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Remove size limit for per-metric lookup tables
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Size based cleanup was added to avoid unbounded growth of lookup tables
as metrics get deleted/reset. This should not be necessary now when lookup
tables are being reset on metric deletion.

This reverts eb1876d
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knyar committed Apr 17, 2024
1 parent f7c83a1 commit b9efa64
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Showing 3 changed files with 3 additions and 68 deletions.
6 changes: 0 additions & 6 deletions README.md
Original file line number Diff line number Diff line change
Expand Up @@ -106,12 +106,6 @@ section of nginx configuration.
* `sync_interval` (number): sets the sync interval for per-worker counters and
key index (in seconds). This sets the boundary on eventual consistency of
counter metric increments, and metric resets/deletions. Defaults to 1.
* `lookup_max_size` (number): maximum size of a per-metric lookup table
maintained by each worker to cache full metric names. Defaults to 1000.
If you have metrics with extremely high cardinality and lots of available
RAM, you might want to increase this to avoid cache getting flushed too
often. Decreasing this makes sense if you have a very large number of
metrics or need to minimize memory usage of this library.

Returns a `prometheus` object that should be used to register metrics.

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27 changes: 3 additions & 24 deletions prometheus.lua
Original file line number Diff line number Diff line change
Expand Up @@ -92,9 +92,6 @@ local DEFAULT_ERROR_METRIC_NAME = "nginx_metric_errors_total"
-- Default value for per-worker counter sync interval (seconds).
local DEFAULT_SYNC_INTERVAL = 1

-- Default max size of lookup table
local DEFAULT_LOOKUP_MAX_SIZE = 1000

-- Default set of latency buckets, 5ms to 10s:
local DEFAULT_BUCKETS = {0.005, 0.01, 0.02, 0.03, 0.05, 0.075, 0.1, 0.2, 0.3,
0.4, 0.5, 0.75, 1, 1.5, 2, 3, 4, 5, 10}
Expand Down Expand Up @@ -383,10 +380,6 @@ local function lookup_or_create(self, label_values)
self.name, self.label_count, cnt, table_to_string(label_values))
end

if self.lookup_size >= self.lookup_max_size then
self:reset_lookup()
end

local t = self.lookup
if label_values then
-- Don't use ipairs here to avoid inner loop generates trace first
Expand Down Expand Up @@ -444,8 +437,6 @@ local function lookup_or_create(self, label_values)
end
t[LEAF_KEY] = full_name

self.lookup_size = self.lookup_size + 1

local err = self._key_index:add(full_name, ERR_MSG_LRU_EVICTION)
if err then
return nil, err
Expand Down Expand Up @@ -622,12 +613,6 @@ local function observe(self, value, label_values)
end
end

-- Reset the metric name lookup table for a given metric.
local function reset_lookup(self)
self.lookup_size = 0
self.lookup = {}
end

-- Delete all metrics for a given gauge, counter or a histogram.
--
-- This is like `del`, but will delete all time series for all previously
Expand Down Expand Up @@ -696,7 +681,7 @@ local function reset(self)
end

-- Clean up the full metric name lookup table as well.
self:reset_lookup()
self.lookup = {}
end

-- Initialize the module.
Expand Down Expand Up @@ -733,13 +718,10 @@ function Prometheus.init(dict_name, options_or_prefix)
DEFAULT_ERROR_METRIC_NAME
self.sync_interval = options_or_prefix.sync_interval or
DEFAULT_SYNC_INTERVAL
self.lookup_max_size = options_or_prefix.lookup_max_size or
DEFAULT_LOOKUP_MAX_SIZE
else
self.prefix = options_or_prefix or ''
self.error_metric_name = DEFAULT_ERROR_METRIC_NAME
self.sync_interval = DEFAULT_SYNC_INTERVAL
self.lookup_max_size = DEFAULT_LOOKUP_MAX_SIZE
end

self.registry = {}
Expand All @@ -749,14 +731,14 @@ function Prometheus.init(dict_name, options_or_prefix)
local metric_name = ngx_re_gsub(metric_key, "{.*", "", "jo")
if self.registry[metric_name] then
local m = self.registry[metric_name]
m:reset_lookup()
m.lookup = {}
return
end

metric_name = ngx_re_gsub(metric_name, "_sum$", "", "jo")
local m = self.registry[metric_name]
if m and m.typ == TYPE_HISTOGRAM then
m:reset_lookup()
m.lookup = {}
end
end)

Expand Down Expand Up @@ -866,9 +848,6 @@ local function register(self, name, help, label_names, buckets, typ)
-- ['my.net']['200'][LEAF_KEY] = 'http_count{host="my.net",status="200"}'
-- ['my.net']['500'][LEAF_KEY] = 'http_count{host="my.net",status="500"}'
lookup = {},
lookup_size = 0,
lookup_max_size = self.lookup_max_size,
reset_lookup = reset_lookup,
parent = self,
-- Store a reference for logging functions for faster lookup.
_log_error = function(...) self:log_error(...) end,
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38 changes: 0 additions & 38 deletions prometheus_test.lua
Original file line number Diff line number Diff line change
Expand Up @@ -849,44 +849,6 @@ function TestKeyIndex:testSync()
luaunit.assertEquals(self.last_deleted_key, "key2")
end

function TestPrometheus:testLookupMaxSize()
local c = self.p:counter("testc", "Counter", {"tag"})
local g = self.p:gauge("testg", "Gauge", {"tag"})
local h = self.p:histogram("testh", "Histogram", {"tag"})

luaunit.assertEquals(c.lookup_size, 0)
luaunit.assertEquals(g.lookup_size, 0)
luaunit.assertEquals(h.lookup_size, 0)
luaunit.assertEquals(c.lookup_max_size, 1000)
luaunit.assertEquals(g.lookup_max_size, 1000)
luaunit.assertEquals(h.lookup_max_size, 1000)

for _, max_size in ipairs({10, 17, 101}) do
local p1 = require('prometheus').init("metrics",
{lookup_max_size=max_size})
local c1 = p1:counter("testc1", "Counter", {"tag"})
local g1 = p1:gauge("testg1", "Gauge", {"tag"})
local h1 = p1:histogram("testh1", "Histogram", {"tag"})

luaunit.assertEquals(p1.lookup_max_size, max_size)
luaunit.assertEquals(c1.lookup_max_size, max_size)
luaunit.assertEquals(g1.lookup_max_size, max_size)
luaunit.assertEquals(h1.lookup_max_size, max_size)

for i = 0, max_size * 2.1, 1 do
c1:inc(1, {tostring(i)})
g1:set(3, {tostring(i)})
h1:observe(50, {tostring(i)})

luaunit.assertEquals(c1.lookup_size, (i % max_size)+1)
luaunit.assertEquals(g1.lookup_size, (i % max_size)+1)
luaunit.assertEquals(h1.lookup_size, (i % max_size)+1)
end
end

luaunit.assertEquals(self.dict:get("nginx_metric_errors_total"), 0)
end

function TestPrometheus.testPrintfTable()
local p = require('prometheus')
luaunit.assertEquals(p._table_to_string(nil), "nil")
Expand Down

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