protected SamzaResource peekAllocatedResource(String host) {
    return resourceRequestState.peekResource(host);
  }
Retrieves, but does not remove, the first allocated resource on the specified host.

@param host  the host on which a resource is needed.
@return      the first {@link SamzaResource} allocated for the specified host or {@code null} if there isn't one.
samza-core/src/main/java/org/apache/samza/clustermanager/ContainerAllocator.java