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local t_sort = table.sort
local m_floor = math.floor;
local time = require "socket".gettime;
local function nop_function() end
local function percentile(arr, length, pc)
local n = pc/100 * (length + 1);
local k, d = m_floor(n), n%1;
if k == 0 then
return arr[1];
elseif k >= length then
return arr[length];
end
return arr[k] + d*(arr[k+1] - arr[k]);
end
local function new_registry(config)
config = config or {};
local duration_sample_interval = config.duration_sample_interval or 5;
local duration_max_samples = config.duration_max_stored_samples or 5000;
local registry = {};
local methods;
methods = {
amount = function (name, initial)
local v = initial or 0;
registry[name] = function () return "amount", v; end
return function (new_v) v = new_v; end
end;
counter = function (name, initial)
local v = initial or 0;
registry[name] = function () return "amount", v; end
return function (delta)
v = v + delta;
end;
end;
rate = function (name)
local since, n = time(), 0;
registry[name] = function ()
local t = time();
local stats = {
rate = n/(t-since);
count = n;
};
since, n = t, 0;
return "rate", stats.rate, stats;
end;
return function ()
n = n + 1;
end;
end;
duration = function (name)
local events, last_event = {}, 0;
local n_actual_events = 0;
local since = time();
registry[name] = function ()
local n_stored_events = #events;
t_sort(events);
local sum = 0;
for i = 1, n_stored_events do
sum = sum + events[i];
end
local new_time = time();
local stats = {
samples = events;
sample_count = n_stored_events;
count = n_actual_events,
rate = n_actual_events/(new_time-since);
average = n_stored_events > 0 and sum/n_stored_events or 0,
min = events[1],
max = events[n_stored_events],
};
events, last_event = {}, 0;
n_actual_events = 0;
since = new_time;
return "duration", stats.average, stats;
end;
return function ()
n_actual_events = n_actual_events + 1;
if n_actual_events%duration_sample_interval > 0 then
return nop_function;
end
local start_time = time();
return function ()
local end_time = time();
local duration = end_time - start_time;
last_event = (last_event%duration_max_samples) + 1;
events[last_event] = duration;
end
end;
end;
get_stats = function ()
return registry;
end;
};
return methods;
end
return {
new = new_registry;
get_histogram = function (duration, n_buckets)
n_buckets = n_buckets or 100;
local events, n_events = duration.samples, duration.sample_count;
if not (events and n_events) then
return nil, "not a valid duration stat";
end
local histogram = {};
for i = 1, 100, 100/n_buckets do
histogram[i] = percentile(events, n_events, i);
end
return histogram;
end;
get_percentile = function (duration, pc)
local events, n_events = duration.samples, duration.sample_count;
if not (events and n_events) then
return nil, "not a valid duration stat";
end
return percentile(events, n_events, pc);
end;
}
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