private Optional<FileRegistry> getFileRegistry(Version vespaVersion) {
        // Assumes at least one file registry, which we always have.
        Optional<FileRegistry> fileRegistry = Optional.ofNullable(fileRegistryMap.get(vespaVersion));
        if (fileRegistry.isEmpty()) {
            fileRegistry = Optional.of(fileRegistryMap.values().iterator().next());
        }
        return fileRegistry;
    }
Reads allocated hosts at the given node.

@return the allocated hosts at this node or empty if there is no data at this path
configserver/src/main/java/com/yahoo/vespa/config/server/zookeeper/ZKApplicationPackage.java