private Result checkRedundancySeenFromDistributor(DistributorNodeInfo distributorNodeInfo, Set<Integer> indexesToCheck) {
        Map<Integer, Integer> replication = new LinkedHashMap<>(minReplication(distributorNodeInfo));

        Integer minReplication = null;
        Integer minReplicationIndex = null;
        for (var entry : replication.entrySet()) {
            Integer value = entry.getValue();
            Integer nodeIndex = entry.getKey();
            if ( ! indexesToCheck.contains(nodeIndex)) continue;
            if (minReplication == null || (value != null && value < minReplication)) {
                minReplication = value;
                if (minReplication == null) continue;

                minReplicationIndex = nodeIndex;
                if (minReplication < requiredRedundancy) break;
            }
        }

        return verifyRedundancy(distributorNodeInfo, minReplication, minReplicationIndex);
    }
Verifies that storage nodes and distributors are up (or retired).
clustercontroller-core/src/main/java/com/yahoo/vespa/clustercontroller/core/NodeStateChangeChecker.java