path: root/src/rpc/layout.rs

use std::cmp::Ordering;
use std::collections::HashMap;
use std::collections::HashSet;

use hex::ToHex;
use itertools::Itertools;

use serde::{Deserialize, Serialize};

use garage_util::crdt::{AutoCrdt, Crdt, LwwMap};
use garage_util::data::*;

use crate::graph_algo::*;

use crate::ring::*;

use std::convert::TryInto;

//The Message type will be used to collect information on the algorithm.
type Message = Vec<String>;

/// The layout of the cluster, i.e. the list of roles
/// which are assigned to each cluster node
#[derive(Clone, Debug, Serialize, Deserialize)]
pub struct ClusterLayout {
	pub version: u64,

	pub replication_factor: usize,
    #[serde(default="default_one")]
    pub zone_redundancy: usize,
  
    //This attribute is only used to retain the previously computed partition size, 
    //to know to what extent does it change with the layout update.
    #[serde(default="default_zero")]
    pub partition_size: u32,

	pub roles: LwwMap<Uuid, NodeRoleV>,

	/// node_id_vec: a vector of node IDs with a role assigned
	/// in the system (this includes gateway nodes).
	/// The order here is different than the vec stored by `roles`, because:
	/// 1. non-gateway nodes are first so that they have lower numbers holding
    ///     in u8 (the number of non-gateway nodes is at most 256).
	/// 2. nodes that don't have a role are excluded (but they need to
	///    stay in the CRDT as tombstones)
	pub node_id_vec: Vec<Uuid>,
	/// the assignation of data partitions to node, the values
	/// are indices in node_id_vec
	#[serde(with = "serde_bytes")]
	pub ring_assignation_data: Vec<CompactNodeType>,

	/// Role changes which are staged for the next version of the layout
	pub staging: LwwMap<Uuid, NodeRoleV>,
	pub staging_hash: Hash,
}

fn default_one() -> usize{
    return 1;
}
fn default_zero() -> u32{
    return 0;
}

const NB_PARTITIONS : usize = 1usize << PARTITION_BITS;

#[derive(PartialEq, Eq, PartialOrd, Ord, Clone, Debug, Serialize, Deserialize)]
pub struct NodeRoleV(pub Option<NodeRole>);

impl AutoCrdt for NodeRoleV {
	const WARN_IF_DIFFERENT: bool = true;
}

/// The user-assigned roles of cluster nodes
#[derive(PartialEq, Eq, PartialOrd, Ord, Clone, Debug, Serialize, Deserialize)]
pub struct NodeRole {
	/// Datacenter at which this entry belong. This information might be used to perform a better
	/// geodistribution
	pub zone: String,
	/// The (relative) capacity of the node
	/// If this is set to None, the node does not participate in storing data for the system
	/// and is only active as an API gateway to other nodes
	pub capacity: Option<u32>,
	/// A set of tags to recognize the node
	pub tags: Vec<String>,
}

impl NodeRole {
	pub fn capacity_string(&self) -> String {
		match self.capacity {
			Some(c) => format!("{}", c),
			None => "gateway".to_string(),
		}
	}

    pub fn tags_string(&self) -> String {
        let mut tags = String::new();
        if self.tags.len() == 0 {
            return tags
        }
        tags.push_str(&self.tags[0].clone());
        for t in 1..self.tags.len(){
            tags.push_str(",");
            tags.push_str(&self.tags[t].clone());
        }
        return tags;
    }
}

impl ClusterLayout {
	pub fn new(replication_factor: usize, zone_redundancy: usize) -> Self {
		let empty_lwwmap = LwwMap::new();
		let empty_lwwmap_hash = blake2sum(&rmp_to_vec_all_named(&empty_lwwmap).unwrap()[..]);

