feat: remove leading and trailing zeros

prometheus.lua

@@ -22,9 +22,8 @@
 --    used when labels were declared). "le" label for histogram metrics always
 --    goes last;
 --  * bucket boundaries (which are exposed as values of the "le" label) are
---    presented as floating point numbers with leading and trailing zeroes.
---    Number of of zeroes is determined for each bucketer automatically based on
---    bucket boundaries;
+--    stored as floating point numbers with leading and trailing zeroes,
+--    and those zeros would be removed just before we expose the metrics;
 --  * internally "+Inf" bucket is stored as "Inf" (to make it appear after
 --    all numeric buckets), and gets replaced by "+Inf" just before we
 --    expose the metrics.
@@ -40,7 +39,14 @@
 --   m1_count{site="site1"}
 --   m1_sum{site="site1"}
 --
--- "Inf" will be replaced by "+Inf" while publishing metrics.
+-- And when expose, it would change to:
+--
+--   m1_bucket{site="site1",le="0.00005"}
+--   m1_bucket{site="site1",le="10"}
+--   m1_bucket{site="site1",le="1000"}
+--   m1_bucket{site="site1",le="+Inf"}
+--   m1_count{site="site1"}
+--   m1_sum{site="site1"}
 --
 -- You can find the latest version and documentation at
 -- https://github.com/knyar/nginx-lua-prometheus
@@ -261,6 +267,36 @@ local function construct_bucket_format(buckets)
   return "%0" .. (max_order + max_precision + 1) .. "." .. max_precision .. "f"
 end
 
+-- Format bucket format when expose metrics.
+--
+-- This receives a key, remove leading and trailing zeros and return the cleaner
+-- number, in order to make the output more clear, without effect on the increasing
+-- order.
+--
+-- Args:
+--   key: the metric key
+--
+-- Returns:
+--   (string) the formatted key
+local function format_bucket_when_expose(key)
+  local part1, bucket, part2 = key:match('(.*[,{]le=")(.*)(".*)')
+  if part1 == nil then
+    return key
+  end
+
+  if bucket == "Inf" then
+    return table.concat({part1, "+Inf", part2})
+  else
+    bucket = tostring(tonumber(bucket))
+    -- In lua5.3 when decimal part is zero, tonumber would not turn float to int like <5.3,
+    -- rather it would leave '.0' at the end. So trim it here.
+    if (bucket:sub(-2, -1) == ".0") then
+      bucket = bucket:sub(1, -3)
+    end
+    return table.concat({part1, bucket, part2})
+  end
+end
+
 -- Return a full metric name for a given metric+label combination.
 --
 -- This function calculates a full metric name (or, in case of a histogram
@@ -806,10 +842,7 @@ function Prometheus:metric_data()
         end
         seen_metrics[short_name] = true
       end
-      -- Replace "Inf" with "+Inf" in each metric's last bucket 'le' label.
-      if key:find('le="Inf"', 1, true) then
-        key = key:gsub('le="Inf"', 'le="+Inf"')
-      end
+      key = format_bucket_when_expose(key)
       table.insert(output, string.format("%s%s %s\n", self.prefix, key, value))
     else
       if type(err) == "string" then

prometheus_test.lua

@@ -574,7 +574,8 @@ function TestPrometheus:testCustomBucketer2()
   luaunit.assertEquals(ngx.logs, nil)
 end
 function TestPrometheus:testCollect()
-  local hist3 = self.p:histogram("b1", "Bytes", {"var"}, {100, 2000})
+  local hist3 = self.p:histogram("b1", "Bytes", {"var", "stale"}, {0.1, 100, 2000})
+  local hist4 = self.p:histogram("b2", "Labels", {}, {100, 2000})
   self.counter1:inc(5)
   self.counter2:inc(2, {"v2", "v1"})
   self.counter2:inc(2, {"v2", "v1"})
@@ -586,10 +587,15 @@ function TestPrometheus:testCollect()
   self.hist2:observe(3, {"ok", "site2"})
   self.hist2:observe(7, {"ok", "site2"})
   self.hist2:observe(70000, {"ok","site2"})
-  hist3:observe(50, {"ok"})
-  hist3:observe(50, {"ok"})
-  hist3:observe(150, {"ok"})
-  hist3:observe(5000, {"ok"})
+  hist3:observe(0.01, {"ok", "true"})
+  hist3:observe(50, {"ok", "true"})
+  hist3:observe(50, {"ok", "true"})
+  hist3:observe(150, {"ok", "true"})
+  hist3:observe(5000, {"ok", "true"})
+  hist4:observe(50, {})
+  hist4:observe(50, {})
+  hist4:observe(150, {})
+  hist4:observe(5000, {})
   self.p:collect()
 
   assert(find_idx(ngx.printed, "# HELP metric1 Metric 1") ~= nil)
@@ -607,10 +613,13 @@ function TestPrometheus:testCollect()
 
   assert(find_idx(ngx.printed, "# TYPE b1 histogram") ~= nil)
   assert(find_idx(ngx.printed, "# HELP b1 Bytes") ~= nil)
-  assert(find_idx(ngx.printed, 'b1_bucket{var="ok",le="0100.0"} 2') ~= nil)
-  assert(find_idx(ngx.printed, 'b1_sum{var="ok"} 5250') ~= nil)
+  assert(find_idx(ngx.printed, 'b1_bucket{var="ok",stale="true",le="0.1"} 1') ~= nil)
+  assert(find_idx(ngx.printed, 'b1_bucket{var="ok",stale="true",le="100"} 3') ~= nil)
+  assert(find_idx(ngx.printed, 'b1_sum{var="ok",stale="true"} 5250.01') ~= nil)
+  assert(find_idx(ngx.printed, 'b2_bucket{le="100"} 2') ~= nil)
+  assert(find_idx(ngx.printed, 'b2_sum{} 5250') ~= nil)
 
-  assert(find_idx(ngx.printed, 'l2_bucket{var="ok",site="site2",le="04.000"} 2') ~= nil)
+  assert(find_idx(ngx.printed, 'l2_bucket{var="ok",site="site2",le="4"} 2') ~= nil)
   assert(find_idx(ngx.printed, 'l2_bucket{var="ok",site="site2",le="+Inf"} 4') ~= nil)
 
   -- check that type comment exists and is before any samples for the metric.
@@ -647,7 +656,7 @@ function TestPrometheus:testCollectWithPrefix()
 
   assert(find_idx(ngx.printed, "# TYPE test_pref_b1 histogram") ~= nil)
   assert(find_idx(ngx.printed, "# HELP test_pref_b1 Bytes") ~= nil)
-  assert(find_idx(ngx.printed, 'test_pref_b1_bucket{var="ok",le="0100.0"} 2') ~= nil)
+  assert(find_idx(ngx.printed, 'test_pref_b1_bucket{var="ok",le="100"} 2') ~= nil)
   assert(find_idx(ngx.printed, 'test_pref_b1_sum{var="ok"} 5250') ~= nil)
 end