Next-generation lagometer as a weighted histogram
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Aaron Suen
parent
9ce18fd427
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d54230df66
@ -1,14 +1,21 @@
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------------------------------------------------------------------------
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Display a simple HUD meter showing an estimate of current server "lag,"
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i.e. the size of "steps" the server is running. This allows admins to
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monitor system performance, or mod authors to monitor code performance
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impact, continuously, instead of having to do /status over and over.
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Display a full near-realtime analysis of server "lag", i.e. globalstep
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dtimes. This allows admins to monitor system performance, or mod
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authors to monitor code performance impact, continuously, instead of
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having to do /status over and over.
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The lag calculation is done indepdendently of /status's max_lag, and
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some parameters can be tuned. See init.lua for configuration details.
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The visualization is a weighted histogram, where time is sorted into
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buckets by step size, and each bucket contains the total amount of time
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spent performing steps of that size. The number on the right is the
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step size (max) for that bucket, the number on the left is the total
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time in that bucket, and the bar graph visually approximates (up to a
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limit) the time value. Instead of just an average, this visualization
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shows distribution of step sizes, making it possible to identify
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specific types of spikes.
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Players will see the lagometer iff they have the "lagometer" priv.
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The meter displays just above the health bar.
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Players will see the lagometer if they have the "lagometer" priv, and
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enable the lagometer toggle via the /lagometer command. The meter
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displays on the bottom right of the screen.
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------------------------------------------------------------------------
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@ -1,33 +1,83 @@
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-- LUALOCALS < ---------------------------------------------------------
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local ipairs, minetest, string, tonumber
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= ipairs, minetest, string, tonumber
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local string_format
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= string.format
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local ipairs, loadstring, math, minetest, pairs, string, tonumber
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= ipairs, loadstring, math, minetest, pairs, string, tonumber
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local math_ceil, math_floor, string_format, string_rep, string_sub
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= math.ceil, math.floor, string.format, string.rep, string.sub
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-- LUALOCALS > ---------------------------------------------------------
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local modname = minetest.get_current_modname()
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------------------------------------------------------------------------
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-- SETTINGS
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local function getconf(suff)
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return tonumber(minetest.settings:get(modname .. "_" .. suff))
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end
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-- How often to publish updates to players. Too infrequent and the meter
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-- is no longer as "real-time", but too frequent and they'll get bombarded
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-- with HUD change packets.
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local interval = tonumber(minetest.settings:get(modname .. "_interval")) or 2
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-- is no longer as "real-time", but too frequent and they'll get
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-- bombarded with HUD change packets.
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local interval = getconf("interval") or 2
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-- The "fall-off ratio" to multiply the previous lag values by each tick.
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-- Lag spikes will set the lag estimate high, and multiplying by this fall-off
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-- ratio is the only way it will fall back down.
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local falloff = tonumber(minetest.settings:get(modname .. "_falloff")) or 0.99
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-- The amount of time in each measurement period. This is also the
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-- amount of time between each period expiration.
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local period_length = getconf("period_length") or 5
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-- Keep track of our estimate of server lag.
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local lag = 0
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-- The number of time periods across which to accumualate statistics.
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local period_count = getconf("period_count") or 12
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-- Keep track of connected players and their meters.
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local meters = {}
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-- Size of buckets into which dtime values are sorted in weighted
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-- histogram.
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local bucket_step = getconf("bucket_step") or 0.05
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-- Maximum number of buckets. All step times too large for any other
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-- bucket will go into the highest bucket.
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local bucket_max = getconf("bucket_max") or 20
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-- Constructor function to pre-initialize a new period table.
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local newperiod = loadstring("return {" .. string_rep("0,", bucket_max) .. "}")
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------------------------------------------------------------------------
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-- MEASUREMENT
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-- Queue of accounting periods.
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local periods = {}
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-- Precise game runtime clock.
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local clock = 0
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-- Collect statistics at each step.
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minetest.register_globalstep(function(dtime)
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-- Update clock.
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clock = clock + dtime
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-- Find current accounting period, initialize
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-- if not already present.
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local key = math_floor(clock / period_length)
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local cur = periods[key]
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if not cur then
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cur = newperiod()
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periods[key] = cur
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end
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-- Find correct histogram bucket.
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local bucket = math_floor(dtime / bucket_step)
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if bucket > bucket_max then bucket = bucket_max
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elseif bucket < 1 then bucket = 1 end
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-- Add weight to bucket.
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cur[bucket] = cur[bucket] + dtime
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end)
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------------------------------------------------------------------------
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-- USER TOGGLE
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-- Create a separate privilege for players to see the lagometer. This
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-- feature is too "internal" to show to all players unconditionally,
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-- but not so "internal" that it should depend on the "server" priv.
