net.server_select: Better detection of errors for outgoing connections
On connection failure, a socket is marked readable and writable. So
to detect initial connection failures (connection refused, etc.) we
now watch for sockets becoming readable during initial connection,
and also read from readable sockets before writing to writable
sockets.
This should fix 'onconnect' being called for outgoing connections
that actually failed.
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;
}