public int numberOfReasons() {
            int n = 0;
            if (insufficientVcpu) n++;
            if (insufficientMemoryGb) n++;
            if (insufficientDiskGb) n++;
            if (incompatibleDiskSpeed) n++;
            if (incompatibleArchitecture) n++;
            if (insufficientAvailableIPs) n++;
            if (violatesParentHostPolicy) n++;
            return n;
        }
Keeps track of the reason why a host rejected an allocation.
node-repository/src/main/java/com/yahoo/vespa/hosted/provision/maintenance/CapacityChecker.java