Engwar | Chintana Wilamuna's weblog

CassandraSF 2011

Posted on July 13, 2011 by Chintana

I was at CassandraSF 2011 yesterday and was surprised by the 450 – 500 people showing up for the conference. The community and the momentum behind Cassandra at the moment is exciting. Jonathan Ellis kicked off the conference with his keynote speech where he laid out the progress so far and features that have been planned ahead for the project.

After Jonathan’s keynote, I went for the CloudSandra presentation where they’ve implemented a framework with Brisk. The presentation seem to be intriguing as they’ve developed a multi-tenant REST API for Cassandra. Although the meaning of multi-tenancy seemed to have interpreted differently as I’ve been used to the term. Multi-tenancy as I know it have been used to treat a particular organization (an entity as you will) as a tenant and you can have individual users inside that tenant. I felt the multi-tenancy in CloudSandra meant more like multi-user system. I may be wrong. Their usage of Apigee to play with the REST API was very cool as Apigee provide a neat UI for your REST APIs.

Next was an entertaining talk by Eric Evans. Was quite fun as Eric the guy who helped popularize the term NoSQL and the talk was regarding SQL like query language for Cassandra called CQL! It was mostly about high level info/rationale behind coming up with CQL and the current state and some hints as to how it might evolve in time to come.

After that there was a session about Brisk. An introduction and what Brisk is all about by Jake Luciani.

Then David Strauss did an entertaining talk where he demoed a highly available DNS server written using Cassandra. He showed how data propagetes to 3 machines hosted in 3 geographical areas. Very cool!

During Adrian Cockcroft‘s presentation he described how Netflix is using Cassandra, how they migrated to Cassandra from on Oracle DB. Also plethora of other operation aspects of Cassandra clusters. One point he stressed during the talk was, since they were running exclusively on EC2 nodes they had to take instance termination as a fact of life. So they write apps so that they’re resilient even couple of nodes go down. They also deliberately kill random instances and test if the system function as expected!

As the final session of the day attended the Cassandra internals by Gary Dusbabek walked the audience through the Cassandra code base. How everything is wired together and where critical components are at.

Posted in cassandra, cassandrasf2011, nosql | Leave a comment

Maven setup for Axis2 service development

Posted on August 13, 2010 by Chintana

There are many resources on the Net giving how to write an Axis2 service. And of course internals of Axis2 itself. This is a simple guide that aims to provide info on howto setup the build environment so that you can get a deployable artifact of an Axis2 service.

For the most part you’ll be starting after generating Java code against a given WSDL. Generate code with the same version of Axis2 that you’ll be using to deploy this service. Evil things will happen otherwise.
After this, you can create a skeleton maven project using the maven quickstart archetype.
```
$ mvn archetype:generate -DgroupId=com.example.myproject -DartifactId=mysuper-service -DpackageName=org.example.myproject -Dversion=1.0-SNAPSHOT
```
In the next screen you just have to press enter the selected archetype is the quickstart archetype. Then you can select an appropriate version number for the project followed by the package name. Now you should have a skeleton maven project where you can run mvn clean install and it’ll successfully build it.
Now you can copy the generated classes to mysuper-service/src/main/java and start developing your services.

To generate an Axis2 .aar file you have to tell maven to build a .aar file using the maven aar plugin.

<build>
    <plugins>
        <plugin>
            <groupId>org.apache.axis2</groupId>
            <artifactId>axis2-aar-maven-plugin</artifactId>
            <version>1.4</version>
            <extensions>true</extensions>
            <configuration>
                <servicesXmlFile>${basedir}/resources/services.xml</servicesXmlFile>
                <wsdlFile>${basedir}/resources/test.wsdl</wsdlFile>
                <fileSets>
                    <fileSet>
                        <directory>${basedir}/lib</directory>
                        <outputDirectory>lib</outputDirectory>
                        <includes>
                            <include>*.jar</include>
                        </includes>
                    </fileSet>
                </fileSets>
            </configuration>
        </plugin>
    </plugins>
</build>

Here, I’ve included a lib folder as well, which contains 3rd party .jar files that’s not available on a maven repo. Once you’ve added the lib folder containing a set of .jar files you can add the dependency later using something like,

<dependency>
            <groupId>com.example.myjar</groupId>
            <artifactId>jarfile</artifactId>
            <version>1.0</version>
            <scope>system</scope>
            <systemPath>${basedir}/lib/the-other-awesome-project.jar</systemPath>
</dependency>

When you’re specifying a 3rd party JAR dependency even though the actual JAR file might not contain a version number, you have to include something in the <version> element. Otherwise maven will not work correctly.

