[WSO2 ESB] XSLT mediator : Writing a simple style sheet

The XSLT Mediator of WSO2 ESB applies a specified XSLT transformation to a selected element of the current message payload. In this post i am going to write a simple XSLT style sheet which will read values from the current XML payload inside ESB using XPath and populate them into style sheet to create a new or different payload.

Below is our original XML payload.

We will be passing this payload into XSLT mediator with specifying a certain drink name as a parameter to the style sheet. For e.g i am passing drink name as 'Coffee'. At the style sheet it will traverse through incoming payload and find the <lunch> elements which contains 'Coffee' as drink name. If matches found we add the prices of those elements under a new <Payment> element. So when we come out of XSLT mediator the payload will be now changed to the <Payment> entry where it contains drinkPrices of matching elements.

The style sheet 'discountPayment.xsl' is like this.

<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:fn="http://www.w3.org/2005/02/xpath-functions" xmlns:m0="http://services.samples" version="2.0" exclude-result-prefixes="m0 fn">
        <xsl:output method="xml" omit-xml-declaration="yes" indent="yes"/>
        <xsl:param name="drink_name"/>
        <xsl:template match="/">
            <Payment>
                <xsl:for-each select="//Order/lunch[contains(drinkName, $drink_name)]">
                    <discount>
                        <xsl:value-of select="drinkPrice"/>
                    </discount>
                </xsl:for-each>
            </Payment>
        </xsl:template>
</xsl:stylesheet>

Add this style sheet into local-entries of ESB and it can be referred from XSLT mediator as this.

After coming out from XSLT mediator now our current message payload is changed to below.

[WSO2 ESB] Using [resource] attribute for [xsd:import] elements in a scheme file with Validate Mediator

The Validate Mediator in WSO2 ESB is used for schema validation of messages. Then this message is validated against the schema specified.

When we use validate mediator against a schema that schema file itself can contain some other schema references under <xsd:import> elements like below.

If our schema file is like this, in this scenario validate mediator tries to map and find the internal schemas which are defined in <xsd:import> elements. If these cannot be found, ESB will log an error saying that "The resource "{resource_file_name} can not be located"

Therefore in order to use these schema files with validate mediator follow the steps given below.

1. First add all the xsd files as local entries to ESB. These is no relative paths or nested folders supported so the xsd files has to be in local-entries folder itself. However if you put the schemas into registry nested folders are supported.

2. In the validate mediator there is an attribute called <resource>. Use this option to tell the validate mediator on where to find the files to import as below. Make sure ‘location’ and ‘schemaLocation’ entries has the same file name in order to map those correctly. Then the 'key' attribute is used to specify the current location of this schema file as shown in the given exmaple.

If you have added the schema files as registry entries, and when there are relative paths mentioned in parent schema, validate mediator can be used in  the following manner.

WSO2 Message Broker 2.2.0 - An Overview of Newest WSO2 MB Release

After months of hard work we, WSO2 Message Broker team finally completed and released the version 2.2.0 of WSO2 MB, with several community demanded new features and improvements.

The release was initially planned to be go out with two main features namely Dead Letter Channel and Publisher Flow Control. However as the time goes we were able to introduce several more features listed as Cassandra and Zookeeper Profiles support with MB, Message Selectors and Dynamic Queue Support as well as improved SSL and Failover support and a lot more. Below is a quick overview of the newly released WSO2 MB 2.2.0 version. 

The complete information can be found in MB 2.2.0 official documentation which describes each of below feature in detail.

WS02 MB 2.2.0 New Admin Console

What comes new ???

First let's download WSO2 MB 2.2.0 version to experience the new features. Now we are ready go through the list  :)

๏ Dead Letter Channel implementation

The Dead Letter Channel (DLC) is specifically designed to persist messages that are faulty or rejected by the message receivers, providing you with a choice on whether to delete, retrieve or reroute the messages from the DLC. If the subscriber rejected the message, did not ack the sever within a configured time or could not receive message due to connection fail first MB erver will try to resend the message.After doing this for a maximum number of configured times  the message will be routed to DLC.