		ClusterLayout {
			version: 0,
			replication_factor,
            zone_redundancy,
            partition_size: 0,
			roles: LwwMap::new(),
			node_id_vec: Vec::new(),
			ring_assignation_data: Vec::new(),
			staging: empty_lwwmap,
			staging_hash: empty_lwwmap_hash,
		}
	}

	pub fn merge(&mut self, other: &ClusterLayout) -> bool {
		match other.version.cmp(&self.version) {
			Ordering::Greater => {
				*self = other.clone();
				true
			}
			Ordering::Equal => {
				self.staging.merge(&other.staging);

				let new_staging_hash = blake2sum(&rmp_to_vec_all_named(&self.staging).unwrap()[..]);
				let changed = new_staging_hash != self.staging_hash;

				self.staging_hash = new_staging_hash;

				changed
			}
			Ordering::Less => false,
		}
	}

	/// Returns a list of IDs of nodes that currently have
	/// a role in the cluster
	pub fn node_ids(&self) -> &[Uuid] {
		&self.node_id_vec[..]
	}

	pub fn num_nodes(&self) -> usize {
		self.node_id_vec.len()
	}

	/// Returns the role of a node in the layout
	pub fn node_role(&self, node: &Uuid) -> Option<&NodeRole> {
		match self.roles.get(node) {
			Some(NodeRoleV(Some(v))) => Some(v),
			_ => None,
		}
	}

    ///Returns the uuids of the non_gateway nodes in self.node_id_vec.
    pub fn useful_nodes(&self) -> Vec<Uuid> {
        let mut result = Vec::<Uuid>::new();
        for uuid in self.node_id_vec.iter() {
            match self.node_role(uuid) {
                Some(role) if role.capacity != None => result.push(*uuid),
                _ => ()
            }
        }
        return result;
    }

    ///Given a node uuids, this function returns the label of its zone
    pub fn get_node_zone(&self, uuid : &Uuid) -> Result<String,String> {
        match self.node_role(uuid) {
            Some(role) => return Ok(role.zone.clone()),
            _ => return Err("The Uuid does not correspond to a node present in the cluster.".to_string())
        }
    }
    
    ///Given a node uuids, this function returns its capacity or fails if it does not have any
    pub fn get_node_capacity(&self, uuid : &Uuid) -> Result<u32,String> {
        match self.node_role(uuid) {
            Some(NodeRole{capacity : Some(cap), zone: _, tags: _}) => return Ok(*cap),
            _ => return Err("The Uuid does not correspond to a node present in the \
                    cluster or this node does not have a positive capacity.".to_string())
        }
    }

    ///Returns the sum of capacities of non gateway nodes in the cluster
    pub fn get_total_capacity(&self) -> Result<u32,String> {
        let mut total_capacity = 0;
        for uuid in self.useful_nodes().iter() {
            total_capacity += self.get_node_capacity(uuid)?;
        }
        return Ok(total_capacity);
    }


	/// Check a cluster layout for internal consistency
	/// returns true if consistent, false if error
	pub fn check(&self) -> bool {
		// Check that the hash of the staging data is correct
		let staging_hash = blake2sum(&rmp_to_vec_all_named(&self.staging).unwrap()[..]);
		if staging_hash != self.staging_hash {
			return false;
		}

		// Check that node_id_vec contains the correct list of nodes
		let mut expected_nodes = self
			.roles
			.items()
			.iter()
			.filter(|(_, _, v)| v.0.is_some())
			.map(|(id, _, _)| *id)
			.collect::<Vec<_>>();
		expected_nodes.sort();
		let mut node_id_vec = self.node_id_vec.clone();
		node_id_vec.sort();
		if expected_nodes != node_id_vec {
			return false;
		}

		// Check that the assignation data has the correct length
		if self.ring_assignation_data.len() != (1 << PARTITION_BITS) * self.replication_factor {
			return false;
		}

		// Check that the assigned nodes are correct identifiers
		// of nodes that are assigned a role
		// and that role is not the role of a gateway nodes
		for x in self.ring_assignation_data.iter() {
			if *x as usize >= self.node_id_vec.len() {
				return false;
			}
			let node = self.node_id_vec[*x as usize];
			match self.roles.get(&node) {
				Some(NodeRoleV(Some(x))) if x.capacity.is_some() => (),
				_ => return false,
			}
		}

        //Check that every partition is associated to distinct nodes
        let rf = self.replication_factor;
        for p in 0..(1 << PARTITION_BITS) {
            let nodes_of_p = self.ring_assignation_data[rf*p..rf*(p+1)].to_vec();
            if nodes_of_p.iter().unique().count() != rf {
                return false;
            }
            //Check that every partition is spread over at least zone_redundancy zones.
            let zones_of_p = nodes_of_p.iter()
                    .map(|n| self.get_node_zone(&self.node_id_vec[*n as usize])
                         .expect("Zone not found."));
            if zones_of_p.unique().count() < self.zone_redundancy {
                return false;
            }
        }

