public boolean isStandbyHostUsed(String standbyHost) {
      return this.selectedStandbyContainers.values().contains(standbyHost)
          || this.resourceRequests.stream().filter(request -> request.getPreferredHost().equals(standbyHost)).count() > 0;
    }
Encapsulates metadata concerning the failover of an active container.
samza-core/src/main/java/org/apache/samza/clustermanager/StandbyContainerManager.java