Move transform step to a separate function

diff --git a/modules/http/prometheus.lua b/modules/http/prometheus.lua
index 094c5f4edd9e320148568fbedfc76b2114538403..3218552fb992dba49693a2a02cbdd1e87517504d 100644 (file)
--- a/modules/http/prometheus.lua
+++ b/modules/http/prometheus.lua
@@ -95,6 +95,35 @@ local function stream_stats(_, ws)
        end
 end
 
+-- Transform metrics from Graphite to Prometheus format
+-- See: https://gitlab.nic.cz/knot/knot-resolver/-/issues/650
+-- E.g.:
+--  worker.ipv4 -> worker_ipv4
+--  answer.blocked;stype=A -> answer_blocked{stype="A"}
+local function get_metric(key)
+       local key_index, key_len, key_tag = 0, #key, 0
+       return select(1, key:gsub('.', function (c)
+               key_index = key_index + 1
+               if key_tag == 0 then
+                       if c == '.' then return '_' end
+                       if c == ';' then key_tag = 1; return '{' end
+               elseif key_tag == 1 then
+                       if key_index == key_len then
+                               if c == '=' then return '=""}'
+                               else return c .. '"}' end
+                       end
+                       if c == '=' then key_tag = 2; return '="' end
+               elseif key_tag == 2 then
+                       if key_index == key_len then
+                               if c == ';' then return '"}'
+                               else return c .. '"}' end
+                       end
+                       if c == ';' then key_tag = 1; return '",' end
+               end
+               return nil
+       end))
+end
+
 -- Render stats in Prometheus text format
 local function serve_prometheus()
        -- First aggregate metrics list and print counters
@@ -102,29 +131,7 @@ local function serve_prometheus()
        local latency = {}
        local counter = '# TYPE %s counter\n%s %f'
        for k,v in pairs(slist) do
-               -- 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))
+               k = get_metric(k)
                -- Aggregate histograms
                local band = k:match('answer_([%d]+)ms')
                if band then
@@ -134,8 +141,8 @@ local function serve_prometheus()
                -- Counter as a fallback
                else
                        local key = M.namespace .. k
-                       local metric, label = key:match('^([^{]+)(.*)$')
-                       table.insert(render, string.format(counter, metric, metric .. label, v))
+                       local name, label = key:match('^([^{]+)(.*)$')
+                       table.insert(render, string.format(counter, name, name .. label, v))
                end
        end
        -- Fill in latency histogram