        //Check that the nodes capacities is consistent with the stored partitions
        let mut node_usage = vec![0; MAX_NODE_NUMBER];
        for n in self.ring_assignation_data.iter() {
            node_usage[*n as usize] += 1;
        }
        for n in 0..MAX_NODE_NUMBER {
            if node_usage[n] > 0 {
                let uuid = self.node_id_vec[n];
                if node_usage[n]*self.partition_size > self.get_node_capacity(&uuid)
                                .expect("Critical Error"){
                    return false;
                }
            }
        }

        //Check that the partition size stored is the one computed by the asignation
        //algorithm.
        let cl2 = self.clone();
        let (_ , zone_to_id) = cl2.generate_zone_ids().expect("Critical Error");
        let partition_size = cl2.compute_optimal_partition_size(&zone_to_id).expect("Critical Error");
        if partition_size != self.partition_size {
            return false;
        }


		true
	}

}

impl ClusterLayout {
	/// This function calculates a new partition-to-node assignation.
	/// The computed assignation respects the node replication factor
    /// and the zone redundancy parameter It maximizes the capacity of a
	/// partition (assuming all partitions have the same size).
	/// Among such optimal assignation, it minimizes the distance to
	/// the former assignation (if any) to minimize the amount of
	/// data to be moved. 
	pub fn calculate_partition_assignation(&mut self, replication:usize, redundancy:usize) -> Result<Message,String> {
		//The nodes might have been updated, some might have been deleted.
		//So we need to first update the list of nodes and retrieve the
		//assignation.
        
        //We update the node ids, since the node list might have changed with the staged
        //changes in the layout. We retrieve the old_assignation reframed with the new ids
        let old_assignation_opt = self.update_node_id_vec()?;
        self.replication_factor = replication;
        self.zone_redundancy = redundancy;
        
        let mut msg = Message::new();
        msg.push(format!("Computation of a new cluster layout where partitions are \
        replicated {} times on at least {} distinct zones.", replication, redundancy));

        //We generate for once numerical ids for the zone, to use them as indices in the 
        //flow graphs.
        let (id_to_zone , zone_to_id) = self.generate_zone_ids()?;

        msg.push(format!("The cluster contains {} nodes spread over {} zones.", 
                         self.useful_nodes().len(), id_to_zone.len()));
       
        //We compute the optimal partition size
        //Capacities should be given in a unit so that partition size is at least 100.
        //In this case, integer rounding plays a marginal role in the percentages of 
        //optimality.
        let partition_size = self.compute_optimal_partition_size(&zone_to_id)?;
        if old_assignation_opt != None  {
            msg.push(format!("Given the replication and redundancy constraint, the \
                optimal size of a partition is {}. In the previous layout, it used to \
                be {}.", partition_size, self.partition_size));
        }
        else {
            msg.push(format!("Given the replication and redundancy constraints, the \
                optimal size of a partition is {}.", partition_size));
        }
        self.partition_size = partition_size;

        //We compute a first flow/assignment that is heuristically close to the previous
        //assignment
        let mut gflow = self.compute_candidate_assignment( &zone_to_id, &old_assignation_opt)?;
        if let Some(assoc) = &old_assignation_opt {
            //We minimize the distance to the previous assignment.
            self.minimize_rebalance_load(&mut gflow, &zone_to_id, &assoc)?;
        }

        msg.append(&mut self.output_stat(&gflow, &old_assignation_opt, &zone_to_id,&id_to_zone)?);
        msg.push("".to_string());

        //We update the layout structure
        self.update_ring_from_flow(id_to_zone.len() , &gflow)?;
        return Ok(msg);
    }

