WebSphere eXtreme Scale Best Practices for Operation and Management

72 WebSphere eXtreme Scale Best Practices for Operation and Management

The grid containers initialize the object grids that are defined in the configuration files upon

start-up of the Java EE application that contains the module. This method makes it easier to

manage the WebSphere eXtreme Scale run time without relying on scripts to launch the grid

containers. For embedded environments, if you want the configuration files to be external to

your modules and .ear or .war files, you can use a technique where you refer to the two

configuration files by defining two URLs each with a well-known Java Naming and Directory

Interface (JNDI) name. This way, the files remain outside any compiled unit and can be more

easily edited by operations as the need arises.

5.1.2 Client XML configuration

An WebSphere eXtreme Scale client also has an ObjectGrid descriptor configuration. The

descriptor initially is the same as the descriptor XML that you gave to the containers to which

the client connects. The client run time is passed this descriptor configuration transparently at

the time that it connects and gets the ObjectGrid reference. In certain cases, it might be

necessary to override parts of the object grid configuration on the client. For example, a

loader plug-in might make sense on the server but the Loader class probably does not even

exist on the client. The specifics of evictors might differ on the client from the server. You

might want to turn off certain features, such as the near cache.

Overriding plug-ins

The following plug-ins and attributes can be overridden in the client ObjectGrid descriptor

XML file:

򐂰 ObjectGrid plug-ins:

– TransactionCallback plug-in

– ObjectGridEventListener plug-in

– Security-related plug-ins

򐂰 BackingMap plug-ins:

– ObjectTransformer plug-in (for efficient serialization)

– Evictor plug-in

Download material: For an example of WebSphere eXtreme Scale code that allows you

to start a WebSphere Application Server application server as an WebSphere eXtreme

Scale container using your XML files but with those files external to any compiled .ear or

.war file, see the WAS+XS_ExternalXML_Package.zip file in the additional materials that are

available for this book. For information about downloading this material, see Appendix B,

“Additional material” on page 197.

Configuration alternatives: Another alternative for configuring a grid is to invoke the

WebSphere eXtreme Scale application programming interface (API). Then, the actual Java

or Java EE application contains the configuration, and any modification of the configuration

requires you to repackage and redeploy the application. Note, however, that there might be

cases where using the API to configure a grid is desirable, for example when defining a

temporary grid, or if you want to hide the configuration from users, using the WebSphere

eXtreme Scale API can be a better approach.

We do not provide details about how to use the API to configure a grid. You can obtain

more information about how to use the API to configure a grid at this website:

http://publib.boulder.ibm.com/infocenter/wxsinfo/v7r1/topic/com.ibm.websphere.e

xtremescale.prog.doc/cxsprgrm.html

Chapter 5. Grid configuration 73

– MapEventListener plug-in

– numberOfBuckets attribute (which can be used to turn off the near cache)

– ttlEvictorType attribute

– timeToLive attribute

You also can (and might have to) turn off the reference to a loader plug-in from your server

configuration.

We describe plug-ins later in this chapter, but for now, know that the client configuration can

specify these overrides. You can obtain information about the client ObjectGrid descriptor

XML file at this website:

http://publib.boulder.ibm.com/infocenter/wxsinfo/v7r1/index.jsp?topic=/com.ibm.web

sphere.extremescale.admin.doc/cxscliconfig.html

Typically, a client ObjectGrid descriptor XML file is packaged with the client Java EE

application. The application needs to explicitly use this file when connecting to the object grid,

as shown in Example 5-1.

Example 5-1 How to code connection to a grid with a client ObjectGrid descriptor XML file

URL objectgridxml = Thread.currentThread().getContextClassLoader()

.getResource("/META-INF/objectGridClient.xml");

String catalogEndpoint = ServerFactory.getServerProperties()

.getCatalogServiceBootstrap();

ClientClusterContext ccc = ObjectGridManagerFactory

.getObjectGridManager().connect(catalogEndpoint, null, objectgridxml);

ObjectGrid grid = ObjectGridManagerFactory.getObjectGridManager()

.getObjectGrid(ccc, "MyGrid");

Disabling near cache

A WebSphere eXtreme Scale client can maintain its own near-side cache, which is

automatically enabled when using lockStrategy="OPTIMISTIC" or "NONE". However, you can

disable this client cache using the client ObjectGrid descriptor XML file. You must set the

numberOfBuckets attribute of the BackingMap to zero (0), as shown in Example 5-2.

Example 5-2 Using a client ObjectGrid descriptor XML file to disable the near cache

<?xml version="1.0" encoding="UTF-8"?>

<objectGridConfig xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

xsi:schemaLocation="http://ibm.com/ws/objectgrid/config ../objectGrid.xsd"

xmlns="http://ibm.com/ws/objectgrid/config">

<objectGrids>

<objectGrid name="Grid">

<backingMap name="Test" numberOfBuckets="0" />

</objectGrid>

</objectGrids>

</objectGridConfig>