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net.resolvers.service: Honour record 'weight' when picking SRV targets
#NotHappyEyeballs
This commit is contained in:
Matthew Wild
parent
d1c2e34e61
commit
d26811f5e5
2 changed files with 309 additions and 13 deletions
241
spec/net_resolvers_service_spec.lua
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241
spec/net_resolvers_service_spec.lua
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local set = require "util.set";
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insulate("net.resolvers.service", function ()
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local adns = {
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resolver = function ()
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return {
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lookup = function (_, cb, qname, qtype, qclass)
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if qname == "_xmpp-server._tcp.example.com"
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and (qtype or "SRV") == "SRV"
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and (qclass or "IN") == "IN" then
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cb({
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{ -- 60+35+60
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srv = { target = "xmpp0-a.example.com", port = 5228, priority = 0, weight = 60 };
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};
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{
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srv = { target = "xmpp0-b.example.com", port = 5216, priority = 0, weight = 35 };
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};
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{
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srv = { target = "xmpp0-c.example.com", port = 5200, priority = 0, weight = 0 };
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};
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{
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srv = { target = "xmpp0-d.example.com", port = 5256, priority = 0, weight = 120 };
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};
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{
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srv = { target = "xmpp1-a.example.com", port = 5273, priority = 1, weight = 30 };
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};
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{
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srv = { target = "xmpp1-b.example.com", port = 5274, priority = 1, weight = 30 };
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};
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{
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srv = { target = "xmpp2.example.com", port = 5275, priority = 2, weight = 0 };
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};
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});
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elseif qname == "_xmpp-server._tcp.single.example.com"
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and (qtype or "SRV") == "SRV"
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and (qclass or "IN") == "IN" then
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cb({
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{
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srv = { target = "xmpp0-a.example.com", port = 5269, priority = 0, weight = 0 };
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};
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});
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elseif qname == "_xmpp-server._tcp.half.example.com"
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and (qtype or "SRV") == "SRV"
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and (qclass or "IN") == "IN" then
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cb({
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{
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srv = { target = "xmpp0-a.example.com", port = 5269, priority = 0, weight = 0 };
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};
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{
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srv = { target = "xmpp0-b.example.com", port = 5270, priority = 0, weight = 1 };
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};
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});
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elseif qtype == "A" then
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local l = qname:match("%-(%a)%.example.com$") or "1";
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local d = ("%d"):format(l:byte())
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cb({
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{
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a = "127.0.0."..d;
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};
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});
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elseif qtype == "AAAA" then
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local l = qname:match("%-(%a)%.example.com$") or "1";
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local d = ("%04d"):format(l:byte())
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cb({
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{
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aaaa = "fdeb:9619:649e:c7d9::"..d;
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};
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});
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else
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cb(nil);
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end
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end;
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};
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end;
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};
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package.loaded["net.adns"] = mock(adns);
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local resolver = require "net.resolvers.service";
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math.randomseed(os.time());
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it("works for 99% of deployments", function ()
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-- Most deployments only have a single SRV record, let's make
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-- sure that works okay
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local expected_targets = set.new({
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-- xmpp0-a
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"tcp4 127.0.0.97 5269";
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"tcp6 fdeb:9619:649e:c7d9::0097 5269";
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});
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local received_targets = set.new({});
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local r = resolver.new("single.example.com", "xmpp-server");
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local done = false;
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local function handle_target(...)
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if ... == nil then
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done = true;
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-- No more targets
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return;
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end
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received_targets:add(table.concat({ ... }, " ", 1, 3));
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end
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r:next(handle_target);
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while not done do
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r:next(handle_target);
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end
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-- We should have received all expected targets, and no unexpected
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-- ones:
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assert.truthy(set.xor(received_targets, expected_targets):empty());
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end);
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it("supports A/AAAA fallback", function ()
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-- Many deployments don't have any SRV records, so we should
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-- fall back to A/AAAA records instead when that is the case
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local expected_targets = set.new({
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-- xmpp0-a
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"tcp4 127.0.0.97 5269";
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"tcp6 fdeb:9619:649e:c7d9::0097 5269";
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});
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local received_targets = set.new({});
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local r = resolver.new("xmpp0-a.example.com", "xmpp-server", "tcp", { default_port = 5269 });
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local done = false;
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local function handle_target(...)
