WAS v8.5 > New features > New features overview: Developing > WebSphere programming extensions

Introduction: Dynamic cache

Explore the key concepts pertaining to the dynamic cache service, which improves performance by caching the output of servlets, commands, web services, and JSP files.

The dynamic cache engine is the default cache provider for the dynamic cache APIs and framework. However, starting with v6.1.0.27, dynamic cache allows WebSphere eXtreme Scale, which is the is the strategic direction for caching for the WebSphere products, to act as its core caching engine.

Configuring the dynamic cache to use WebSphere eXtreme Scale lets you leverage transactional support, improved scalability, high availability, and other WebSphere eXtreme Scale features without changing your existing dynamic cache caching code. If you are currently using the default cache provider, we can use the dmgr console or wsadmin commands to replace the default dynamic cache provider with the WebSphere eXtreme Scale dynamic cache provider. We do not have to make any changes to your dynamic cache programming model. See the topic WebSphere eXtreme Scale dynamic cache provider in the WebSphere eXtreme Scale v7.0 Information Center for an overview of the WebSphere eXtreme Scale dynamic cache provider.

WebSphere eXtreme Scale can operate as an in-memory database processing space. We can use this processing space to provide in-line caching for a database back-end, or as a side cache. in-line caching uses WebSphere eXtreme Scale as the primary means for interacting with the data. When WebSphere eXtreme Scale is used as a side cache, the back-end is used in conjunction with WebSphere eXtreme Scale.

Functional advantages of using the WebSphere eXtreme Scale dynamic cache provider

The WebSphere eXtreme Scale dynamic cache provider:

• Supports memory-to-memory replication for sessions.
• Can handle all of the generic data and session caching needs of the applications.

• Enables the applications to leverage system memory without using SAN or storage solutions to host a dynamic cache disk cache.
• Provides a scalable replicated cache with a configurable number of replicas, thereby eliminating the need to use the data replication service (DRS), which the default cache provider uses. Use of DRS sometimes causes performance problems.
• Can be configured with additional WebSphere eXtreme Scale containers at runtime, thereby increasing your cache capacity, and preventing performance issues that sometimes occur when we use DRS. WebSphere eXtreme Scale automatically redistributes the partitions as new containers are added to the grid.
• Provides better caching qualities of service and control, than the default cache provider.

• Uses the same runtime monitoring and administration tools as the classic dynamic cache. These tools, such as the cache monitor and the dynamic cache runtime MBean, work the same way when dynamic cache runs on top of WebSphere eXtreme Scale, as when they are used with classic dynamic cache.

Functional differences between the default cache provider and the WebSphere eXtreme Scale dynamic cache provider

Following is a list of functional differences between the default cache provider and the WebSphere eXtreme Scale dynamic cache provider:

• WebSphere eXtreme Scale dynamic cache provider does not include disk cache support because all cache data is kept in memory. Therefore, the disk caching custom properties are not supported.
• WebSphere eXtreme Scale dynamic cache provider does not support the following features:
  • DistributedNioMap - skipMemoryAndWriteToDisk
  • DistributedMap and DistributedNioMap alias
  • Disabling dependency IDs or templates

• WebSphere eXtreme Scale dynamic cache provider does not support DRS style replication. Therefore, the DRS custom properties are not supported.

  When we use the WebSphere eXtreme Scale dynamic cache provider, replication configuration is controlled by the WebSphere eXtreme Scale deployment and definition files. See the topic Configure the dynamic cache provider for WebSphere eXtreme Scale in the WebSphere eXtreme Scale v7 Information Center for more information about replication.

• DistributedNioMapObject.release() is not called to release the byteBuffers for NIO buffer Management.
• WebSphere eXtreme Scale dynamic cache provider has limited PMI support. Certain PMI and MBean counters are no longer valid. See the topic Configure the dynamic cache provider for WebSphere eXtreme Scale in the WebSphere eXtreme Scale v7 Information Center for more information.

• When firing any event, ObjectGrid always sets the sourceOfInvalidation to REMOTE
• We can use the DynaCache API to register event listeners regardless of which cache provider you are using. However, if we use WebSphere eXtreme Scale dynamic cache provider, the event listeners work as expected for local in-memory caches. When co-located containers are being used, events are thrown on the machine where the request that caused the event is serviced instead of on the machine where the request originated. For example if an invalidate request is issued on Server A and the cache entry that gets invalidated is actually stored on Server B, then the event will be fired on Server B. With the default dynamic cache provider, the event is fired on Server A. When stand-alone containers are being used, no events are fired through the DynaCache event listener API.

Key concepts pertaining to the dynamic cache service

Explore the key concepts pertaining to the dynamic cache service, which improves performance by caching the output of servlets, commands, web services, and JSP files.

Cache instances

An application uses a cache instance to store, retrieve, and share data objects within the dynamic cache.

Use the dynamic cache service to improve performance

Caching the output of servlets, commands, and JSP (JSP) improves application performance. WebSphere Application Server consolidates several caching activities including servlets, web services, and WebSphere commands into one service called the dynamic cache. These caching activities work together to improve application performance, and share many configuration parameters that are set in the dynamic cache service of an application server.

Configure dynamic cache to use the WebSphere eXtreme Scale dynamic cache provider

Configure the dynamic cache service to use WebSphere eXtreme Scale lets you leverage transactional support, improved scalability, high availability, and other WebSphere eXtreme Scale features without changing your existing dynamic cache caching code.

Configure servlet caching

After a servlet is invoked and completes generating the output to cache, a cache entry is created containing the output and the side effects of the servlet. These side effects can include calls to other servlets or JSP files or metadata about the entry, including timeout and entry priority information.

Configure portlet fragment caching

After a portlet is invoked and completes generating the output to cache, a cache entry is created containing the output and the side effects of the portlet. These side effects can include calls to other portlets or metadata about the entry, including timeout and entry priority information.

Eviction policies using the disk cache garbage collector

The disk cache garbage collector is responsible for evicting objects out of the disk cache, based on a specified eviction policy.

Configure the JAX-RPC web services client cache

The web services client cache is a part of the dynamic cache service used to increase the performance of web services clients by caching responses from remote web services.

Cache monitor

Cache monitor is an installable web application that provides a real-time view of the current state of dynamic cache. You use it to help verify that dynamic cache is operating as expected. The only way to manipulate the data in the cache is using the cache monitor. It provides a GUI interface to manually change data.

Invalidation listeners

Invalidation listener mechanism uses Java events for alerting applications when contents are removed from the cache.

Related concepts:

Eviction policies using the disk cache garbage collector
Cache instances
Cache monitor
Invalidation listeners

Related

Tasks: Using the dynamic cache service to improve performance
Configure servlet caching
Configure portlet fragment caching
Configure the JAX-RPC web services client cache
Configure dynamic cache (DynaCache) to use the WebSphere eXtreme Scale dynamic cache provider

+

Search Tips   |   Advanced Search