WebSphere eXtreme Scale Best Practices for Operation and Management

Chapter 5. Grid configuration 87

When all three catalog servers are running, they establish a catalog service cluster where

one catalog server is elected to act as the master catalog service. The remaining catalog

servers will act as standby servers. The message from the SystemOut.log, which is shown in

Example 5-9, indicates that this catalog server acts as the master.

Example 5-9 Log message to provide the status of the catalog server cluster

[10/21/10 14:25:37:343 CDT] 00000012 CatalogServer I CWOBJ8109I: Updated catalog

service cluster CatalogCluster[thinkCell01, 1 master: 1 standbys] from server

thinkCell01\thinkNode02\nodeagent with entry CatalogServerEntry...

5.3 ObjectGrid plug-ins

A ObjectGrid plug-in is a plug-in that affects the behavior of a grid.

There are multiple ObjectGrid plug-ins:

򐂰 TransactionCallback: Provides transaction life-cycle events

򐂰 ObjectGridEventListener: Provides ObjectGrid life-cycle events for the ObjectGrid, shards,

and transactions

򐂰 SubjectSource, ObjectGridAuthorization, and SubjectValidation: Custom authentication

and authorization mechanisms

򐂰 MapAuthorization (deprecated): Custom authorization mechanism

This section describes the TransactionCallback and ObjectGridEventListener plug-ins.

5.3.1 The TransactionCallback plug-in

Create, read, update, and delete operations in a map happen in the context of an ObjectGrid

transaction. When the ObjectGrid interface is used to inline cache a database, the grid is

usually configured to use a loader plug-in. The loader plug-in is responsible for fetching data

from a back-end database to put into a WebSphere eXtreme Scale map or for reflecting the

changes that occur in a map into the back-end database.

A TransactionCallback plug-in allows the WebSphere eXtreme Scale transactions to be

coordinated with the transactions of the back-end system in the case where your application

accepts WebSphere eXtreme Scale as the transaction coordinator (meaning that your

application code explicitly calls the Session.begin(), Session.getMap(), and Session.commit()

methods). A TransactionCallback plug-in manages the begin and commit transaction

life-cycle events. WebSphere eXtreme Scale does not support two-phase commit

transactions (XA), but it has been reported that a WebSphere eXtreme Scale transaction can

be used successfully in a global transaction if it is the last participant (which is supported in

Important: Because the deployment manager now also acts as a catalog server, it has

become a more important part of the runtime infrastructure. Prior to use with WebSphere

eXtreme Scale, stopping and starting the deployment manager did not impact the

availability of applications running in the cell. However, stopping and starting the

deployment manager

does have an impact when the deployment manager is running a

catalog service. Stopping the deployment manager reduces the number of running catalog

servers. When quorum is enabled, the catalog service loses quorum, and no master

catalog server is active.