Friday, April 26, 2013

Multiple Profiles and Shared Bundles With Eclipse P2 : Case Study

WSO2 Carbon is an OSGi based server framework. Number of WSO2 middleware products use Carbon as their base platform. Carbon make use of Eclipse Equinox as its OSGi framework implementation and use Eclipse P2 as its provisioning framework.

Problem Description

Some of the Carbon products has their own deployment patterns during actual production deployments. However to give a smooth evaluation experience the same product is available as a 'ready to go' all in one zip distribution. For an example, WSO2 Business Activity Monitor(BAM) allows enterprises to batch process their collected enterprise data and present it by means of human readable graphs/etc. A real production deployment includes, three main parts.

Figure 1

1. Receiver component responsible for receiving the events
2. Storage and Analyzer will analyze the stored data in batch mode.
3. presentation component will present the processed data by means of dashboard elements.

Even though these components are distinct by their functionality and by their deployment, they are all part of an one product. The first experience of the middleware developer should be seamless, means Business Activity monitor product should include all these components. However having all the components in the product resolves to a larger memory footprint during the run-time. During an actual deployment users have to deploy three seperate BAM instances even though they are interested only in one functionality of the product at a given time - they can't deploy only the receiver bit of BAM.

All of WSO2's Carbon based middleware products are available in the cloud as a multitenanted PAAS offering. This resolves to a atleast one product instance from each of the product types (Enterprise Service Bus, Application Server,etc). If we take per product distribution size to be ~100MB, then ten product instances will resolve in to 1GB. However we want to make our cloud offering available to users as a downloadable archive. This will enable them to easily download/setup their own private PAAS and evalute it - means total distribution size matters.

Solution 1 : Handling multiple profiles

Figure 2

There is one important aspect in the above described BAM scenario. All the different deployment entities can share the same configuration. Being differnt component of BAM server, the configuration requirement of the three different components are more or less the same. If we can selectively activate some of these functionalities using a switch mechanism, that would do the trick. The Eclipse P2 has a concept called profiles. Once you provision your OSGi application using P2, the application get assigned a profile. During the server startup, only the bundles that were provisioned under a particular profile get started. We created seperate profiles for each BAM component, namely receiver, analyzer and dashboard. During the server start-up user can select the profile by means of a system property. The default profile contains functionality of all of the BAM components just like good old days. The notion of profile is a logical partition that works with server provisioning framework. Each of these profiles share the same set of bundles in a shared repository, hence there is no increase in the distribution size.

Solution 2 : Shared bundle pool during run-time


The solution for the second problem, can be addressed using P2 profiles and shared bundle pools as well. However there is a suttle difference in the approach. Unlike the BAM use case, each of these different products have their own configuration area and data/persistance locations. We can tackle this requirement by completely removing the bundle pool location from the product distribution and placing it outside of all products. Each product will have their own configuration/distribution area and all the products will point to the same bundle location, hence distribution size will be much much less. The use case demands runtime isolation (running two or more products parallely using the same bundle location) and we can successfully achieve the same using P2 profiles and bundle pooling.


P2 bundle pooling functionality coupled with roaming (the ability to move your provisioned application from your original location - relies on relative paths) seems to be broken. However with the help from P2 dev-list we figured out a workaround.

wso2 BAM product presentation slides

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