Showing posts with label brokers. Show all posts
Showing posts with label brokers. Show all posts

Sunday, July 28, 2013

Writing a Node.js Client to Send/Receive messages with WSO2 Messge Broker

WSO2 Message Broker supports AMQP protocol 0-9-1. If you need to use Node.js client to publish/subscribe to Message Broker this can be done with using any compatible Node.js AMQP 0-9-1 Client Library. Some of the examples i found are,
  1. amqp.node : https://github.com/squaremo/amqp.node
  2. node-amqp : https://github.com/postwait/node-amqp
First of all we need to install Node.js if we haven't done it yet. The following page explains how to install Node.js in Ubuntu.

$ sudo apt-get install python-software-properties python g++ make 
$ sudo add-apt-repository ppa:chris-lea/node.js 
$ sudo apt-get update $ sudo apt-get install nodejs

Then add 'amqplib' module to get enable the functions in 'node.amqp' library.

$ npm install amqplib

The following sample code, written using amqp.node library can be used now as a NodeJS client to publish or receive messages from WSO2 Message Broker. You have to use the format amqp://{username}:{password}@{hostname}:{port} to establish a connection with Message Broker. All messages will be sent as byte messages but can be received as text.
'amqp.node' library provide a rich API which can be used to other Queue operations MB too.
  
A Sample Node.js Queue Publisher for WSO2 MB
    
    var queuename = 'MyQueue'; 

    var openConn = require('amqplib').connect('amqp://admin:admin@localhost:5672'); 

    // amqp://{username}:{password}@{hostname}:{port} is default AMQP connection URL of WSO2 MB 

    openConn.then(function(conn) { 

    var ok = conn.createChannel(); 

    ok = ok.then(function(channel) 

    { channel.assertQueue(queuename); 

    channel.sendToQueue(queuename, new Buffer('New Message')); }); 

    return ok; 

    }).then(null, console.warn);  

A Sample Node.js Queue Consumer for WSO2 MB
var queuename = 'MyQueue'; 

    var openConn = require('amqplib').connect('amqp://admin:admin@localhost:5672'); 

    // amqp://{username}:{password}@{hostname}:{port} is default AMQP connection URL of WSO2 MB 

    openConn.then(function(conn) { 

    var ok = conn.createChannel(); 

    ok = ok.then(function(channel) { 

           channel.assertQueue(queuename); 

    channel.consume(queuename, function(msg) { 

    console.log(msg.content.toString()); 

    channel.ack(msg); }); 

    }); 

    return ok; 

    }).then(null, console.warn);

Monday, July 15, 2013

Creating an OSGi Bundle out of a Third Party Library for Using as WSO2 Product Dependency

WSO2 platform supports a modular based architecture where third party libraries which are used in WSO2 products are exposed into the environment as OSGi bundles. This blog post is about how to OSGify a third party library, to be used as a dependency inside WSO2 MB.

We have recently used 'Disruptor', a high performance inter-thread messaging library  as a dependency in WSO2 Message Broker for improving the performance by using disruptor based message writing operations into Cassandra storage. When doing this it is first needed to create an OSGi bundle out of 'Disruptor' library, so it can be referred in the runtime when Message Broker is running.

As common to all OSGi bundle generations, first you need to have a manifest.mf file which describes the bundle information, version info, which packages needed to be imported/exported etc. However as it is not easy to write this file correctly by hand we use maven-bundle-plugin in order to get this done. This process is common to any third party dependency and you can follow the same process in building an osgi bundle for any of them.

1. First let's create a directory named 'disruptor' inside <WSO2_Carbon_Source>/platform/dependencies/orbit/ directory. As we have used Disruptor 2.10.4 version i created a new package called 2.10.4-wso2v1 inside disruptor directory. (This is the common notation across the platform <LibraryVersion>-wso2v<VersionNumber>when naming the versions of the dependencies.)

2. Add a new maven build file (pom.xml) inside package 2.10.4-wso2v1.

3. Now let's add the required details which needs to generate the OSGi bundle into this file. This pom file can be used as a sample template by replacing the required entries when adding another dependency.

<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 ">http://maven.apache.org/maven-v4_0_0.xsd">

<parent>
   <groupId>org.wso2.carbon</groupId>
   <artifactId>carbon-dependents</artifactId>
   <version>4.1.0</version>
   <relativePath>../../../pom.xml</relativePath>
</parent>

<modelVersion>4.0.0</modelVersion>
<groupId>com.googlecode.disruptor.wso2</groupId>
<artifactId>disruptor</artifactId>
<packaging>bundle</packaging>
<name>WSO2 Carbon - Orbit - disruptor</name>
<version>2.10.4-wso2v1</version>
<description>This bundle exports packages from disruptor jar files</description>
<url>http://wso2.org</url>

<dependencies>
   <dependency>
      <groupId>com.googlecode.disruptor</groupId>
      <artifactId>disruptor</artifactId>
      <version>2.10.4</version>
      <optional>true</optional>
   </dependency>
</dependencies>

<build>
     <plugins>
            <plugin>
                 <groupId>org.apache.felix</groupId>
                 <artifactId>maven-bundle-plugin</artifactId>
                 <version>1.4.0</version>
                 <extensions>true</extensions>
                 <configuration>
                      <instructions>
                        <Bundle-SymbolicName>${project.artifactId}</Bundle-SymbolicName>
                        <Bundle-Name>${project.artifactId}</Bundle-Name>
                        <Export-Package>
                                com.lmax.disruptor.*;version=2.10.4,
                         </Export-Package>
                        <Import-Package>
                                !sun.misc,
                                *
                        </Import-Package>
                      </instructions>
                </configuration>
            </plugin>
     </plugins>
</build>