	/// The LwwMap of node roles might have changed. This function updates the node_id_vec
	/// and returns the assignation given by ring, with the new indices of the nodes, and
	/// None if the node is not present anymore.
	/// We work with the assumption that only this function and calculate_new_assignation
	/// do modify assignation_ring and node_id_vec.
    fn update_node_id_vec(&mut self) -> Result< Option< Vec<Vec<usize> > > ,String> {
        // (1) We compute the new node list
        //Non gateway nodes should be coded on 8bits, hence they must be first in the list
	    //We build the new node ids	 
		let mut new_non_gateway_nodes: Vec<Uuid> = self.roles.items().iter()
            .filter(|(_, _, v)| 
                        match &v.0 {Some(r) if r.capacity != None => true, _=> false })
            .map(|(k, _, _)| *k).collect();
        
        if new_non_gateway_nodes.len() > MAX_NODE_NUMBER {
            return Err(format!("There are more than {} non-gateway nodes in the new \
                            layout. This is not allowed.", MAX_NODE_NUMBER).to_string());
        }

		let mut new_gateway_nodes: Vec<Uuid> = self.roles.items().iter()
            .filter(|(_, _, v)| 
                        match v {NodeRoleV(Some(r)) if r.capacity == None => true, _=> false })
            .map(|(k, _, _)| *k).collect();

        let nb_useful_nodes = new_non_gateway_nodes.len();
        let mut new_node_id_vec = Vec::<Uuid>::new();
        new_node_id_vec.append(&mut new_non_gateway_nodes);
        new_node_id_vec.append(&mut new_gateway_nodes);
        
        
        // (2) We retrieve the old association
        //We rewrite the old association with the new indices. We only consider partition
        //to node assignations where the node is still in use.
        let nb_partitions = 1usize << PARTITION_BITS;
        let mut old_assignation = vec![ Vec::<usize>::new() ; nb_partitions];
        
        if self.ring_assignation_data.len() == 0 {
            //This is a new association
            return Ok(None);
        }
        if self.ring_assignation_data.len() != nb_partitions * self.replication_factor {
            return Err("The old assignation does not have a size corresponding to \
                the old replication factor or the number of partitions.".to_string());
        }

        //We build a translation table between the uuid and new ids
        let mut uuid_to_new_id = HashMap::<Uuid, usize>::new();
        
        //We add the indices of only the new non-gateway nodes that can be used in the
        //association ring
        for i in 0..nb_useful_nodes {
            uuid_to_new_id.insert(new_node_id_vec[i], i );
        }

        let rf= self.replication_factor;
        for p in 0..nb_partitions {
            for old_id in &self.ring_assignation_data[p*rf..(p+1)*rf] {
                let uuid = self.node_id_vec[*old_id as usize];
                if uuid_to_new_id.contains_key(&uuid) {
                    old_assignation[p].push(uuid_to_new_id[&uuid]);
                }
            }
        }

        //We write the results
        self.node_id_vec = new_node_id_vec;
        self.ring_assignation_data = Vec::<CompactNodeType>::new();

        return Ok(Some(old_assignation));
	}


    ///This function generates ids for the zone of the nodes appearing in 
    ///self.node_id_vec.
    fn generate_zone_ids(&self) -> Result<(Vec<String>, HashMap<String, usize>),String>{
        let mut id_to_zone = Vec::<String>::new();
        let mut zone_to_id = HashMap::<String,usize>::new();

        for uuid in self.node_id_vec.iter() {
            if self.roles.get(uuid) == None {
                return Err("The uuid was not found in the node roles (this should \
                    not happen, it might be a critical error).".to_string());
            }
            match self.node_role(&uuid) {
                Some(r) => if !zone_to_id.contains_key(&r.zone) && r.capacity != None {
                            zone_to_id.insert(r.zone.clone() , id_to_zone.len());
                            id_to_zone.push(r.zone.clone());
                        }
                _ => ()
            }
        }
        return Ok((id_to_zone, zone_to_id));
    }

    ///This function computes by dichotomy the largest realizable partition size, given
    ///the layout.
    fn compute_optimal_partition_size(&self, zone_to_id: &HashMap<String, usize>) -> Result<u32,String>{
        let nb_partitions = 1usize << PARTITION_BITS;
        let empty_set = HashSet::<(usize,usize)>::new();
        let mut g = self.generate_flow_graph(1, zone_to_id, &empty_set)?;
        g.compute_maximal_flow()?;
        if g.get_flow_value()? < (nb_partitions*self.replication_factor).try_into().unwrap() {
            return Err("The storage capacity of he cluster is to small. It is \
                       impossible to store partitions of size 1.".to_string());
        }

