Sunday, March 31, 2013

Some useful OSGI commands to dig in to issues with deployed bundles deployed in WSO2 products

WSO2 Products developed on top of the core WSO2 Carbon platform.WSO2 Carbon is a componentized Service Oriented Platform(SOA) which is built on OSGI framework,which defines a dynamic component system for Java.Bundle is the unit of modularization in OSGI. 
If I described on how a WSO2 product is created ,first there are a set of components introduced and implemented as OSGI bundles.You can find such developed set of components from here.Then we group a set of components as a feature.And there are such pre-defined features which can be found from here.Then with selecting a relevant set of features,the product have been built.For example this pom.xml under the svn location contains the features set used by the product WSO2 API Manager product.And most importantly,one more advantage of this approach is at later time,product can be customize by adding more  features from wso2 feature manager at runtime.

The main focus of this blog post is to guide on some OSGi level commands that would help to identify issues,when a user tries to deploy an OSGI bundle into a WSO2 product. Most common error the developers are facing,is CNF [Class Not Found] error-Though the OSGI bundle deployed to product,the classes exposing from that particular bundle is not available to OSGI runtime and thus CNF will be thrown.

For such instances,following steps will help you to identify the root-cause of the issue. 
  1. First start the server with  enabling OSGI console available- ./ -DosgiConsole
  2. Then list the available bundles of the server by trying the OSGI command  -  "ss package_name_of_bundle". For get list of commands try the command 'help'.
  3. You'll notice particular bundle will be in 'INSTALLED' state according to OSGI life-cycle.[Not in 'ACTIVE' state]
  4. Try diagnosing the particular bundle with the command "diag bundle_id" [Here bundle_id is the id retrieved for the bundle from above 2nd step]
  5. Once you tried,above you'll see about the un-satisfied  constraints on the specific bundle.In other word,that particular bundle has not become as an active bundle,due to an unsatisfied dependency which is referring from the bundle.
  6. Most of the time,the unsatisfied constraint is a dependency which is imported by the spefic bundle,but from no where else that dependency has export to OSGI runtime,thus unable to find that dependency available in runtime to import and use with the bundle.You can check this by the command 'p packageNameOfUnsatisfiedDependency'.This command will list  the places where the dependency imported and exported.
  7. If the result of above 6,is like no entry about exported places,then we need to add that dependency to OSGI runtime by exporting it from same bundle or from a separate bundle. Or if the package name of that dependency is available as a public JDK package,then you can export it via System bundle by adding an entry for the package name of the dependency to launch.ini file [which can be found from {Product_Home}/repository/conf/etc]

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