<!--<repositories>
    <repository>
       <snapshots>
          <enabled>true</enabled>
          <updatePolicy>daily</updatePolicy>
          <checksumPolicy>ignore</checksumPolicy>
    </snapshots>
    <id>wso2-maven2-snapshot-repository</id>
    <name>WSO2 Maven2 Snapshot Repository</name>
    <url>http://dist.wso2.org/snapshots/maven2/</url>
    <layout>default</layout>
  </repository>
</repositories>-->

<properties>
     <disruptor.build.version>2.10.4</disruptor.build.version>
     <disruptor.version>${disruptor.build.version}-wso2v1</disruptor.version>
 <disruptor.orbit.version>${disruptor.build.version}.wso2v1</disruptor.orbit.version>
</properties>
</project>


Let's go trough the important entries in the file.

<dependencies>
<dependency>
<groupId>com.googlecode.disruptor</groupId>
<artifactId>disruptor</artifactId>
<version>2.10.4</version>
<optional>true</optional>
</dependency>
</dependencies>


As we are using external library in the OSGi bundle we need to add this as a maven dependency entry for the bundle. You can find maven dependency entries of lot of libraries in here.

<build>
<plugins>
<plugin>
<groupId>org.apache.felix</groupId>
<artifactId>maven-bundle-plugin</artifactId>
<version>1.4.0</version>
<extensions>true</extensions>
<configuration>
<instructions>
<Bundle-SymbolicName>${project.artifactId}</Bundle-SymbolicName>
<Bundle-Name>${project.artifactId}</Bundle-Name>
<Export-Package>
             com.lmax.disruptor.*;version=2.10.4,
</Export-Package>
<Import-Package>
             !sun.misc,
             *
</Import-Package>
</instructions>
</configuration>
</plugin>
</plugins>
</build>


This is how we use maven-bundle-plugin to generate the disruptor osgi bundle. The Export-Package, Import-Package and DynamicImport-Package tags are used to control the exposure of certain packages to other bundles. With <Export-Package> tag it will find the defined project classes or dependencies, and they will be copied to the osgi bundle. With using <Import-Package> here, we can import the extra classes that have been referred from our osgi bundle. By keeping * as the value here by default it imports all the reference classes that needs for OSGi bundle generation. However when using default value here for 'disruptor bundle' i encountered the following error.

org.osgi.framework.BundleException: The bundle could not be resolved. Reason: Missing Constraint: Import-Package: sun.misc; version="0.0.0"

So I added the entry '!sun.misc' to resolve this issue and it seems as the sun.misc package is already there to be referred by the osgi framework, we need to tell that it is not needed to explicitly import it in this case. This is a 'Disruptor' bundle specific entry and you don't have to add the same configuration in each bundle you create. However if the bundle's classes use sun.misc package, this setting might be useful in resolving similar errors.


4. That's it! Save the pom file and build it with maven ( WSO2 projects use Maven3). You will see that in the <WSO2_Carbon_Source>/platform/dependencies/orbit/disruptor/2.10.4-wso2v1/target folder the newly created osgi bundle 'disruptor-2.10.4-wso2v1.jar' is present.

If you see the manifest.mf file of the new bundle it will be as follows.

Manifest-Version: 1.0
Export-Package: com.lmax.disruptor.collections;version="2.10.4",com.lm
ax.disruptor;uses:="com.lmax.disruptor.util";version="2.10.4",com.lma
x.disruptor.dsl;uses:="com.lmax.disruptor,com.lmax.disruptor.util";ve
rsion="2.10.4",com.lmax.disruptor.util;uses:="com.lmax.disruptor";ver
sion="2.10.4"
Ignore-Package: sun.misc
Built-By: <your_host_name>
Tool: Bnd-0.0.238
Bundle-Name: disruptor
Created-By: Apache Maven Bundle Plugin
Bundle-Version: 2.10.4.wso2v1
Build-Jdk: 1.6.0_30
Bnd-LastModified: 1373904351577
Bundle-ManifestVersion: 2
Bundle-Description: This bundle exports packages from disruptor jar fi
les
Bundle-SymbolicName: disruptor
Import-Package: com.lmax.disruptor;version="2.10.4",com.lmax.disruptor
.collections;version="2.10.4",com.lmax.disruptor.dsl;version="2.10.4"
,com.lmax.disruptor.util;version="2.10.4"



To know more about creating OSGi bundles with maven-bundle-plugin, you can read the following article in WSO2 Library.


[1]. http://wso2.com/library/tutorials/develop-osgi-bundles-using-maven-bundle-plugin

Wednesday, May 29, 2013

Providing Queue browing, message sending and purging features in WSO2 MB 2.1.0

WSO2 MB is a Message Broker which enables applications to exchange communications asynchronously or publish messages for timely access by many subscribers. For the past versions of WSO2 MB there was no support for sending sample messages from the admin console or viewing the messages in a queue. hence in WSO2 MB 2.1.0 onwards, we have added this functionality into the broker.

Therefore it is now possible to,
  1.  Send sample text messages to a queue in WSO2 MB
  2.  Browse the content in a queue using MB admin console
  3.  Purge a queue via admin console and make it empty in WSO2 MB as of the expectation of many users.

The following are some of the snapshots from the new view of the MB admin console.  The 2.1.0 version is not yet released for public but will be releasing by end of this month.

1. New view of the 'Queue Menu'



2. New Queue Browser in WSO2 MB


3. New Message Sending UI in MB


4. New Queue purging option in MB


More details on the new features can be found in MB 2.1.0 documentation once it is released.