow certain constraints :
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>
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 |
Parameter | Description | Default | Required |
---|---|---|---|
class-name | The name of the Java class to expose as a service. | -
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Yes
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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
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 :
|
- | 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:
|
no |
MessageExchangeAcceptorRelativeDurations | The aggregated durations of the working message exchange acceptors on the last sample. | n-tuple value containing, in nanosecond:
|
no |
MessageExchangeProcessorAbsoluteDurations | The aggregated durations of the working message exchange processor since the last startup of the component. | n-tuple value containing, in milliseconds:
|
no |
MessageExchangeProcessorRelativeDurations | The aggregated durations of the working message exchange processor on the last sample. | n-tuple value containing, in milliseconds:
|
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:
|
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:
|
n-tuple value containing, in millisecond:
|
no |
ServiceProviderInvocationsResponseTimeRel | The aggregated response times of the service provider invocations on the last sample, grouped by:
|
n-tuple value containing, in millisecond:
|
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 |
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No more thread is available in the message exchange acceptor thread pool |
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No more thread is available to run a message exchange processor |
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Dedicated alerts
No dedicated alert is available.