        let mut s_down = 1;
        let mut s_up = self.get_total_capacity()?;
        while s_down +1 < s_up {
            g = self.generate_flow_graph((s_down+s_up)/2, zone_to_id, &empty_set)?;
            g.compute_maximal_flow()?;
            if g.get_flow_value()? < (nb_partitions*self.replication_factor).try_into().unwrap() {
                s_up = (s_down+s_up)/2;
            }
            else {
                s_down = (s_down+s_up)/2;
            }
        }

        return Ok(s_down);
    }
    
    fn generate_graph_vertices(nb_zones : usize, nb_nodes : usize) -> Vec<Vertex> {
        let mut vertices = vec![Vertex::Source, Vertex::Sink];
        for p in 0..NB_PARTITIONS {
            vertices.push(Vertex::Pup(p));
            vertices.push(Vertex::Pdown(p));
            for z in 0..nb_zones {
                vertices.push(Vertex::PZ(p, z));
            }
        }
        for n in 0..nb_nodes {
            vertices.push(Vertex::N(n));
        }
        return vertices;
    }

    fn generate_flow_graph(&self, size: u32, zone_to_id: &HashMap<String, usize>, exclude_assoc : &HashSet<(usize,usize)>) -> Result<Graph<FlowEdge>, String> {
        let vertices = ClusterLayout::generate_graph_vertices(zone_to_id.len(), 
                                                        self.useful_nodes().len());
        let mut g= Graph::<FlowEdge>::new(&vertices);
        let nb_zones = zone_to_id.len();
        for p in 0..NB_PARTITIONS {
            g.add_edge(Vertex::Source, Vertex::Pup(p), self.zone_redundancy as u32)?;
            g.add_edge(Vertex::Source, Vertex::Pdown(p), (self.replication_factor - self.zone_redundancy) as u32)?;
            for z in 0..nb_zones {
                g.add_edge(Vertex::Pup(p) , Vertex::PZ(p,z) , 1)?;
                g.add_edge(Vertex::Pdown(p) , Vertex::PZ(p,z) , 
                            self.replication_factor as u32)?;
            }
        }
        for n in 0..self.useful_nodes().len() {
            let node_capacity = self.get_node_capacity(&self.node_id_vec[n])?;
            let node_zone = zone_to_id[&self.get_node_zone(&self.node_id_vec[n])?]; 
            g.add_edge(Vertex::N(n), Vertex::Sink, node_capacity/size)?;
            for p in 0..NB_PARTITIONS {
                if !exclude_assoc.contains(&(p,n))  {
                    g.add_edge(Vertex::PZ(p, node_zone), Vertex::N(n), 1)?;
                }
            }
        }
        return Ok(g);
    }


    fn compute_candidate_assignment(&self, zone_to_id: &HashMap<String, usize>, 
        old_assoc_opt : &Option<Vec< Vec<usize> >>) -> Result<Graph<FlowEdge>, String > {
        
        //We list the edges that are not used in the old association
        let mut exclude_edge = HashSet::<(usize,usize)>::new();
        if let Some(old_assoc) = old_assoc_opt {
            let nb_nodes = self.useful_nodes().len();
            for p in 0..NB_PARTITIONS {
                for n in 0..nb_nodes {
                    exclude_edge.insert((p,n));
                }
                for n in old_assoc[p].iter() {
                    exclude_edge.remove(&(p,*n));
                }
            }
        }

        //We compute the best flow using only the edges used in the old assoc
        let mut g = self.generate_flow_graph(self.partition_size, zone_to_id, &exclude_edge )?;
        g.compute_maximal_flow()?;
        for (p,n) in exclude_edge.iter() {
            let node_zone = zone_to_id[&self.get_node_zone(&self.node_id_vec[*n])?]; 
            g.add_edge(Vertex::PZ(*p,node_zone), Vertex::N(*n), 1)?;
        }
        g.compute_maximal_flow()?;
        return Ok(g);
    }

    fn minimize_rebalance_load(&self, gflow: &mut Graph<FlowEdge>, zone_to_id: &HashMap<String, usize>, old_assoc : &Vec< Vec<usize> >) -> Result<(), String > {
        let mut cost = CostFunction::new();
        for p in 0..NB_PARTITIONS {
            for n in old_assoc[p].iter() {
                let node_zone = zone_to_id[&self.get_node_zone(&self.node_id_vec[*n])?]; 
                cost.insert((Vertex::PZ(p,node_zone), Vertex::N(*n)), -1);
            }
        }
        let nb_nodes = self.useful_nodes().len();
        let path_length = 4*nb_nodes;
        gflow.optimize_flow_with_cost(&cost, path_length)?;

