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11.3. Hot Rod Hash Functions
Red Hat JBoss Data Grid uses a consistent hash function to place nodes and, subsequently, their corresponding keys on a hash wheel to determine where entries live.
The hash space value is constant and limited to the maximum 32-bit positive integer value (
Integer.MAX_INT). This value is returned to the client using the Hot Rod protocol each time a hash-topology change is detected to prevent Hot Rod clients assuming a specific hash space as a default. The hash space can only contain positive numbers ranging from 0 to Integer.MAX_INT.
When the Hot Rod protocol is used to interact with JBoss Data Grid, the keys (and their values) must be byte arrays to ensure platform neutral behavior. Smart clients (which are aware of hash distribution in the background) must be able to recalculate hash codes of such byte array keys in this platform-neutral manner. To accommodate this, version information for hash functions used in JBoss Data Grid is saved for implementation by non-Java clients, if required.
Client Intelligence Levels
The following table describes the client intelligence levels:
| Intelligence Level | Description |
|---|---|
| Level 1 | In this level, simple clients connect to the grid using a list of statically provided server addresses. These addresses are used based on round-robin scheduling. |
| Level 2 | In this level, clients are aware of the topology of the grid and are notified when new servers are added or removed from the grid. |
| Level 3 | In this level, clients use the grid topology and the key hashes to directly connect to the node that is the primary owner for a data item. Thus reducing the need for remote calls between the server nodes. |