A user can perform following actions on DLC messages

• Delete (discard mal-formatted message)
• Restore message to the original queue 
• Re-route the message to any other existing queue in MB cluster

๏ Publisher Flow control implementation

Flow control ensures that the rate at which messages are transmitted from the publisher to the receiver is controlled. Back-pressure is exerted when the defined global memory threshold or message count threshold per connection is exceeded. At this point, message acceptance is blocked until the sender is notified of memory recovery.  If the memory is not recovered within a specified time interval 'qpid.flow_control_wait_failure' which is by default 120s (2 mins), all currently publishing clients will be disconnected. But the subscriber clients will be able to continue.

The users are able to increase/decrease this wait time as needed by setting system property 'qpid.flow_control_wait_failure' at client-side. This value is 'long' type.

WSO2 MB 2.2.0 comes with following flow control mechanisms.
1. Throttling based on global memory threshold
2. Throttling based on message count per connection

๏ MB profile support for Cassandra and Zookeeper

With the previous MB releases it was required to download Cassandra and Zookeeper from external sites and point MB to be run with those. From 2.2.0 onwards this is no longer needed and you can start WSO2 MB purely as a Apache Cassandra server. All configurations files of Cassandra are there plus the port is configurable with an offset. The logs related to Cassandra are written to wso2carbon.log file as well as we have introduced a new log file specially for Cassandra system logs, as <MB_HOME>/repository/logs/cassandra_system.log file. Cassandra tools such as nodetool,cassandra-cli scripts are also packed inside MB. Also now you can start WSO2 MB purely as a Apache Zookeeper server. Hence in order to create a complete message broker cluster the users only need a WSO2 MB distribution.

๏ JMS message selectors support

Message selectors allow you to filter specific messages using a selector string. The message consumer will then receive only messages whose headers and properties match the selector. There are different patterns that can be used in selector strings, and the broker (JMS provider) filters messages according to that query. It is not possible for a message selector to filter messages on the basis of the content of the message body.

๏ Queue/Topic Permission model 

The role permission list is modified now the admin can explicitly set the each permissions like create queue/browse queue etc. inside a role. Therefore now when you create a queue/topic it can be selected whether this user can publish/subscribe to the created queue or topic.

WSO2 MB 2.2.0 Permission Model

๏ Dynamic queue support

In previous Message Broker releases users needed to create a subscriber or create the queue from admin console before start publishing messages to that queue and if not messages will be lost. Now this is  improved with dynamic queue support that when the publisher client initiates the queue is created in the broker, even if there are no consumers. The create queue segmant of message publisher would be as follows.

        QueueConnectionFactory connFactory = (QueueConnectionFactory) ctx.lookup(CF_NAME);
        QueueConnection queueConnection = connFactory.createQueueConnection();
        queueConnection.start();
        QueueSession queueSession =
                queueConnection.createQueueSession(false, QueueSession.AUTO_ACKNOWLEDGE);
        // create queue
        Queue queue =  queueSession.createQueue("Queue-MB");
        // create the message producer for queue
        javax.jms.QueueSender queueSender = queueSession.createSender(queue);

๏ Improved SSL support

The wire level connection between client-server of broker can be encrypted using SSL to provide maximum protection where this is supported in both standalone and clustered mode with failover as well. The SSL properies are easily configurable at the client side using AMQP connection url.

๏ Improved logging 

Trace level logs are now separated for easy debugging. In addition there are two more log files have been introduced for Cassandra and Zookeeper profiles named, cassandra_system.log and zookeeper.log file.

๏ Queue/Topics Subscription UI

A new segmant is introdued to WSO2 MB 2.2.0 admin console as shown in above image to view active/inactive queue and topic subscriptions for whole MB cluster. The following details are displayed in the new UI.

• View active topic subscriptions in whole MB cluster 
• View inactive durable topic subscriptions specifically.
• Ability to unsubscribe inactive durable topic subscriptions with UI.