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minetest.register_privilege("lagometer", "Can see the lagometer")
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-- Command to manually toggle the lagometer.
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minetest.register_chatcommand("lagometer", {
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description = "Toggle the lagometer",
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privs = {lagometer = true},
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@ -42,52 +92,82 @@ minetest.register_chatcommand("lagometer", {
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end,
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})
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------------------------------------------------------------------------
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-- REPORTING
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-- Keep track of connected players and their meters.
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local meters = {}
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-- Pre-allocated bar graph.
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local graphbar = string_rep("|", 40)
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-- Function to publish current lag values to all receiving parties.
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local function publish()
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-- Format the lag string with the raw numerical value, and
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-- a cheapo ASCII "bar graph" to provide a better visual cue
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-- for its general magnitude.
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local t = string_format("Server Lag: %2.2f ", lag)
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local q = lag * 10 + 0.5
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if q > 40 then q = 40 end
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for _ = 1, q, 1 do t = t .. "|" end
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-- Expire old periods, and accumulate current ones.
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local accum = newperiod()
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do
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local curkey = math_floor(clock / period_length)
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for pk, pv in pairs(periods) do
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if pk <= curkey - period_count then
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periods[pk] = nil
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else
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for ik, iv in ipairs(pv) do
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accum[ik] = accum[ik] + iv
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end
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end
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end
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end
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-- Apply the appropriate text to each meter.
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for _, p in ipairs(minetest.get_connected_players()) do
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local n = p:get_player_name()
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local v = meters[n]
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-- Construct the weighted historgram visualization.
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for bucket = 1, bucket_max do
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local qty = accum[bucket]
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-- Players with privilege will see the meter, players without
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-- will get an empty string. The meters are always left in place
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-- rather than added/removed for simplicity, and to make it easier
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-- to handle when the priv is granted/revoked while the player
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-- is connected.
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local s = ""
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if minetest.get_player_privs(n).lagometer
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and (p:get_meta():get_string("lagometer") or "") ~= ""
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then s = t end
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local line = qty <= 0 and "" or string_format(" % 2.2f % s % 2.2f % s", qty,
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string_sub(graphbar, 1, math_ceil(qty * 2)),
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bucket * bucket_step,
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string_rep("\n", bucket - 1))
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-- Only apply the text if it's changed, to minimize the risk of
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-- generating useless unnecessary packets.
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if s ~= "" and not v then
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meters[n] = {
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text = s,
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hud = p:hud_add({
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hud_elem_type = "text",
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position = {x = 0.5, y = 1},
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text = s,
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alignment = {x = 1, y = -1},
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number = 0xC0C0C0,
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scale = {x = 1280, y = 20},
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offset = {x = -262, y = -88}
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})
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}
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elseif v and s == "" then
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p:hud_remove(v.hud)
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meters[n] = nil
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elseif v and v.text ~= s then
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p:hud_change(v.hud, "text", s)
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v.text = s
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-- Apply the appropriate text to each meter.
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for _, player in ipairs(minetest.get_connected_players()) do
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local pname = player:get_player_name()
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local meter = meters[pname]
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if not meter then
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meter = {}
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meters[pname] = meter
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end
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local mline = meter[bucket]
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-- Players with privilege will see the meter, players without
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-- will get an empty string. The meters are always left in place
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-- rather than added/removed for simplicity, and to make it easier
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-- to handle when the priv is granted/revoked while the player
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-- is connected.
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local text = ""
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if minetest.get_player_privs(pname).lagometer
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and (player:get_meta():get_string("lagometer") or "") ~= ""
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then text = line end
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-- Only apply the text if it's changed, to minimize the risk of
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-- generating useless unnecessary packets.
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if text ~= "" and not mline then
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meter[bucket] = {
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text = text,
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hud = player:hud_add({
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hud_elem_type = "text",
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position = {x = 1, y = 1},
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text = text,
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alignment = {x = -1, y = -1},
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number = 0xC0C0C0,
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offset = {x = -4, y = -4}
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})
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}
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elseif mline and text == "" then
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player:hud_remove(mline.hud)
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meter[bucket] = nil
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elseif mline and mline.text ~= text then
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player:hud_change(mline.hud, "text", text)
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mline.text = text
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end
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end
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end
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end
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@ -100,17 +180,6 @@ local function update()
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end
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minetest.after(0, update)
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-- Do the lag estimate work in a globalstep. If the lag spikes
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-- up, publish immediately; if not, allow the timer to publish as
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-- it falls off.
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minetest.register_globalstep(function(dtime)
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lag = lag * falloff
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if dtime > lag then
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lag = dtime
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publish()
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end
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end)
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-- Remove meter registrations when players leave.
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minetest.register_on_leaveplayer(function(player)
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meters[player:get_player_name()] = nil
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