Document and test histogram's pobserve/6 function

prometheus-erl · Mar 9, 2025 · 36387e6 · 36387e6
1 parent af3adeb
commit 36387e6
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diff --git a/src/metrics/prometheus_histogram.erl b/src/metrics/prometheus_histogram.erl
@@ -268,7 +268,12 @@ observe_n(_Registry, _Name, _LabelValues, Value, Count) when is_number(Value) ->
 observe_n(_Registry, _Name, _LabelValues, Value, _Count) ->
     erlang:error({invalid_value, Value, "observe_n accepts only number values"}).
 
-?DOC(false).
+?DOC("""
+Observes the given `Value`, `Count` times, in the bucket position of the bucket list.
+
+Useful when the bucket position is known in advance, as it avoids having to compute such value
+during the observation.
+""").
 -spec pobserve(Registry, Name, LabelValues, Buckets, BucketPos, Value) -> ok when
     Registry :: prometheus_registry:registry(),
     Name :: prometheus_metric:name(),
@@ -289,7 +294,7 @@ pobserve(Registry, Name, LabelValues, Buckets, BucketPos, Value) when is_integer
             insert_metric(Registry, Name, LabelValues, Value, Fun)
     end,
     ok;
-pobserve(Registry, Name, LabelValues, Buckets, BucketPos, Value) when is_number(Value) ->
+pobserve(Registry, Name, LabelValues, Buckets, BucketPos, Value) when is_float(Value) ->
     Key = key(Registry, Name, LabelValues),
     case fobserve_impl(Key, Buckets, BucketPos, Value, 1) of
         0 ->

diff --git a/test/eunit/metric/prometheus_histogram_tests.erl b/test/eunit/metric/prometheus_histogram_tests.erl
@@ -10,6 +10,7 @@ prometheus_format_test_() ->
         fun test_errors/1,
         fun test_buckets/1,
         fun test_observe/1,
+        fun test_pobserve/1,
         fun test_observe_n/0,
         fun test_observe_duration_seconds/1,
         fun test_observe_duration_milliseconds/1,
@@ -274,6 +275,43 @@ test_observe(_) ->
         ?_assertEqual({[0, 0, 0, 0, 0, 0], 0}, RValue)
     ].
 
+test_pobserve(_) ->
+    Name = http_request_duration_milliseconds,
+    Buckets = [100, 300, 500, 750, 1000, infinity],
+    prometheus_histogram:new([
+        {name, Name},
+        {labels, [method]},
+        {buckets, Buckets},
+        {help, "Http Request execution time"},
+        {duration_unit, false}
+    ]),
+    prometheus_histogram:pobserve(default, Name, [get], Buckets, 0, 95),
+    prometheus_histogram:pobserve(default, Name, [get], Buckets, 0, 100),
+    prometheus_histogram:pobserve(default, Name, [get], Buckets, 1, 102),
+    prometheus_histogram:pobserve(default, Name, [get], Buckets, 1, 150),
+    prometheus_histogram:pobserve(default, Name, [get], Buckets, 1, 250),
+    prometheus_histogram:pobserve(default, Name, [get], Buckets, 0, 75),
+    prometheus_histogram:pobserve(default, Name, [get], Buckets, 2, 350),
+    prometheus_histogram:pobserve(default, Name, [get], Buckets, 3, 550),
+    prometheus_histogram:pobserve(default, Name, [get], Buckets, 4, 950),
+    prometheus_histogram:pobserve(default, Name, [get], Buckets, 3, 500.2),
+    prometheus_histogram:pobserve(default, Name, [get], Buckets, 1, 150.4),
+    prometheus_histogram:pobserve(default, Name, [get], Buckets, 2, 450.5),
+    prometheus_histogram:pobserve(default, Name, [get], Buckets, 4, 850.3),
+    prometheus_histogram:pobserve(default, Name, [get], Buckets, 4, 750.9),
+    prometheus_histogram:pobserve(default, Name, [get], Buckets, 5, 1650.23),
+    Value = prometheus_histogram:value(Name, [get]),
+    prometheus_histogram:reset(Name, [get]),
+    RValue = prometheus_histogram:value(Name, [get]),
+    [
+        ?_assertMatch(
+            {[3, 4, 2, 2, 3, 1], Sum} when
+                Sum > 6974.5 andalso Sum < 6974.55,
+            Value
+        ),
+        ?_assertEqual({[0, 0, 0, 0, 0, 0], 0}, RValue)
+    ].
+
 test_observe_n() ->
     prometheus_histogram:new([{name, temp}, {help, "temp"}, {buckets, [10, 20, 30, 40, 50]}]),
     ?assertEqual({[0, 0, 0, 0, 0, 0], 0}, prometheus_histogram:value(temp)),