Sunday, March 2, 2014

ESB Performance Round 7.5

WSO2 has carried out a performance testing of latest ESB release, WSO2 ESB 4.8.1. In WSO2 ESB Performance Round 7.5 it compares WSO2 ESB 4.8.1 with other competitive ESB products, Mule ESB 3.4.0, Talend-SE 5.3.1 and UltraESB 2.0.0.

Basic observations are as follows.



Tuesday, July 16, 2013

How to Build WSO2 Code

Although WSO2 is open source many people were having problem with checking out the WSO2 source code and building WSO2 products. Here are the simple steps to do it.
Note that at the moment ongoing development happens inside the trunk with version 4.2.0 SNAPSHOT. Last released WSO2 code is located in branch version 4.1.0 with Carbon platform version 4.1.2.

Build the trunk


  1. Checkout Orbit from https://svn.wso2.org/repos/wso2/carbon/orbit/trunk/
  2. Checkout Kernel from https://svn.wso2.org/repos/wso2/carbon/kernel/trunk/
  3. Checkout Platform from https://svn.wso2.org/repos/wso2/carbon/platform/trunk/
  4. Install Apache Maven 3 in your computer.
  5. Go to the checked out directories and build with Maven of orbit, kernel and platform code respectively. (Use command, mvn clean install)
  6. If any errors comes with tests use the command mvn clean install -Dmaven.test.skip=true
  7. If the build is properly building and you are fortunate you will get all the products as zip files in each product. For example WSO2 BAM will be there in platform/trunk/products/bam/modules/distribution/target directory.
  8. But most probably you will not be able to build all the products well at the same time and it will take much time as well. So you can build the product only you want as follows. Comment the products module in platform/trunk/pom.xml . Then after building all three orbit, kernel and platform, you can manually build the product/s you want. For example if you only want to build WSO2 BAM, go to platform/trunk/products/bam and build with command mvn clean install -Dmaven.test.skip=true

Build the Branch 4.1.0

  1. Checkout orbit from https://svn.wso2.org/repos/wso2/carbon/orbit/branches/4.1.0/
  2. Checkout kernel from https://svn.wso2.org/repos/wso2/carbon/kernel/branches/4.1.0/
  3. Checkout platform from https://svn.wso2.org/repos/wso2/carbon/platform/branches/4.1.0/
  4. Follow the exact steps 4, 5 and 6 mentioned under the topic, "Build the trunk".
  5. In 7th step, use the directory path, branches/4.1.0/products/bam/2.3.0/modules/distribution/target as the BAM pack location.
  6. Then follow the 8th step by commenting the product module in branches/4.1.0/pom.xml and building the BAM in location, branches/4.1.0/products/bam/2.3.0

Build a Tag

When already there is a released product, best way to build it, is by checking out the tag of the released version. The reason is that even the branch may be committed after the release by a mistake.
For this example lets continue with WSO2 BAM 2.3.0. It has orbit version 4.1.0, kernel version 4.1.0 and platform version 4.1.2. You can checkout these three from https://svn.wso2.org/repos/wso2/carbon/orbit/tags/4.1.0/ , https://svn.wso2.org/repos/wso2/carbon/kernel/tags/4.1.0/ and https://svn.wso2.org/repos/wso2/carbon/platform/tags/4.1.2/ . Then continue building in the same way as earlier.



Monday, January 7, 2013

Writing a Custom Mediator for WSO2 ESB - Part 3

This is the last part of blog post series about creating a WSO2 ESB mediator. Older parts are,
  1. Part 1
  2. Part 2
In this post I will explain the UI component of a ESB mediator using the BAM mediator (Carbon version 4.0.5). UI component (i.e.: org.wso2.carbon.mediator.bam.ui) is responsible for the BAM mediator specific UIs in the following UI.

Mediator UI



When BAM mediator is selected in the above mediator sequence (there is only the BAM mediator is available here anyway) the UI located under the sequence UI, is specified in the mediator UI component. Anyway not all the UI under it comes from the UI component. UI between the bar named Mediator and Update button comes from the UI component. Actually this is the edit-mediator.jsp JSP located in the resources package in org.wso2.carbon.mediator.bam.ui component.
After the changes are made on UI the user can click on the above mentioned Update button. This event will call the update-mediator.jsp JSP adjacent to the edit-mediator.jsp JSP.

