@Override
    public Function<ApplicationInstanceReference, HostInfos> getHostInfosByApplicationResolver() {
        hostInfosCache.refreshCache();
        return hostInfosCache::getCachedHostInfos;
    }
Cache is checked for freshness when this mapping is created, and may be invalidated again later
by other users of the cache. Since this function is backed by the cache, any such invalidation
will be reflected in the returned mapping; all users of the cache collaborate in repopulating it.
orchestrator/src/main/java/com/yahoo/vespa/orchestrator/status/ZkStatusService.java