Now, when you type $ mvn clean install you should have a .aar file in the target folder. You can upload this to Axis2 and your services will be deployed in a few seconds.

Building within the IDE

An IntelliJ IDEA project file for your project can be easily generated with $ mvn idea:idea. But if you project use maven, you have to install IntelliJ IDEA maven 2 integration plugin. This can be done using the IDEA plugin browser. Even after adding my root pom.xml to Maven-2 Build in IDEA, I was only able to compile all the classes. I couldn’t get any maven plugin goals to be executed. So, Ctrl+F9 still doesn’t generate the .aar file.

As it turns out, you need to install Maven Reloaded plugin to be able to execute maven plugin goals. After installing this, the execution process dies with exit status 1 without any helpful remarks.

Posted in axis2, maven | Leave a comment

Codegen and runtime Axis2 versions

Posted on August 13, 2010 by Chintana

I was bitten by this error a couple of times I thought of blogging it for my own reference. It’s important to remember that when you’re generating code against some WSDL, you have to use the same version of Axis2 that you’re going to deploy this service on. So, when you’re running WSDL2Java.sh that should come from a Axis2 distribution that is used in the application server that your service will get deployed. Otherwise, if the Axis2 versions differ you’ll see the following error message.

java.lang.AbstractMethodError
	at org.apache.axis2.databinding.ADBDataSource.serialize(ADBDataSource.java:90)
	at org.apache.axiom.om.impl.llom.OMSourcedElementImpl.internalSerialize(OMSourcedElementImpl.java:691)
	at org.apache.axiom.om.impl.llom.OMElementImpl.internalSerialize(OMElementImpl.java:965)
	at org.apache.axiom.soap.impl.llom.SOAPEnvelopeImpl.serializeInternally(SOAPEnvelopeImpl.java:283)
	at org.apache.axiom.soap.impl.llom.SOAPEnvelopeImpl.internalSerialize(SOAPEnvelopeImpl.java:245)
	at org.apache.axiom.om.impl.llom.OMSerializableImpl.serializeAndConsume(OMSerializableImpl.java:193)
	at org.apache.axis2.transport.http.SOAPMessageFormatter.writeTo(SOAPMessageFormatter.java:79)
	at org.apache.axis2.transport.http.CommonsHTTPTransportSender.sendUsingOutputStream(CommonsHTTPTransportSender.java:361)
	at org.apache.axis2.transport.http.CommonsHTTPTransportSender.invoke(CommonsHTTPTransportSender.java:238)
	at org.apache.axis2.engine.AxisEngine.send(AxisEngine.java:443)
	at org.apache.axis2.receivers.AbstractInOutMessageReceiver.invokeBusinessLogic(AbstractInOutMessageReceiver.java:43)
	at org.apache.axis2.receivers.AbstractMessageReceiver.receive(AbstractMessageReceiver.java:114)
	at org.apache.axis2.engine.AxisEngine.receive(AxisEngine.java:178)
	at org.apache.axis2.transport.http.HTTPTransportUtils.processHTTPPostRequest(HTTPTransportUtils.java:173)
	at org.apache.axis2.transport.http.AxisServlet.doPost(AxisServlet.java:144)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:709)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
	at org.eclipse.equinox.http.servlet.internal.ServletRegistration.handleRequest(ServletRegistration.java:90)
	at org.eclipse.equinox.http.servlet.internal.ProxyServlet.processAlias(ProxyServlet.java:111)
	at org.eclipse.equinox.http.servlet.internal.ProxyServlet.service(ProxyServlet.java:67)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
	at org.wso2.carbon.bridge.BridgeServlet.service(BridgeServlet.java:154)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:269)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:210)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:174)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:117)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:108)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:151)
	at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:870)
	at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:665)
	at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:528)
	at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:81)
	at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:685)
	at java.lang.Thread.run(Thread.java:619)

Posted in Uncategorized | 3 Comments