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if ... == nil then
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done = true;
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-- No more targets
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return;
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end
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received_targets:add(table.concat({ ... }, " ", 1, 3));
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end
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r:next(handle_target);
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while not done do
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r:next(handle_target);
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end
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-- We should have received all expected targets, and no unexpected
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-- ones:
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assert.truthy(set.xor(received_targets, expected_targets):empty());
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end);
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it("works", function ()
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local expected_targets = set.new({
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-- xmpp0-a
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"tcp4 127.0.0.97 5228";
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"tcp6 fdeb:9619:649e:c7d9::0097 5228";
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"tcp4 127.0.0.97 5273";
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"tcp6 fdeb:9619:649e:c7d9::0097 5273";
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-- xmpp0-b
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"tcp4 127.0.0.98 5274";
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"tcp6 fdeb:9619:649e:c7d9::0098 5274";
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"tcp4 127.0.0.98 5216";
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"tcp6 fdeb:9619:649e:c7d9::0098 5216";
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-- xmpp0-c
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"tcp4 127.0.0.99 5200";
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"tcp6 fdeb:9619:649e:c7d9::0099 5200";
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-- xmpp0-d
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"tcp4 127.0.0.100 5256";
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"tcp6 fdeb:9619:649e:c7d9::0100 5256";
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-- xmpp2
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"tcp4 127.0.0.49 5275";
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"tcp6 fdeb:9619:649e:c7d9::0049 5275";
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});
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local received_targets = set.new({});
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local r = resolver.new("example.com", "xmpp-server");
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local done = false;
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local function handle_target(...)
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if ... == nil then
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done = true;
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-- No more targets
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return;
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end
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received_targets:add(table.concat({ ... }, " ", 1, 3));
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end
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r:next(handle_target);
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while not done do
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r:next(handle_target);
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end
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-- We should have received all expected targets, and no unexpected
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-- ones:
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assert.truthy(set.xor(received_targets, expected_targets):empty());
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end);
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it("balances across weights correctly #slow", function ()
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-- This mimics many repeated connections to 'example.com' (mock
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-- records defined above), and records the port number of the
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-- first target. Therefore it (should) only return priority
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-- 0 records, and the input data is constructed such that the
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-- last two digits of the port number represent the percentage
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-- of times that record should (on average) be picked first.
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-- To prevent random test failures, we test across a handful
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-- of fixed (randomly selected) seeds.
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for _, seed in ipairs({ 8401877, 3943829, 7830992 }) do
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math.randomseed(seed);
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local results = {};
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local function run()
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local run_results = {};
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local r = resolver.new("example.com", "xmpp-server");
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local function record_target(...)
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if ... == nil then
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-- No more targets
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return;
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end
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run_results = { ... };
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end
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r:next(record_target);
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return run_results[3];
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end
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for _ = 1, 1000 do
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local port = run();
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results[port] = (results[port] or 0) + 1;
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end
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local ports = {};
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for port in pairs(results) do
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table.insert(ports, port);
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end
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table.sort(ports);
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for _, port in ipairs(ports) do
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--print("PORT", port, tostring((results[port]/1000) * 100).."% hits (expected "..tostring(port-5200).."%)");
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local hit_pct = (results[port]/1000) * 100;
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local expected_pct = port - 5200;
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--print(hit_pct, expected_pct, math.abs(hit_pct - expected_pct));
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assert.is_true(math.abs(hit_pct - expected_pct) < 5);
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end
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--print("---");
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end
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end);
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end);
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