The CacheResource utilizes BlockingPublisher to handle subscribing on a blocking thread.
https://github.com/infinispan/infinispan/blob/830bf17fa576575147337591b8417403b0e52805/server/core/src/main/java/org/infinispan/server/core/backup/resources/CacheResource.java#L243
Unfortunately, the Publisher it subscribes uses a flatMap operation which can return on a different thread. This means that thread would be the one that requests from the downstream "blocking" publisher that reads the disk. We need to move the blockingPublisher call further down to surround the Flowable.using Publisher.