Red Hat Summit10.5.4.4. Topology Change Headers for Hash Distribution-Aware Clients
The response header sent to clients when a topology change is returned by the server includes the following elements:
| Field | Data Type/Size | Details |
|---|---|---|
| Response Header with Topology Change Marker | - | - |
| Topology ID | vInt | - |
| Number Key Owners | Unsigned short. 2 bytes. | Contains the number of globally configured copies for each distributed key. Contains the value 0 if distribution is not configured on the cache. |
| Hash Function Version | 1 byte | Contains a pointer to the hash function in use. Contains the value 0 if distribution is not configured on the cache. |
| Hash Space Size | vInt | Contains the modulus used by JBoss Data Grid for all module arithmetic related to hash code generation. Clients use this information to apply the correct hash calculations to the keys. Contains the value 0 if distribution is not configured on the cache. |
| Number servers in topology | vInt | Contains the number of Hot Rod servers running in the cluster. This value can be a subset of the entire cluster if only some nodes are running Hot Rod servers. This value also represents the number of host to port pairings included in the header. |
| Number Virtual Nodes Owners | vInt | Contains the number of configured virtual nodes. Contains the value 0 if no virtual nodes are configured or if distribution is not configured on the cache. |
| mX: Host/IP Length | vInt | Contains the length of the hostname or IP address of an individual cluster member. Variable length allows this element to include hostnames, IPv4 and IPv6 addresses. |
| mX: Host/IP Address | string | Contains the hostname or IP address of an individual cluster member. The Hot Rod client uses this information to access the individual cluster member. |
| mX: Port | Unsigned short. 2 bytes. | Contains the port used by Hot Rod clients to communicate with the cluster member. |
| mX: Hashcode | 4 bytes. |
The three entries with the prefix
mX, are repeated for each server in the topology. The first server in the topology's information fields will be prefixed with m1 and the numerical value is incremented by one for each additional server till the value of X equals the number of servers specified in the num servers in topology field.