When switch to source view is clicked the following source appears.


And you can return back to design view by clicking on switch to design view link. This toggling mechanism need the implementation of UI component. In simple terms this functionality need the implementation of,
  1. BamMediator UI class - similar to BamMediator class in backend component
  2. serialize method - similar to serializeSpecificMediator method in BamMediatorSerializer class in backend component
  3. build method - similar to createSpecificMediator method in BamMediatorFactory class in backend component

Abstract Mediator Class (UI)


The difference of UI component with backend component is, that both serialize method and build method are included in the BamMediator UI class. BamMediator UI class can be found in org.wso2.carbon.mediator.bam.ui package.
BamMediator class should inherit from org.wso2.carbon.mediator.service.ui.AbstractMediator.
And also it should implement getTagLocalName method, similar to getTagQName used in backend. And also the serialize and build methods as mentioned earlier should be implemented.

public class BamMediator extends AbstractMediator {

    public String getTagLocalName() {

    }

    public OMElement serialize(OMElement parent) {

    }

    public void build(OMElement omElement) {

    }

}

Abstract Mediator Service Class


Every mediator UI component should consists of a Mediator Service class. In this example BamMediatorService is the class which implements the required settings of the UI. Let's explain with the example.

public class BamMediatorService extends AbstractMediatorService {

    public String getTagLocalName() {
        return "bam";
    }

    public String getDisplayName() {
        return "BAM";
    }

    public String getLogicalName() {
        return "BamMediator";
    }

    public String getGroupName() {
        return "Agent";
    }

    public Mediator getMediator() {
        return new BamMediator();
    }

}

As the example says every Mediator Service should inherit the org.wso2.carbon.mediator.service.AbstractMediatorService class.
Note how the name BAM is used as the sequence editor under the sub menu item named Agent. See how the getMediator method is used to execute the BamMediator UI class which we have discussed earlier.

Bundle Activator Class


Unlike other Carbon bundles where Bundle Activator is defined in the backend bundle, in a mediator class, the Bundle Activator is defined in the  UI bundle. In this example it is BamMediatorActivator class.

Basically the Bundle Activator should inherit the org.osgi.framework.BundleActivator class and should implement start and stop methods. For further information read this article.

Properties props = new Properties();

bundleContext.registerService(MediatorService.class.getName(), new BamMediatorService(), props);

Note how the BamMediatorService class is used.

Congratulations, you have finished the post series of how to write a custom mediator with WSO2 ESB. If you could not understand this well, most probably that is because you are not familiar with WSO2 Carbon platform. If you search more you will be able to catch them.

Friday, January 4, 2013

Writing a Custom Mediator for WSO2 ESB - Part 2

Let's continue from the previous post, Part 1. As there were several changes and fixes happened to BAM mediator, there we are taking the example of two latest components,
  1. org.wso2.carbon.mediator.bam version 4.0.5 - backend component
  2. org.wso2.carbon.mediator.bam.ui version 4.0.5 - UI component
As you can see, there is no services.xml file exists in the backend component. There are two files namely org.apache.synapse.config.xml.MediatorFactory and org.apache.synapse.config.xml.MediatorSerializer containing the class names (with package name) of Mediator Factory and Mediator Serializer. Let's discuss the usage of these 2 classes.

Mediator Factory


In WSO2 ESB, each mediator is created using the Factory design pattern. When the ESB starts each mediator is created using a Mediator Factory. The programmer is given the opportunity to write the Mediator Factory as a single class. In this example, the factory class is org.wso2.carbon.mediator.bam.xml.BamMediatorFactory that contains all the instantiating code relevant to the mediator. Factory class is the code that generates the mediator based on the mediator XML (XML specification of the mediator in the ESB sequence). In this factory the configuration information should be extracted from the XML and should create a mediator based on that configuration.

public Mediator createSpecificMediator(OMElement omElement, Properties properties) {

}

This method should be implemented which takes the XML as an OMElement and returns the Mediator to be produced. Here it is an instance of the BamMediator class we have defined in the parent package.
And also in this method it can access the secondary storage (e.g.: Registry) as the method is not performance critical. (This method will run only at the creation stage of a mediator.)

public QName getTagQName() {

}

This method should also be implemented to return the QName of the XML of the specific mediator. In BAM mediator it has the name "bam".

