Adding a new Datatype

DVID Datatypes allow customization of both the REST API and the way data is stored persistently. All current datatypes store data via key-value pairs. The developer chooses appropriate type-specific keys (storage.TKey), e.g., the labelblk datatype uses an encoded ZYX block coordinate as a type-specific key where its value is the serialized (compressed) slice of bytes representing the 64-bit labels for the 32 x 32 x 32 voxel block.

Please see the keyvalue datatype as a simple example of how to build a datatype. You create new datatype implementations by adding a Go package for the new datatype under the datatype directory. The keyvalue datatype is implemented with just three small files:

• keyvalue.go is the main file and includes the ServeHTTP() function that accepts the datatype-specific HTTP API requests, does computation, and returns the result.
• key.go shows how keys encode a (X,Y,Z) block coordinate into a TKey.
• keyvalue_test.go provides unit tests for the keyvalue datatype.

Note that when designing a TKey, the possible type-specific keys must be the same length or have a unique terminator that prevents one TKey being a prefix of another TKey.