Currently, the default value of ClusterOptions.CLUSTER_IO_EXECUTOR_POOL_SIZE is #cores. I propose to increase it to 4 * #cores to support a higher load of blocking IO operations.
Moreover, I propose to use a cached thread pool instead of a fixed thread pool. That way, only those use cases which have high IO load will actually occupy the required resources to start more threads.
Last but not least, I propose to change the config option name from cluster.io-executor.pool-size to cluster.io-pool.size which is a bit shorter.