Queue/Topic Subscriptions UI

Apart from these major changes there are a lot of bug fixes and improvements in the new release. It was a great and hard team work for the last few months for all of us ( there are a lot in the team including our QA crew) to finally get the 2.2.0 release out. It is really proud to be a part of my team and we are now gearing up for WSO2 MB 3.0.0 which will be coming out as a complete revamped architecture. Looking forward for 3.0.0 :) :)

[Quick Note] Modifying Git Configurations in Ubuntu and Windows

OS : Ubuntu 13.10 or Windows 7

This is a brief post on how to change default configuration entries for Git.

There might be requirements that you need to change the default username where the commits get written to github, specially if you created a new github account, changed email etc.

Git uses global configuration file called .gitconfig in order to store the global credentials. To change the default user you can simply edit this file.

isha@thinkpad:~$ vim .gitconfig

For Windows this file can be found in file: git/etc/.config location.
I have set the following three properties here.

 1. username: github username of author.
 2. user email: github email address of user.
 3. credential helper: turn on the credential helper so that Git will save your password in memory for some time. By default Git will cache your password for 15 minutes. You can change this by changing --timeout property in the command.

[user]
        name = ishadil
        email = ishadil@github.com
[credential]
        helper = cache --timeout=3600  // i have changed timeout for 1 hour

Other option is doing this using the command prompt as below.

git config --global user.name "ishadil"

git config --global user.email "ishadil@github.com"

git config --global credential.helper 'cache --timeout=3600'

After that use git config --global --list command to verify whether the properties are reset correctly.

git config --global --list

In a similar manner there are lot more configuration entries that can be set into this file. For e.g. let's set a proxy url in to git .config file.

[http]
    proxy = proxy-test.abc.com:8080

WSO2 ESB Performance Round 7.5 is now released ......

As the Enterprise Service Bus 4.8.1 version was out in early February this year WSO2 ESB team has carried out a latest ESB Performance round, which results in that the newly released WSO2 ESB clearly outperforms other ESBs in the current market. The ESB Performance round 7.5 testing was conducted on an Amazon c1.xlarge EC2 instance of a 64-bit instance with 8 cores, 20 ECUs, and 7GB of memory.

The following table and graph show the summary results which is drawn against 'Average TPS Values' per 'Proxy Service' of the performance test. In summary it can be stated that,

• As shown in the graphs below, WSO2 ESB 4.8.1 is the fastest in performance compared to all the other ESBs here, except for the security scenario.

1.


2.



The 'ESB Performance Round 7.5' article in the WSO2 Library provides a comprehensive report of the complete test round. 

Securing a Proxy Service in WSO2 ESB using a Username and passwordDigest (Hashpassword)

In this post i am going to explain how to secure a simple proxy service in WSO2 ESB 4.7.0 to be authenticated with UsernameToken method with using the username and hashpassword.

The HashPassword or NoPassword options are defined with WS-Policy 1.2 specification onwards. Therefore in order to have this feature we need to write a policy file using WS-Policy 1.2 spec.

First let's create a simple pass through proxy and make it secured.

1. Add a new pass through proxy  and specify an endpoint of a running service there. I have used SimpleStockQuoteService which can be run in <ESB_Home>/samples/axis2Server/src/SimpleStockQuoteService. Build the service using 'ant' and start the Axis2 server by,

cd ESB_home/samples/axis2Server $ sh axis2Server.sh 

2. After this go to the list of service in the UI. You will see that 'StockQuoteSecure' service is displayed as "Unsecured". Click on this link and it will redirect to a page where you can enable security to this service. Enable security there and select UsernameToken as the basic authentication mechanism as shown in the image below. After that goto next page and select the user groups who can access this service.

3. Once you finish this, WSO2 ESB admin console will display the service as secured, and we can only invoke this service using https:// endpoint now.

4. Next we need to change a default UsernameToken policy of the service and make it able to validate Hashpasswords. Goto the service dashboard of the secured service by clicking on it. Under the 'Quality of Service Configuration' section 'Policies' will be defined.

