public void resumeUpgradeOf(NodeType nodeType, boolean resume) {
        require(nodeType);
        try (Lock lock = db.lockOsVersionChange()) {
            OsVersionTarget target = readChange().targets().get(nodeType);
            if (target == null) return; // No target set for this type
            OsUpgrader upgrader = chooseUpgrader(nodeType, Optional.of(target.version()));
            if (resume) {
                upgrader.upgradeTo(target);
            } else {
                upgrader.disableUpgrade(nodeType);
            }
        }
    }
Resume or halt upgrade of given node type
node-repository/src/main/java/com/yahoo/vespa/hosted/provision/os/OsVersions.java