prosody
9dc34e1556d9
util/hashring.lua

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util/hashring.lua @ 10911:9dc34e1556d9

util.human.io.table: Allow a map callaback per column This allows e.g. mapping booleans to "yes" or "no", specific number formatting or generating virtual columns. All while not mutating the underlying data or creating additional temporary tables.
author Kim Alvefur <zash@zash.se>
date Thu, 04 Jun 2020 21:32:28 +0200
parent 10005:409ff72c501c
child 11208:96429946a742
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rev   line source
10005
409ff72c501c util.hashring: Implementation of hashring data structure
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1 local function generate_ring(nodes, num_replicas, hash)
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2 local new_ring = {};
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3 for _, node_name in ipairs(nodes) do
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4 for replica = 1, num_replicas do
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5 local replica_hash = hash(node_name..":"..replica);
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6 new_ring[replica_hash] = node_name;
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7 table.insert(new_ring, replica_hash);
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8 end
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9 end
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10 table.sort(new_ring);
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11 return new_ring;
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12 end
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13
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14 local hashring_methods = {};
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15 local hashring_mt = {
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16 __index = function (self, k)
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17 -- Automatically build self.ring if it's missing
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18 if k == "ring" then
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19 local ring = generate_ring(self.nodes, self.num_replicas, self.hash);
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20 rawset(self, "ring", ring);
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21 return ring;
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22 end
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23 return rawget(hashring_methods, k);
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24 end
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25 };
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26
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27 local function new(num_replicas, hash_function)
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28 return setmetatable({ nodes = {}, num_replicas = num_replicas, hash = hash_function }, hashring_mt);
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29 end;
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30
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31 function hashring_methods:add_node(name)
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32 self.ring = nil;
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33 self.nodes[name] = true;
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34 table.insert(self.nodes, name);
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35 return true;
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36 end
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37
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38 function hashring_methods:add_nodes(nodes)
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39 self.ring = nil;
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40 for _, node_name in ipairs(nodes) do
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41 if not self.nodes[node_name] then
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42 self.nodes[node_name] = true;
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43 table.insert(self.nodes, node_name);
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44 end
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45 end
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46 return true;
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47 end
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48
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49 function hashring_methods:remove_node(node_name)
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50 self.ring = nil;
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51 if self.nodes[node_name] then
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52 for i, stored_node_name in ipairs(self.nodes) do
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53 if node_name == stored_node_name then
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54 self.nodes[node_name] = nil;
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55 table.remove(self.nodes, i);
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56 return true;
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57 end
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58 end
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59 end
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60 return false;
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61 end
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62
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63 function hashring_methods:remove_nodes(nodes)
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64 self.ring = nil;
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65 for _, node_name in ipairs(nodes) do
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66 self:remove_node(node_name);
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67 end
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68 end
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69
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70 function hashring_methods:clone()
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71 local clone_hashring = new(self.num_replicas, self.hash);
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72 clone_hashring:add_nodes(self.nodes);
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73 return clone_hashring;
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74 end
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75
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76 function hashring_methods:get_node(key)
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77 local key_hash = self.hash(key);
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78 for _, replica_hash in ipairs(self.ring) do
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79 if key_hash < replica_hash then
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80 return self.ring[replica_hash];
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81 end
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82 end
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83 return self.ring[self.ring[1]];
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84 end
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85
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86 return {
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87 new = new;
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88 }