final boolean canUpgradeTo(Version version, Instant instant, Node node) {
        if (deferringUpgrade(node, instant)) return false;
        Set<Version> versions = nodeRepository.osVersions().availableTo(node, version);
        boolean versionAvailable = versions.contains(version);
        if (!versionAvailable) {
            LOG.log(Level.WARNING, "Want to upgrade host " + node.hostname() + " to OS version " +
                                   version.toFullString() + ", but this version does not exist in " +
                                   node.cloudAccount() + ". Found " + versions.stream().sorted().toList());
        }
        return versionAvailable;
    }
Returns whether node can upgrade to version at given instant
node-repository/src/main/java/com/yahoo/vespa/hosted/provision/os/OsUpgrader.java