private static Node requireNode(NodeMutex nodeMutex) {
        Node node = nodeMutex.node();
        if (node.state() != Node.State.active) throw new IllegalArgumentException("Node " + node + " must be " + Node.State.active + ", but is " + node.status());
        if (node.type() != NodeType.tenant) throw new IllegalArgumentException("Node " + node + " has unexpected type " + node.type());
        Optional<ClusterSpec> clusterSpec = node.allocation().map(Allocation::membership).map(ClusterMembership::cluster);
        if (clusterSpec.isEmpty() || clusterSpec.get().type() != ClusterSpec.Type.content) {
            throw new IllegalArgumentException("Node " + node + " is not a member of a content cluster: Refusing to write snapshot");
        }
        return node;
    }
Returns the key pair to use when sealing the snapshot encryption key
node-repository/src/main/java/com/yahoo/vespa/hosted/provision/backup/Snapshots.java