File

spec/util_hashring_spec.lua @ 13134:638f627e707f

util.datamanager: Add O(1) list indexing with on-disk index Index file contains offsets and lengths of each item() which allows seeking directly to each item and reading it without parsing the entire file. Also allows tricks like binary search, assuming items have some defined order. We take advantage of the 1-based indexing in tables to store a magic header in the 0 position, so that table index 1 ends up at file index 1.
author Kim Alvefur <zash@zash.se>
date Tue, 11 May 2021 02:09:56 +0200
parent 12795:87424cbedc55
line wrap: on
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local hashring = require "util.hashring";

describe("util.hashring", function ()
	randomize(false);

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

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

	it("should fail to get a node that does not exist", function ()
		assert.is_nil(ring:get_node("foo"))
	end);

	it("should support adding nodes", function ()
		ring:add_node("node1");
	end);

	it("should return a single node for all keys if only one node exists", function ()
		for i = 1, 100 do
			assert.is_equal("node1", ring:get_node(tostring(i)))
		end
	end);

	it("should support adding a second node", function ()
		ring:add_node("node2");
	end);

	it("should fail to remove a non-existent node", function ()
		assert.is_falsy(ring:remove_node("node3"));
	end);

	it("should succeed to remove a node", function ()
		assert.is_truthy(ring:remove_node("node1"));
	end);

	it("should return the only node for all keys", function ()
		for i = 1, 100 do
			assert.is_equal("node2", ring:get_node(tostring(i)))
		end
	end);

	it("should support adding multiple nodes", function ()
		ring:add_nodes({ "node1", "node3", "node4", "node5" });
	end);

	it("should disrupt a minimal number of keys on node removal", function ()
		local orig_ring = ring:clone();
		local node_tallies = {};

		local n = 1000;

		for i = 1, n do
			local key = tostring(i);
			local node = ring:get_node(key);
			node_tallies[node] = (node_tallies[node] or 0) + 1;
		end

		--[[
		for node, key_count in pairs(node_tallies) do
			print(node, key_count, ("%.2f%%"):format((key_count/n)*100));
		end
		]]

		ring:remove_node("node5");

		local disrupted_keys = 0;
		for i = 1, n do
			local key = tostring(i);
			if orig_ring:get_node(key) ~= ring:get_node(key) then
				disrupted_keys = disrupted_keys + 1;
			end
		end
		assert.is_equal(node_tallies["node5"], disrupted_keys);
	end);

	it("should support removing multiple nodes", function ()
		ring:remove_nodes({"node2", "node3", "node4", "node5"});
	end);

	it("should return a single node for all keys if only one node remains", function ()
		for i = 1, 100 do
			assert.is_equal("node1", ring:get_node(tostring(i)))
		end
	end);

	it("should support values associated with nodes", function ()
		local r = hashring.new(128, sha256);
		r:add_node("node1", { a = 1 });
		local node, value = r:get_node("foo");
		assert.is_equal("node1", node);
		assert.same({ a = 1 }, value);
	end);
end);