        return Ok(());
    }

    fn update_ring_from_flow(&mut self, nb_zones : usize, gflow: &Graph<FlowEdge> ) -> Result<(), String>{
        self.ring_assignation_data = Vec::<CompactNodeType>::new();
        for p in 0..NB_PARTITIONS {
            for z in 0..nb_zones {
                let assoc_vertex = gflow.get_positive_flow_from(Vertex::PZ(p,z))?;
                for vertex in assoc_vertex.iter() {
                    match vertex{
                        Vertex::N(n) => self.ring_assignation_data.push((*n).try_into().unwrap()),
                        _ => ()
                    }
                }
            }
        }

        if self.ring_assignation_data.len() != NB_PARTITIONS*self.replication_factor {
            return Err("Critical Error : the association ring we produced does not \
                       have the right size.".to_string());
        }
        return Ok(());
    }
     

    //This function returns a message summing up the partition repartition of the new
    //layout.
    fn output_stat(&self , gflow : &Graph<FlowEdge>, 
                    old_assoc_opt : &Option< Vec<Vec<usize>> >,
                    zone_to_id: &HashMap<String, usize>, 
                    id_to_zone : &Vec<String>) -> Result<Message, String>{
        let mut msg = Message::new();
        
		let nb_partitions = 1usize << PARTITION_BITS;
        let used_cap = self.partition_size * nb_partitions as u32 * 
                self.replication_factor as u32;
        let total_cap = self.get_total_capacity()?;
        let percent_cap = 100.0*(used_cap as f32)/(total_cap as f32);
        msg.push(format!("Available capacity / Total cluster capacity: {} / {} ({:.1} %)",
            used_cap , total_cap , percent_cap ));
        msg.push(format!(""));
        msg.push(format!("If the percentage is to low, it might be that the \
        replication/redundancy constraints force the use of nodes/zones with small \
        storage capacities. \
        You might want to rebalance the storage capacities or relax the constraints. \
        See the detailed statistics below and look for saturated nodes/zones."));
        msg.push(format!("Recall that because of the replication, the actual available \
                         storage capacity is {} / {} = {}.", 
                        used_cap , self.replication_factor , 
                        used_cap/self.replication_factor as u32));
       
        //We define and fill in the following tables
        let storing_nodes = self.useful_nodes();
        let mut new_partitions = vec![0; storing_nodes.len()];
        let mut stored_partitions = vec![0; storing_nodes.len()];

        let mut new_partitions_zone = vec![0; id_to_zone.len()];
        let mut stored_partitions_zone = vec![0; id_to_zone.len()];

        for p in 0..nb_partitions {
            for z in 0..id_to_zone.len() {
                let pz_nodes = gflow.get_positive_flow_from(Vertex::PZ(p,z))?;
                if pz_nodes.len() > 0 {
                    stored_partitions_zone[z] += 1;
                    if let Some(old_assoc) = old_assoc_opt {
                        let mut old_zones_of_p = Vec::<usize>::new();
                        for n in old_assoc[p].iter() {
                            old_zones_of_p.push(
                                zone_to_id[&self.get_node_zone(&self.node_id_vec[*n])?]);
                        }
                        if !old_zones_of_p.contains(&z) {
                            new_partitions_zone[z] += 1;
                        }
                    }
                }
                for vert in pz_nodes.iter() {
                    if let Vertex::N(n) = *vert {
                        stored_partitions[n] += 1;
                        if let Some(old_assoc) = old_assoc_opt {
                            if !old_assoc[p].contains(&n) {
                                new_partitions[n] += 1;
                            }
                        }
                    }
                }
            }
        }

        if *old_assoc_opt == None {
            new_partitions = stored_partitions.clone();
            new_partitions_zone = stored_partitions_zone.clone();
        }
        
