Chapter 8. Hot Rod Server

8.1. About Hot Rod

Hot Rod is a binary TCP client-server protocol used in Red Hat JBoss Data Grid. It was created to overcome deficiencies in other client/server protocols, such as Memcached.

Hot Rod will failover on a server cluster that undergoes a topology change. Hot Rod achieves this by providing regular updates to clients about the cluster topology.

Hot Rod enables clients to do smart routing of requests in partitioned or distributed Red Hat JBoss Data Grid server clusters. To do this, Hot Rod allows clients to determine the partition that houses a key and then communicate directly with the server that has the key. This functionality relies on Hot Rod updating the cluster topology with clients, and that the clients use the same consistent hash algorithm as the servers.

Red Hat JBoss Data Grid contains a server module that implements the Hot Rod protocol. The Hot Rod protocol facilitates faster client and server interactions in comparison to other text-based protocols and allows clients to make decisions about load balancing, failover and data location operations.

8.2. Worker Threads in the Hot Rod Server

8.2.1. About Worker Threads

Worker threads, unlike system threads, are threads activated by a client’s request and do not interact with the user. As the server is asynchronous client requests will continue to be received after this limit is hit; instead, this number represents the number of active threads performing simultaneous operations, typically writes.

In Red Hat JBoss Data Grid, worker threads are used as part of the configurations for the REST, Memcached and Hot Rod interfaces.

8.2.2. Change Number of Worker Threads

In Red Hat JBoss Data Grid, the default number of worker threads for all connectors is 160, and may be changed . The number of worker threads may be specified as an attribute on each interface, as seen in the following example: 

<hotrod-connector socket-binding="hotrod" cache-container="local" worker-threads="200">
    <!-- Additional configuration here -->
</hotrod-connector>