Mediator Serializer

Mediator Serializer does the reverse of the Mediator Factory. It creates the XML, related to the mediator, back from the Mediator class. (Here it is from BamMediator)

public OMElement serializeSpecificMediator(Mediator mediator) {

}

This method should implement which does the above said conversion. (serialization) It takes the Mediator and returns the generated XML, related to the mediator.

public String getMediatorClassName() {

}

And also this should be implemented to return the Mediator's class name.

Now let's start discuss about the most important class, the Mediator class, here the BamMediator class.

Mediator Class

This is the class used while the ESB is running for the purpose of mediation. As this class is executed in run time it should be designed with care avoiding unnecessary performance degrading actions. And also because this class is executed in parallel threads, should be careful on concurrency issues and make them thread safe.
Mediator class should always extend the AbstractMediator class.

public boolean isContentAware() {
    return true;
}


The above method must be included in the Mediator class if the mediator is intended to interact with the MessageContext.
mediate is the most important method that should be implemented.


public boolean mediate(MessageContext messageContext) {

}

mediate method is given the MessageContext of the message, which is unique to an each request passing through the mediation sequence. The return boolean value should be true if the mediator was successfully executed and false if not.

Note that global variables in the Mediator class may cause race condition as different threads of the mediation sequence may access the same global variable. It can be prevented by one of the following techniques.
  1. Using local variables inside the method
  2. Storing variables in the MessageContext as Properties
  3. Using thread local variables
Best way to handle this issue is possible with first technique if the mediator is not that complex. And the third technique should be used with care if want to use due to the risk of memory leaks.

Let's discuss about the UI package in the next part (Part 3).

Thursday, December 27, 2012

Facebook Login Problems

One of the main problems with Facebook login is forgetting the password. And loading time of a facebook page is also a big issue with low bandwidth Internet connections.

Most problems can be resolved with the Facebook help. For example a Facebook login problem can be resolved from here. The best solution is the Google. The remain is up to you. There is no other better solution for social network problems other than getting familiar with them by keep working with them.

Wednesday, November 7, 2012

Writing a Custom Mediator for WSO2 ESB - Part 1

Not another "How to Write a Class Mediator"

This blog post discusses how to write a genuine/real Mediator for WSO2 ESB. This is not another article on writing a Class Mediator based on the content from Oxygen Tank articles,
  1. Writing a Mediator in WSO2 ESB - Part 1 and
  2. Writing a Mediator in WSO2 ESB - Part 2 .
Although the above mentioned content is very popular in web, I could not find any article describing how to write a real ESB mediator for WSO2 ESB. This post describes how to create a real ESB mediator.

Difference between a genuine/real mediator vs a Class mediator

In WSO2 ESB you can find mediators like Log Mediator, Clone Mediator, Cache Mediator, Property Mediator and etc. Class mediator is a similar mediator comes ready with the WSO2 ESB. Class mediator is a special mediator that provides an API to a novel programmer to implement his/her custom code as a mediator in side the WSO2 ESB. Above mentioned articles describes how to create a mediator using a Class mediator. But, a Class mediator may not give you the full power of a WSO2 ESB mediator. It will not be shown in the mediator menu that contains the other mediators and will not be able to easily configurable using the UI as other first class citizen mediators. Class mediators cannot extract parameters from the XML exists in the mediator XML as a first class mediator. There may be some other restrictions as well that I have not gone through.

Why this post is important ?

So if you are really interested on creating your own mediator with all the privileges consumed by other mediators in the ESB, you have to create your own mediator as described in this post. I am going to explain the knowledge I gathered while I was designing and implementing the BAM Mediator. I referred the implementation of Smooks Mediator as a reference to a custom mediator. You too can follow either Smooks Mediator or BAM Mediator as the reference mediator if required. The reason is that the implementation of UI bundles and backend bundles are implemented in different places in other available mediators. In those mediators, although the UI components are implemented as WSO2 components, their backends are located inside the dependencies -> Synapse location.

Code and Background

Start Coding

First you have to checkout the WSO2 Carbon source code from the trunk/branch/tag as required. Then you have to build it with Maven 3. Now you can add your custom mediator as a Carbon Component into the correct location. In my case this is the location for the BAM Mediator. (i.e. : BAM Mediator is located in here and Smooks Mediator located in here.) The advantage of using this location is that you can inherit all the required Mevan dependencies from the parents. From here onward for explanation purpose I will use BAM mediator as the example mediator.

