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spec/util_hashring_spec.lua @ 10973:39991e40d1dc
util.dbuffer: dynamic string buffer
Similar to util.ringbuffer (and shares almost identical API). Differences:
- size limit is optional and dynamic
- does not allocate a fixed buffer of max_size bytes
- focus on simply storing references to existing string objects where possible,
avoiding unnecessary allocations
- references are still stored in a ring buffer to enable use as a fast FIFO
Optional second parameter to new() provides the number of ring buffer segments. On
Lua 5.2 on my laptop, a segment is ~19 bytes. If the ring buffer fills up, the next
write will compact all strings into a single item.
author | Matthew Wild <mwild1@gmail.com> |
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date | Fri, 26 Jun 2020 16:41:31 +0100 |
parent | 10007:de43ca319184 |
child | 12794:249b01adc54a |
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local hashring = require "util.hashring"; describe("util.hashring", function () 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); end);