        //We display the statistics

        msg.push(format!(""));
        if *old_assoc_opt != None {
            let total_new_partitions : usize = new_partitions.iter().sum();
            msg.push(format!("A total of {} new copies of partitions need to be \
                             transferred.", total_new_partitions));
        }
        msg.push(format!(""));
        msg.push(format!("Detailed statistics by zones and nodes."));
        
        for z in 0..id_to_zone.len(){
            let mut nodes_of_z = Vec::<usize>::new();
            for n in 0..storing_nodes.len(){
                if self.get_node_zone(&self.node_id_vec[n])? == id_to_zone[z] {
                    nodes_of_z.push(n);
                }
            }
            let replicated_partitions : usize = nodes_of_z.iter()
                    .map(|n| stored_partitions[*n]).sum();
            msg.push(format!(""));
            
            msg.push(format!("Zone {}: {} distinct partitions stored ({} new, \
                {} partition copies) ", id_to_zone[z], stored_partitions_zone[z], 
                                 new_partitions_zone[z], replicated_partitions));
            
            let available_cap_z : u32 = self.partition_size*replicated_partitions as u32;
            let mut total_cap_z = 0;
            for n in nodes_of_z.iter() {
                total_cap_z += self.get_node_capacity(&self.node_id_vec[*n])?;
            }
            let percent_cap_z = 100.0*(available_cap_z as f32)/(total_cap_z as f32);
            msg.push(format!("  Available capacity / Total capacity: {}/{} ({:.1}%).",
                available_cap_z, total_cap_z, percent_cap_z));
            
            for n in nodes_of_z.iter() {
                let available_cap_n = stored_partitions[*n] as u32 *self.partition_size;
                let total_cap_n =self.get_node_capacity(&self.node_id_vec[*n])?;
                let tags_n = (self.node_role(&self.node_id_vec[*n])
                                .ok_or("Node not found."))?.tags_string();
                msg.push(format!("  Node {}: {} partitions ({} new) ; \
                                 available/total capacity: {} / {} ({:.1}%) ; tags:{}", 
                        &self.node_id_vec[*n].to_vec()[0..2].to_vec().encode_hex::<String>(), 
                        stored_partitions[*n], 
                        new_partitions[*n], available_cap_n, total_cap_n,
                        (available_cap_n as f32)/(total_cap_n as f32)*100.0 ,
                        tags_n));
            }
        }

        return Ok(msg);
    }
    
}

//====================================================================================

#[cfg(test)]
mod tests {
	use super::*;
    use std::io::*;
//	use itertools::Itertools;
/*
	fn check_assignation(cl: &ClusterLayout) {
		//Check that input data has the right format
		let nb_partitions = 1usize << PARTITION_BITS;
		assert!(cl.ring_assignation_data.len() == nb_partitions * cl.replication_factor);

		//Check that is is a correct assignation with zone redundancy
		let rf = cl.replication_factor;
		for i in 0..nb_partitions {
			assert!(
				rf == cl.ring_assignation_data[rf * i..rf * (i + 1)]
					.iter()
					.map(|nod| node_zone[*nod as usize].clone())
					.unique()
					.count()
			);
		}

		let nb_nodes = cl.node_id_vec.len();
		//Check optimality
		let node_nb_part = (0..nb_nodes)
			.map(|i| {
				cl.ring_assignation_data
					.iter()
					.filter(|x| **x == i as u8)
					.count()
			})
			.collect::<Vec<_>>();

		let zone_vec = node_zone.iter().unique().collect::<Vec<_>>();
		let zone_nb_part = zone_vec
			.iter()
			.map(|z| {
				cl.ring_assignation_data
					.iter()
					.filter(|x| node_zone[**x as usize] == **z)
					.count()
			})
			.collect::<Vec<_>>();

		//Check optimality of the zone assignation : would it be better for the
		//node_capacity/node_partitions ratio to change the assignation of a partition

		if let Some(idmin) = (0..nb_nodes).min_by(|i, j| {
			(node_capacity[*i] * node_nb_part[*j] as u32)
				.cmp(&(node_capacity[*j] * node_nb_part[*i] as u32))
		}) {
			if let Some(idnew) = (0..nb_nodes)
				.filter(|i| {
					if let Some(p) = zone_vec.iter().position(|z| **z == node_zone[*i]) {
						zone_nb_part[p] < nb_partitions
					} else {
						false
					}
				})
				.max_by(|i, j| {
					(node_capacity[*i] * (node_nb_part[*j] as u32 + 1))
						.cmp(&(node_capacity[*j] * (node_nb_part[*i] as u32 + 1)))
				}) {
				assert!(
					node_capacity[idmin] * (node_nb_part[idnew] as u32 + 1)
						>= node_capacity[idnew] * node_nb_part[idmin] as u32
				);
			}
		}