5. When you click on 'Policies' link it will be redirected to edit the current policy. Find 'StockQuoteSecureSoap11Binding' tab in here and click on 'Edit Policy' button as shown below.

6. Now let's define our new policy here. Copy the Following policy configuration and replace the existing policy definition with this one.

Save the policy back.

    
        
            
                
                    
                        
                    
                
                
                    
                        
                    
                
                
                    
                        
                    
                
                
            
        
        
            
                
                    
                        
                        
                    
                
            
        
        
            useReqSigCert
	    admin
	    org.wso2.carbon.digestpwd.PWCBHandler
        
    

7. The StockQuoteSecure service is secured now and is configured to use Username and Hashpassword for authentication.

8. As defined in the policy configuration, it uses org.wso2.carbon.digestpwd.PWCBHandler class to validate the user. Here i have written PWCBHandler.java class which can validate the default 'admin' user of WSO2 ESB.  Before trying to invoke the proxy service we need to add this PWCBHandler-1.0.jar client library into <ESB_Home>/repository/components/lib directory. You can download the jar from here.

[ The above sample PWCBHandler class is written to validate the 'admin' user only. According to your requirements you can write a customized PasswordCallBackHandler class which validates a set of registered users etc. in similar manner. ]

9. Now we can invoke the secured service using a Client, and i have used SOAP UI as the sample client here. Create a new SoapUI project by using SimpleStockQuoteService.wsdl file attached here. Then use any of the operations defined in the SimpleStockQuoteService and send a request to oure secured proxy service using SoapUI. Before sending the request enter the following values as Request Properties.

Username: admin

Password: admin

WSS-Password Type: PasswordDigest

WSS Time to Live: 2000

10. Once sent the request there will be a response message  returned from SimpleStockQuoteService which implies that the Usename/Hashpassword combination is authenticated successfully.

Using WSO2 Message Broker with RabbitMQ C# .Net Client

As WSO2 Message Broker supports AMQP (Advanced Message Queuing Protocol) v 0.91 standard, this can be used to provide interoperability between different platforms via AMQP clients written on different languages. This blog post is about how to connect with WSO2 MB 2.1.0 using a C# .Net client and perform Queue/Topic based operations on Message Broker. 

In order to connect with MB first we need to find a C# .Net client library which supports AMQP standards. I have used RabbitMQ .Net client library here for this purpose.

1. How to Publish/Subscribe to Queues via .Net client

 

The following tutorial in WSO2 Library provides a complete guide on how to perform Queue operations  in by connecting to WSO2 MB via the .Net client. Therefore i am not going to repeat it here and let's see how to use manipulate Topics with a C# .Net client.

2. How to Publish/Subscribe to Topics via .Net client

 

The main difference between  connecting to a Topic and a Queue is, by default in WSO2 MB they use two different exchanges in order to connect with Queue and Topics. Therefore if you need to connect to a Queue/Topic, first it needs to be bound to the 'Exchange' in the broker by specifying the exchange name. There are two default exchanges used in WSO2 Message Broker.

• 'amq.direct' : The pre-defined direct exchange, used with Queues
• 'amq.topic'  :  The pre-defined topic exchange, used with Topics

You can still define and create new exchanges if needed, however they need to be first added into <MB_Home>/Repository/conf/advanced/qpid-virtualhosts.xml file under the <exchanges> section as the example below. However it is usually recommended to use the default direct/topic exchanges.

       
    
        
           direct
           carbon.direct
           true
       
       
            topic
            carbon.topic
       
  

Now let's get back to writing our sample code.