Code Locations

Basically you can create the mediator component in /components/mediators/ and you can include all the UI bundles and backend bundles inside your mediator directory /components/mediators/bam. Then you have to go to the Carbon mediators feature in /features/mediators/ and create the mediator feature as /features/mediators/bam-mediator/ in a suitable feature name. Then you can build the p2-repo feature of your feature by adding your feature into the pom.xml in /features/repository/ and building the p2-repo.

Pre-requisite Knowledge

Before you go through this blog you need to have a knowledge on how to work with WSO2 Carbon framework. Basically you need to know how to create a Carbon Component, create a Carbon feature and install a feature to a WSO2 Carbon server. This webinar will be a useful one for learning.
And also being familiar with Apache Mevan 3 and OSGI is required. No need to say about Java :) . It is a must.

Writing the Mediator

Bundles Used

Let's start to create the mediator. First you need to know the usage of UI bundles and backend bundles in a mediator. Mainly there should be at least a one main UI bundle and a one main backend bundle to build a mediator component.

  • Main UI bundle - Adds the UI functionality to be used in the Design Sequence view as shown below. In BAM mediator org.wso2.carbon.mediator.bam.ui is the main UI bundle.

Shows the mediator in the mediator menu

Mediator configuration is allowed via UI under the mediator menu

  • Main backend bundle - Is responsible for all the mediation related backend processing. In BAM mediator the main backend bundle is org.wso2.carbon.mediator.bam .
There can be more UI bundles (e.g. : org.wso2.carbon.mediator.bam.config.ui) and backend bundles (e.g. : org.wso2.carbon.mediator.bam.config) created for helping the main bundles.

Structure of Main Bundles

As WSO2 ESB is allowing the programmer to add their custom mediator as pluggable components to the ESB, most of the UI functionality and mediator functionality required to interact with the rest of the ESB is made transparent to the programmer. In other words the programmer have to program only what he/she really wants from the mediator but not how to plug the component into the ESB. This is one of a sign of the good architecture of WSO2 ESB. It is intelligent enough to identify the Java class by its name and location in the component and refer them appropriately in the ESB. The programmer only need to implement the classes and the rest will be done by the ESB internally. Due to that reason, the user does not have to (and should not) implement a Service Stub to access the main backend bundle from the main UI bundle.
Below it is given the structure of the mediator component (BAM mediator is used as the example) in version, 4.0.3. (Only the relevant directories and files are mentioned) Note that the version of UI component used here is 4.0.1.


For purpose of selecting text, the above structure is given as text below.


.
├── org.wso2.carbon.mediator.bam
│   └── 4.0.3
│       ├── pom.xml
│       └── src
│           └── main
│               ├── java
│               │   └── org
│               │       └── wso2
│               │           └── carbon
│               │               └── mediator
│               │                   └── bam
│               │                       ├── BamMediator.java
│               │                       └── xml
│               │                           ├── BamMediatorFactory.java
│               │                           └── BamMediatorSerializer.java
│               └── resources
│                   └── META-INF
│                       └── services
│                           ├── org.apache.synapse.config.xml.MediatorFactory
│                           └── org.apache.synapse.config.xml.MediatorSerializer
├── org.wso2.carbon.mediator.bam.ui
│   └── 4.0.1
│       ├── pom.xml
│       └── src
│           └── main
│               ├── java
│               │   └── org
│               │       └── wso2
│               │           └── carbon
│               │               └── mediator
│               │                   └── bam
│               │                       └── ui
│               │                           ├── BamMediatorActivator.java
│               │                           ├── BamMediator.java
│               │                           └── BamMediatorService.java
│               └── resources
│                   ├── org
│                   │   └── wso2
│                   │       └── carbon
│                   │           └── mediator
│                   │               └── bam
│                   │                   └── ui
│                   │                       └── i18n
│                   │                           ├── JSResources.properties
│                   │                           └── Resources.properties
│                   └── web
│                       └── bam-mediator
│                           ├── docs
│                           │   ├── images
│                           │   └── userguide.html
│                           ├── edit-mediator.jsp
│                           ├── images
│                           ├── js
│                           └── update-mediator.jsp
└── pom.xml

As the post is going to continue further more let's discuss further on this topic in Part 2.