Best Practices for Coherence Portable Object Format (POF)

POF objects are indexed so it is possible to quickly traverse/navigate the binary (serialized form) to a specific element for extraction or updating using the indices without de-serializing the entire binary. Out of the box, coherence provides SimplePofPath class that can navigate a POF value based on integer indices. In the simplest form, all you need to do is to provide the index of the attribute that you want to extract/update. Some of the best practices that are coming to my mind are as under:

• Order your reads and writes: start with the lowest index value in the serialization routine and finish with the highest. When deserializing a value, perform reads in the same order as writes.
• Use the smallest possible integer for indexing the objects
• Non-contiguous indexes are acceptable but must be read/written sequentially.
• For subclasses reserve index ranges: index's are cumulative across derived types. As such, each derived type must be aware of the POF index range reserved by its super class.
• Do not re-purpose indexes: to support Evolvable, it's imperative that indexes of attributes are not re-purposed across class revisions.
• Label each of the index for the attribute
• The most frequently used attribute in the Filter(s) and Extractor(s) should be assigned lowest index.
• Enable POF Object  reference if the objects have circular/nested references (feature available in 3.7.1 + only)

Coherence: POF Exceptions

If you are trying to use POF for object serialization as recommended for better performance and less RAM utilization with Coherence, there are 2 ways to implement it:

1. Implement PortableObject interface for all objects that will be stored in the Coherence Grid - Need to modify the object class and implement readExternal and writeExternal methods.
2. Externalize the serialization logic by creating classes that implement PofSerializer interface and logic for serialization and de-serialization of your objects is implemented in this class using the serialize/deserialize methods. Later, you can map this class as the serializer for your object in pof-config.xml

More details on both the above ways can be found here.

If you are getting an error while using the PortableObject interface as below:

Caused by: java.io.EOFException: user type POF stream terminated at com.tangosol.io.pof.PofBufferWriter$UserTypeWriter.writeUserTypeInfo(PofBufferWriter.java:2621) at com.tangosol.io.pof.PofBufferWriter$UserTypeWriter.writeRemainder(PofBufferWriter.java:2497) at com.tangosol.io.pof.PortableObjectSerializer.serialize(PortableObjectSerializer.java:96) at com.tangosol.io.pof.PofBufferWriter.writeUserType(PofBufferWriter.java:1667)
... 13 more

Remember to remove the readRemainder() and writeRemainder() from the readExternal/writeExternal methods as they are used with POFSerializer interface.