About Terracotta Documentation
This documentation is about Terracotta DSO, an advanced distributed-computing technology aimed at meeting special clustering requirements.
Terracotta products without the overhead and complexity of DSO meet the needs of almost all use cases and clustering requirements. To learn how to migrate from Terracotta DSO to standard Terracotta products, see Migrating From Terracotta DSO. To find documentation on non-DSO (standard) Terracotta products, see Terracotta Documentation. Terracotta release information, such as release notes and platform compatibility, is found in Product Information.
- How DSO Clustering Works
- Platform Concepts
- Hello Clustered World
- Setup and Configuration
- Planning for a Clustered App
- Configuring Terracotta DSO
- Configuration Reference
- Using Annotations
- Cluster Events
- Data Locality Methods
- Distributed Cache
- Clustered Async Data Processing
- Tool Guides
- Developer Console
- Operations Center
- tim-get (TIM Management Tool)
- Platform Statistics Recorder
- Eclipse Plugin
- Sessions Configurator
- Clustering Spring Webapp with Sessions Configurator
- Testing, Tuning, and Deployment
- Top 5 Tuning Tips
- Testing a Clustered App
- Tuning a Clustered App
- Deployment Guide
- Operations Guide
- FAQs and Troubleshooting
- General FAQ
- DSO Technical FAQ
- Troubleshooting Guide
- Non-portable Classes
- Migrating From DSO
- Concept and Architecture Guide
- Examinator Reference Application
- Clustered Data Structures Guide
- Integrating Terracotta DSO
- Clustering Spring Framework
- Integration Modules Manual
- AspectWerkz Pattern Language
Publish Date: November, 2011
DSO Locality API
Working with clustered data can present additional challenges to applications which must manage this data across a series of application servers. Using the data locality methods available through the Terracotta Distributed Shared Objects (DSO) API's DsoCluster interface, you can meet these challenges by adding locality awareness to your application code. Adding locality awareness, or visibility, provides a number of advantages, including:
- Making applications more efficient with respect to data location by allowing code to be optimized along locality of reference.
- Exposing data access and usage patterns from within an application.
- Facilitating data commitment and eviction operations by providing information on the real-time location of clustered data or its absence.
- Allowing a cache to send work to the appropriate node by providing the location of data that requires processing.
- Providing insight into the effectiveness of data partitioning techniques by verifying the distribution of clustered data.
For more information on data structures, see the Terracotta DSO Data Structures Guide.
Classes that are injected with cluster awareness can call data locality methods.
The following code example shows the cluster-aware class
ClusterAwareClass with a member,
localityAwareFoo(), that calls the data locality method
See Terracotta DSO Cluster Events for more information on injecting cluster awareness into application classes.
The data-locality methods available are:
Note the following characteristics for these methods:
- None returns
null, making null checks unnecessary. In cases where there is no data to return, an empty Set or Map of empty Sets is returned (depending on the method's return type).
- An UnclusteredObjectException is thrown if any of the objects or a Map passed to one of these methods is not clustered.
- The "nodes" targeted by these methods refer to Terracotta nodes (application nodes with Terracotta running). Terracotta server instances are not subject data-locality checks.
- The values in the Sets or Maps of Sets returned by these methods are DsoNode instances. Each DsoNode instance is uniquely associated with a node and can identify that node by node ID, IP address, and hostname.
getNodesWithObject(Object object) to find which nodes contain the specified object in memory. This method has the following format:
getNodesWithObject(myObject) returns a Set containing the nodes which have myObject in memory. If myObject is not resident in any node's memory, an empty Set is returned. If myObject is not clustered, an UnclusteredObjectException is thrown.
getNodesWithObjects(Object objects ... )
getNodesWithObjects(Object objects ... ) to find which nodes contain the specified objects in memory. This method has the following format:
getNodesWithObject(myObject1, myObject2, myObject3) returns a Map with each key being one of the specified objects (myObject1, myObject2, or myObject3) and each value being a Set of nodes which have that object in memory. If an object is not resident in any node's memory, its corresponding value is an empty Set. If any of the objects specified is not clustered, an UnclusteredObjectException is thrown.
getNodesWithObjects(Collection objects) to find which nodes contain the objects from the specified Collection in memory. This method has the following format:
getNodesWithObjects(myObjects) returns a Map with each key being an object from the Collection myObjects and each value being a Set of nodes which have that object in memory. If an object is not resident in any node's memory, its corresponding value is an empty Set. If any of the objects in myObjects is not clustered, an UnclusteredObjectException is thrown.
getKeysForOrphanedValues(Map map) to generate a Set of keys for Map values (objects) that are not resident in the memory of any nodes. The map passed to
getKeysForOrphanedValues(Map map) must be clustered and support partial loading. This method has the following format:
getKeysForOrphanedValues(myMap) returns a Set of keys from myMap for any objects not found in memory on any node. If myMap is not clustered, an UnclusteredObjectException is thrown.
getKeysForLocalValues(Map map) to generate a Set of keys for Map values (objects) that are resident in the memory of the local node. The map passed to
getKeysForLocalValues(Map map) must be clustered and support partial loading. This method has the following format:
getKeysForLocalValues(myMap) returns a Set of keys from myMap for any objects found in the memory of the local node. If no objects from myMap are found, an empty Set is returned. If myMap is not clustered, an UnclusteredObjectException is thrown.