From 3bcebcae18b2ff547aadfb82cfcda74feaf6bf3f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?H=C3=A9ctor=20Molinero=20Fern=C3=A1ndez?=
<hector@molinero.dev>
Date: Wed, 9 Dec 2020 22:15:02 +0100
Subject: [PATCH] Transform Graphite tags into Prometheus labels
---
modules/http/prometheus.lua | 27 +++++++++++++++++++++++++--
1 file changed, 25 insertions(+), 2 deletions(-)
diff --git a/modules/http/prometheus.lua b/modules/http/prometheus.lua
index 68b491da5..094c5f4ed 100644
--- a/modules/http/prometheus.lua
+++ b/modules/http/prometheus.lua
@@ -102,7 +102,29 @@ local function serve_prometheus()
local latency = {}
local counter = '# TYPE %s counter\n%s %f'
for k,v in pairs(slist) do
- k = select(1, k:gsub('%.', '_'))
+ -- Transform Graphite tags into Prometheus labels
+ -- See: https://gitlab.nic.cz/knot/knot-resolver/-/issues/650
+ local k_index, k_len, k_tag = 0, #k, 0
+ k = select(1, k:gsub('.', function (c)
+ k_index = k_index + 1
+ if k_tag == 0 then
+ if c == '.' then return '_' end
+ if c == ';' then k_tag = 1; return '{' end
+ elseif k_tag == 1 then
+ if k_index == k_len then
+ if c == '=' then return '=""}'
+ else return c .. '"}' end
+ end
+ if c == '=' then k_tag = 2; return '="' end
+ elseif k_tag == 2 then
+ if k_index == k_len then
+ if c == ';' then return '"}'
+ else return c .. '"}' end
+ end
+ if c == ';' then k_tag = 1; return '",' end
+ end
+ return nil
+ end))
-- Aggregate histograms
local band = k:match('answer_([%d]+)ms')
if band then
@@ -112,7 +134,8 @@ local function serve_prometheus()
-- Counter as a fallback
else
local key = M.namespace .. k
- table.insert(render, string.format(counter, key, key, v))
+ local metric, label = key:match('^([^{]+)(.*)$')
+ table.insert(render, string.format(counter, metric, metric .. label, v))
end
end
-- Fill in latency histogram
--
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