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local time = require "util.time".now;
local new_metric_registry = require "util.openmetrics".new_metric_registry;
local render_histogram_le = require "util.openmetrics".render_histogram_le;
-- BEGIN of Metric implementations
-- Gauges
local gauge_metric_mt = {}
gauge_metric_mt.__index = gauge_metric_mt
local function new_gauge_metric()
local metric = { value = 0 }
setmetatable(metric, gauge_metric_mt)
return metric
end
function gauge_metric_mt:set(value)
self.value = value
end
function gauge_metric_mt:add(delta)
self.value = self.value + delta
end
function gauge_metric_mt:reset()
self.value = 0
end
function gauge_metric_mt:iter_samples()
local done = false
return function(_s)
if done then
return nil, true
end
done = true
return "", nil, _s.value
end, self
end
-- Counters
local counter_metric_mt = {}
counter_metric_mt.__index = counter_metric_mt
local function new_counter_metric()
local metric = {
_created = time(),
value = 0,
}
setmetatable(metric, counter_metric_mt)
return metric
end
function counter_metric_mt:set(value)
self.value = value
end
function counter_metric_mt:add(value)
self.value = (self.value or 0) + value
end
function counter_metric_mt:iter_samples()
local step = 0
return function(_s)
step = step + 1
if step == 1 then
return "_created", nil, _s._created
elseif step == 2 then
return "_total", nil, _s.value
else
return nil, nil, true
end
end, self
end
function counter_metric_mt:reset()
self.value = 0
end
-- Histograms
local histogram_metric_mt = {}
histogram_metric_mt.__index = histogram_metric_mt
local function new_histogram_metric(buckets)
local metric = {
_created = time(),
_sum = 0,
_count = 0,
}
-- the order of buckets matters unfortunately, so we cannot directly use
-- the thresholds as table keys
for i, threshold in ipairs(buckets) do
metric[i] = {
threshold = threshold,
threshold_s = render_histogram_le(threshold),
count = 0
}
end
setmetatable(metric, histogram_metric_mt)
return metric
end
function histogram_metric_mt:sample(value)
-- According to the I-D, values must be part of all buckets
for i, bucket in pairs(self) do
if "number" == type(i) and bucket.threshold >= value then
bucket.count = bucket.count + 1
end
end
self._sum = self._sum + value
self._count = self._count + 1
end
function histogram_metric_mt:iter_samples()
local key = nil
return function (_s)
local data
key, data = next(_s, key)
if key == "_created" or key == "_sum" or key == "_count" then
return key, nil, data
elseif key ~= nil then
return "_bucket", {["le"] = data.threshold_s}, data.count
else
return nil, nil, nil
end
end, self
end
function histogram_metric_mt:reset()
self._created = time()
self._count = 0
self._sum = 0
for i, bucket in pairs(self) do
if "number" == type(i) then
bucket.count = 0
end
end
end
-- Summary
local summary_metric_mt = {}
summary_metric_mt.__index = summary_metric_mt
local function new_summary_metric()
-- quantiles are not supported yet
local metric = {
_created = time(),
_sum = 0,
_count = 0,
}
setmetatable(metric, summary_metric_mt)
return metric
end
function summary_metric_mt:sample(value)
self._sum = self._sum + value
self._count = self._count + 1
end
function summary_metric_mt:iter_samples()
local key = nil
return function (_s)
local data
key, data = next(_s, key)
return key, nil, data
end, self
end
function summary_metric_mt:reset()
self._created = time()
self._count = 0
self._sum = 0
end
local pull_backend = {
gauge = new_gauge_metric,
counter = new_counter_metric,
histogram = new_histogram_metric,
summary = new_summary_metric,
}
-- END of Metric implementations
local function new()
return {
metric_registry = new_metric_registry(pull_backend),
}
end
return {
new = new;
}
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