1 local hashring = require "util.hashring";

     2 

     3 describe("util.hashring", function ()

     4 

     5 	local sha256 = require "util.hashes".sha256;

     6 

     7 	local ring = hashring.new(128, sha256);

     8 

     9 	it("should fail to get a node that does not exist", function ()

    10 		assert.is_nil(ring:get_node("foo"))

    11 	end);

    12 

    13 	it("should support adding nodes", function ()

    14 		ring:add_node("node1");

    15 	end);

    16 

    17 	it("should return a single node for all keys if only one node exists", function ()

    18 		for i = 1, 100 do

    19 			assert.is_equal("node1", ring:get_node(tostring(i)))

    20 		end

    21 	end);

    22 

    23 	it("should support adding a second node", function ()

    24 		ring:add_node("node2");

    25 	end);

    26 

    27 	it("should fail to remove a non-existent node", function ()

    28 		assert.is_falsy(ring:remove_node("node3"));

    29 	end);

    30 

    31 	it("should succeed to remove a node", function ()

    32 		assert.is_truthy(ring:remove_node("node1"));

    33 	end);

    34 

    35 	it("should return the only node for all keys", function ()

    36 		for i = 1, 100 do

    37 			assert.is_equal("node2", ring:get_node(tostring(i)))

    38 		end

    39 	end);

    40 

    41 	it("should support adding multiple nodes", function ()

    42 		ring:add_nodes({ "node1", "node3", "node4", "node5" });

    43 	end);

    44 

    45 	it("should disrupt a minimal number of keys on node removal", function ()

    46 		local orig_ring = ring:clone();

    47 		local node_tallies = {};

    48 

    49 		local n = 1000;

    50 

    51 		for i = 1, n do

    52 			local key = tostring(i);

    53 			local node = ring:get_node(key);

    54 			node_tallies[node] = (node_tallies[node] or 0) + 1;

    55 		end

    56 

    57 		--[[

    58 		for node, key_count in pairs(node_tallies) do

    59 			print(node, key_count, ("%.2f%%"):format((key_count/n)*100));

    60 		end

    61 		]]

    62 

    63 		ring:remove_node("node5");

    64 

    65 		local disrupted_keys = 0;

    66 		for i = 1, n do

    67 			local key = tostring(i);

    68 			if orig_ring:get_node(key) ~= ring:get_node(key) then

    69 				disrupted_keys = disrupted_keys + 1;

    70 			end

    71 		end

    72 		assert.is_equal(node_tallies["node5"], disrupted_keys);

    73 	end);

    74 

    75 	it("should support removing multiple nodes", function ()

    76 		ring:remove_nodes({"node2", "node3", "node4", "node5"});

    77 	end);

    78 

    79 	it("should return a single node for all keys if only one node remains", function ()

    80 		for i = 1, 100 do

    81 			assert.is_equal("node1", ring:get_node(tostring(i)))

    82 		end

    83 	end);

    84 

    85 end);