I. The following is a sample client code to publish into  a Topic in the broker. The code itself includes self-explanatory comments which describe its functions.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using RabbitMQ.Client;
 
 
namespace MB_Topic_Publisher
 
{
 
    class TopicPublisher
 
    {
        static void Main(string[] args)
 
        {
            TopicPublisher topicPublisher = new TopicPublisher();
            topicPublisher.PublishMessage("Test Message");
            Console.WriteLine("Message Sent..");
            Console.ReadLine();
        }
 
        public void PublishMessage(string message)
 
        {
 
//Setup the connection with the message broker
            ConnectionFactory factory = new ConnectionFactory();
            IProtocol protocol = Protocols.AMQP_0_8_QPID;
            factory.VirtualHost = "/carbon";
            factory.UserName = "admin";
            factory.Password = "admin";
            factory.HostName = "localhost";
            factory.Port = 5672;
            factory.Protocol = protocol;
 
            using (IConnection conn = factory.CreateConnection())
 
            {
                using (IModel ch = conn.CreateModel())
                {
 
// Declare a topic exchange to publish messages, here we have used the default topic exchange of WSO2 MB
                 ch.ExchangeDeclare("amq.topic", "topic");
 
// Publish the message to the exchange, it will send it to the routing key which is our name 'myTopic'.
// The syntax is ch.BasicPublish(exchange_name, topic_name, message_properties,message_body)
                 ch.BasicPublish("amq.topic", "test-topic", null, Encoding.UTF8.GetBytes(message));
 
                }
            }
        }
    }
}



II. Then let's write the sample client code to consume messages from  a Topic in the broker.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using RabbitMQ.Client;
 
namespace MB_TopicClient
 
{
    class TopicConsumer
    {
        static void Main(string[] args)
       {
            TopicConsumer topicConsumer = new TopicConsumer();
            topicConsumer.getMessages();
        }
 
        public void getMessages()
        {
 
//Setup the connection with the message broker
            ConnectionFactory factory = new ConnectionFactory(); 
            IProtocol protocol = Protocols.AMQP_0_8_QPID;
            factory.VirtualHost = "/carbon";
            factory.UserName = "admin";
            factory.Password = "admin";
            factory.HostName = "localhost";
            factory.Port = 5672;
            factory.Protocol = protocol;
 
            using (IConnection conn = factory.CreateConnection())
            {
                using (IModel ch = conn.CreateModel())
 
                {
// Declare a topic exchange to be bound to retrieve messages, here we have used the default topic exchange of WSO2 MB
                    ch.ExchangeDeclare("amq.topic", "topic");
             
// Declare a topic name, here we use a non-durable topic. To make it durable use the 2nd parameter as 'true' 
                    ch.QueueDeclare("test-topic", false, false, false, null);
  
// Bind the Topic in to the exchange
                    ch.QueueBind("test-topic", "amq.topic", "test-topic");
                     
// Declare a consumer which listens on the messages published to 'test-topic' topic, we need to declare an exclusive subscriber, in order to get this work.
// The syntax is BasicConsume(queuename, noAck,consumerTag, noLocal, exclusive, arguments, Consumer)                      
                     
                    QueueingBasicConsumer consumer = new QueueingBasicConsumer(ch);
 
                    ch.BasicConsume("test-topic", false, "1", false, true, null, consumer);
                    while (true)
                    {
                        try
                        {
                            RabbitMQ.Client.Events.BasicDeliverEventArgs e =(RabbitMQ.Client.Events.BasicDeliverEventArgs)consumer.Queue.Dequeue();
                            byte[] body = e.Body;
                            string message = Encoding.UTF8.GetString(body);
                            Console.WriteLine(message);
                            ch.BasicAck(e.DeliveryTag, false);
 
                        }
                        catch (OperationCanceledException e)
                        {
                            Console.WriteLine(e);
                            break;
                        }
                     }
                }
            }
        }
    }
}



3. Download and Running the sample

To run the clients first run the sample Topic Consumer where it will create a new topic subscription for the 'myTopic'. After the when you run the sample Topic Publisher client, the consumer will receive the message published and will display it in the console as "Test Message".

The complete source code along with the RabbitMQ.Client.dll library can be downloaded from here too.

4. A guide to RabbitMQ .Net library API

If you need to learn on how to use the API to customize the sample Publisher and Consumer before using it with WSO2 Message Broker, refer the guides given below. 

• RabbitMQ .Net client v2.8.4 API Guide : find here 
• RabbitMQ .Net client v2.8.4 User Guide : find here