Developing Applications

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Guidelines for Data Structures:

• Java objects that will be replicated should extend either the ConitRoot or ConitObject class.
• References into conits can only be made through an object that is a subclass of ConitRoot.
• ConitRoot subclasses must implement "nullifyReferences" until we have a bytecode transformer to handle adding the method. This requires making all references null and is called when evicting a conit from the cache.
• Any method that modifies the object must call "setDirty", which is defined and handled in the ConitRoot class.
• Classes that extend ConitRoot should implement a subclass of the Consistent interface that lists the methods that modify the object. In other words, methods that require committing or versioning should be prototyped in an interface that extends the Consistent interface.

• Using arrays and Java-defined collection classes is not fully tested and debugged.

Using the API

• Touch: Get updates for this object and its conit if the object could be stale.
• Fault: When an application on a secondary node follows a cross-conit reference to a conit that is not resident on that node, the node faults and fetches that conit from the primary node, which is usually the originating node.
• Commit: Push a conit's updates to the primary. If there is a conflict with the primary, the conit is evicted. When the conit is next accessed, the full conit is fetched from the primary.
• Evict: A conit can be thrown out of a cache. Only information about conit roots is saved because other conits may only refer into a conit through these objects.

Transforming Classes

After the data structures are compiled, they should be transformed to use the Ivory infrastructure through the API. This transformation can be done by hand or using the transformation classes that are in the xform directory. The xform directory contains the script we used to transform the test applications. We plan to have a toolkit to simplify transformation in the near future. The test applications use a combination of by-hand and automatic transformation.

• All data structure classes should be transformed using the AutoWriter class. This makes sure that the objects can be serialized and replicated at other sites.

Guidelines for Applications:

• Synchronize properly. Ivory does not do more synchronization than is necessary to replicate and cache data so as not to increase locking overhead.