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-rw-r--r--util/statistics.lua160
1 files changed, 160 insertions, 0 deletions
diff --git a/util/statistics.lua b/util/statistics.lua
new file mode 100644
index 00000000..39954652
--- /dev/null
+++ b/util/statistics.lua
@@ -0,0 +1,160 @@
+local t_sort = table.sort
+local m_floor = math.floor;
+local time = require "util.time".now;
+
+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] or 0;
+ 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 function get_distribution_stats(events, n_actual_events, since, new_time, units)
+ local n_stored_events = #events;
+ t_sort(events);
+ local sum = 0;
+ for i = 1, n_stored_events do
+ sum = sum + events[i];
+ end
+
+ return {
+ 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] or 0,
+ max = events[n_stored_events] or 0,
+ units = units,
+ };
+ end
+
+
+ local registry = {};
+ local methods;
+ methods = {
+ amount = function (name, initial)
+ local v = initial or 0;
+ registry[name..":amount"] = 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..":amount"] = function () return "amount", v; end
+ return function (delta)
+ v = v + delta;
+ end;
+ end;
+ rate = function (name)
+ local since, n = time(), 0;
+ registry[name..":rate"] = 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;
+ distribution = function (name, unit, type)
+ type = type or "distribution";
+ local events, last_event = {}, 0;
+ local n_actual_events = 0;
+ local since = time();
+
+ registry[name..":"..type] = function ()
+ local new_time = time();
+ local stats = get_distribution_stats(events, n_actual_events, since, new_time, unit);
+ events, last_event = {}, 0;
+ n_actual_events = 0;
+ since = new_time;
+ return type, stats.average, stats;
+ end;
+
+ return function (value)
+ n_actual_events = n_actual_events + 1;
+ if n_actual_events%duration_sample_interval == 1 then
+ last_event = (last_event%duration_max_samples) + 1;
+ events[last_event] = value;
+ end
+ end;
+ end;
+ sizes = function (name)
+ return methods.distribution(name, "bytes", "size");
+ end;
+ times = function (name)
+ local events, last_event = {}, 0;
+ local n_actual_events = 0;
+ local since = time();
+
+ registry[name..":duration"] = function ()
+ local new_time = time();
+ local stats = get_distribution_stats(events, n_actual_events, since, new_time, "seconds");
+ 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 ~= 1 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 distribution 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 distribution stat";
+ end
+ return percentile(events, n_events, pc);
+ end;
+}