		//In every zone, check optimality of the nod assignation
		for z in zone_vec {
			let node_of_z_iter = (0..nb_nodes).filter(|id| node_zone[*id] == *z);
			if let Some(idmin) = node_of_z_iter.clone().min_by(|i, j| {
				(node_capacity[*i] * node_nb_part[*j] as u32)
					.cmp(&(node_capacity[*j] * node_nb_part[*i] as u32))
			}) {
				if let Some(idnew) = node_of_z_iter.min_by(|i, j| {
					(node_capacity[*i] * (node_nb_part[*j] as u32 + 1))
						.cmp(&(node_capacity[*j] * (node_nb_part[*i] as u32 + 1)))
				}) {
					assert!(
						node_capacity[idmin] * (node_nb_part[idnew] as u32 + 1)
							>= node_capacity[idnew] * node_nb_part[idmin] as u32
					);
				}
			}
		}
	}
*/
    
    fn show_msg(msg  : &Message) {
        for s in msg.iter(){
            println!("{}",s);
        }
    }

	fn update_layout(
		cl: &mut ClusterLayout,
		node_id_vec: &Vec<u8>,
		node_capacity_vec: &Vec<u32>,
		node_zone_vec: &Vec<String>,
	) {
		for i in 0..node_id_vec.len() {
			if let Some(x) = FixedBytes32::try_from(&[i as u8; 32]) {
				cl.node_id_vec.push(x);
			}

			let update = cl.roles.update_mutator(
				cl.node_id_vec[i],
				NodeRoleV(Some(NodeRole {
					zone: (node_zone_vec[i].to_string()),
					capacity: (Some(node_capacity_vec[i])),
					tags: (vec![]),
				})),
			);
			cl.roles.merge(&update);
		}
	}

	#[test]
	fn test_assignation() {
        std::io::stdout().flush().ok().expect("Could not flush stdout");
        let mut node_id_vec = vec![1, 2, 3];
		let mut node_capacity_vec = vec![4000, 1000, 2000];
		let mut node_zone_vec = vec!["A", "B", "C"]
			.into_iter()
			.map(|x| x.to_string())
			.collect();

		let mut cl = ClusterLayout {
			node_id_vec: vec![],

			roles: LwwMap::new(),

			replication_factor: 3,
            zone_redundancy: 1,
            partition_size: 0,
			ring_assignation_data: vec![],
			version: 0,
			staging: LwwMap::new(),
			staging_hash: blake2sum(&rmp_to_vec_all_named(&LwwMap::<Uuid, NodeRoleV>::new()).unwrap()[..]),
		};
		update_layout(&mut cl, &node_id_vec, &node_capacity_vec, &node_zone_vec);
		show_msg(&cl.calculate_partition_assignation(3,3).unwrap());
		assert!(cl.check());

		node_id_vec = vec![1, 2, 3, 4, 5, 6, 7, 8, 9];
		node_capacity_vec = vec![4000, 1000, 1000, 3000, 1000, 1000, 2000, 10000, 2000];
		node_zone_vec = vec!["A", "B", "C", "C", "C", "B", "G", "H", "I"]
			.into_iter()
			.map(|x| x.to_string())
			.collect();
		update_layout(&mut cl, &node_id_vec, &node_capacity_vec, &node_zone_vec);
		show_msg(&cl.calculate_partition_assignation(3,3).unwrap());
		assert!(cl.check());

		node_capacity_vec = vec![4000, 1000, 2000, 7000, 1000, 1000, 2000, 10000, 2000];
		update_layout(&mut cl, &node_id_vec, &node_capacity_vec, &node_zone_vec);
		show_msg(&cl.calculate_partition_assignation(3,3).unwrap());
		assert!(cl.check());

		node_capacity_vec = vec![4000000, 4000000, 2000000, 7000000, 1000000, 9000000, 2000000, 10000, 2000000];
		update_layout(&mut cl, &node_id_vec, &node_capacity_vec, &node_zone_vec);
		show_msg(&cl.calculate_partition_assignation(3,1).unwrap());
		assert!(cl.check());

	}
}