File

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−local hashring = require "util.hashring";
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−
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−describe("util.hashring", function ()
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−	randomize(false);
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−
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−	local sha256 = require "util.hashes".sha256;
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−
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−	local ring = hashring.new(128, sha256);
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−
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−	it("should fail to get a node that does not exist", function ()
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−		assert.is_nil(ring:get_node("foo"))
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−	end);
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−
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−	it("should support adding nodes", function ()
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−		ring:add_node("node1");
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−	end);
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−
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−	it("should return a single node for all keys if only one node exists", function ()
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−		for i = 1, 100 do
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−			assert.is_equal("node1", ring:get_node(tostring(i)))
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−		end
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−	end);
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−
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−	it("should support adding a second node", function ()
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−		ring:add_node("node2");
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−	end);
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−
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−	it("should fail to remove a non-existent node", function ()
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−		assert.is_falsy(ring:remove_node("node3"));
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−	end);
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−
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−	it("should succeed to remove a node", function ()
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−		assert.is_truthy(ring:remove_node("node1"));
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−	end);
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−
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−	it("should return the only node for all keys", function ()
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−		for i = 1, 100 do
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−			assert.is_equal("node2", ring:get_node(tostring(i)))
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−		end
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−	end);
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−
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−	it("should support adding multiple nodes", function ()
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−		ring:add_nodes({ "node1", "node3", "node4", "node5" });
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−	end);
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−
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−	it("should disrupt a minimal number of keys on node removal", function ()
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−		local orig_ring = ring:clone();
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−		local node_tallies = {};
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−
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−		local n = 1000;
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−
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−		for i = 1, n do
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−			local key = tostring(i);
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−			local node = ring:get_node(key);
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−			node_tallies[node] = (node_tallies[node] or 0) + 1;
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−		end
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−
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−		--[[
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−		for node, key_count in pairs(node_tallies) do
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−			print(node, key_count, ("%.2f%%"):format((key_count/n)*100));
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−		end
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−		]]
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−
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−		ring:remove_node("node5");
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−
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−		local disrupted_keys = 0;
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−		for i = 1, n do
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−			local key = tostring(i);
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−			if orig_ring:get_node(key) ~= ring:get_node(key) then
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−				disrupted_keys = disrupted_keys + 1;
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−			end
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−		end
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−		assert.is_equal(node_tallies["node5"], disrupted_keys);
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−	end);
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−
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−	it("should support removing multiple nodes", function ()
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−		ring:remove_nodes({"node2", "node3", "node4", "node5"});
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−	end);
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−
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−	it("should return a single node for all keys if only one node remains", function ()
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−		for i = 1, 100 do
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−			assert.is_equal("node1", ring:get_node(tostring(i)))
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−		end
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−	end);
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−
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−	it("should support values associated with nodes", function ()
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−		local r = hashring.new(128, sha256);
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−		r:add_node("node1", { a = 1 });
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−		local node, value = r:get_node("foo");
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−		assert.is_equal("node1", node);
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−		assert.same({ a = 1 }, value);
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−	end);
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−end);