Rename "Weights" to "Counts", cleanup the doc.

src/metrics/prometheus_histogram.erl

@@ -31,10 +31,11 @@
 %% </pre>
 %%
 %% The `prometheus_histogram:observe_n/3,4,5' adds limited support for the
-%% weighted histograms. It accepts the extra argument "Weight" which is limited
-%% to integer numbers to fit existing bucket counters data type. It may be, for
-%% example, the number of time ticks when the recent value was observed,
-%% allowing for better accuracy when measurements are irregular.
+%% "weighted" histograms. It accepts the extra integer argument "Count" to
+%% update the number of observations in the bucket by adding that number.
+%% This allows for better accuracy in the case of irregular measurements,
+%% assuming that the "Count" conveys the observation time interval (for
+%% example, the number of time ticks when the recent value was observed).
 %%
 %% @end
 
@@ -205,46 +206,46 @@ observe(Registry, Name, LabelValues, Value) when is_number(Value) ->
 observe(_Registry, _Name, _LabelValues, Value) ->
   erlang:error({invalid_value, Value, "observe accepts only numbers"}).
 
-%% @equiv observe_n(default, Name, [], Value, Weight)
-observe_n(Name, Value, Weight) ->
-  observe_n(default, Name, [], Value, Weight).
+%% @equiv observe_n(default, Name, [], Value, Count)
+observe_n(Name, Value, Count) ->
+  observe_n(default, Name, [], Value, Count).
 
-%% @equiv observe_n(default, Name, LabelValues, Value, Weight)
-observe_n(Name, LabelValues, Value, Weight) ->
-  observe_n(default, Name, LabelValues, Value, Weight).
+%% @equiv observe_n(default, Name, LabelValues, Value, Count)
+observe_n(Name, LabelValues, Value, Count) ->
+  observe_n(default, Name, LabelValues, Value, Count).
 
-%% @doc Observes the given `Value' with weight `Weight'.
+%% @doc Observes the given `Value' `Count' times.
 %%
 %% Raises `{invalid_value, Value, Message}' if `Value' isn't a number.<br/>
-%% Raises `{invalid_weight, Weight, Message}' if `Weight' isn't integer.<br/>
+%% Raises `{invalid_count, Count, Message}' if `Count' isn't integer.<br/>
 %% Raises `{unknown_metric, Registry, Name}' error if histogram with named
 %% `Name' can't be found in `Registry'.<br/>
 %% Raises `{invalid_metric_arity, Present, Expected}' error if labels count
 %% mismatch.
 %% @end
-observe_n(Registry, Name, LabelValues, Value, Weight) when is_integer(Value), is_integer(Weight) ->
+observe_n(Registry, Name, LabelValues, Value, Count) when is_integer(Value), is_integer(Count) ->
   Key = key(Registry, Name, LabelValues),
   case ets:lookup(?TABLE, Key) of
     [Metric] ->
       BucketPosition = calculate_histogram_bucket_position(Metric, Value),
       ets:update_counter(?TABLE, Key,
-                         [{?ISUM_POS, Value * Weight},
-                          {?BUCKETS_START + BucketPosition, Weight}]);
+                         [{?ISUM_POS, Value * Count},
+                          {?BUCKETS_START + BucketPosition, Count}]);
     [] ->
-      insert_metric(Registry, Name, LabelValues, Value, Weight, fun observe_n/5)
+      insert_metric(Registry, Name, LabelValues, Value, Count, fun observe_n/5)
   end,
   ok;
-observe_n(Registry, Name, LabelValues, Value, Weight) when is_number(Value), is_integer(Weight) ->
+observe_n(Registry, Name, LabelValues, Value, Count) when is_number(Value), is_integer(Count) ->
   Key = key(Registry, Name, LabelValues),
   case ets:lookup(?TABLE, Key) of
     [Metric] ->
-      fobserve_impl(Key, Metric, Value, Weight);
+      fobserve_impl(Key, Metric, Value, Count);
     [] ->
-      insert_metric(Registry, Name, LabelValues, Value, Weight, fun observe_n/5)
+      insert_metric(Registry, Name, LabelValues, Value, Count, fun observe_n/5)
   end;
-observe_n(_Registry, _Name, _LabelValues, Value, Weight) when is_number(Value) ->
-  erlang:error({invalid_weight, Weight, "observe_n accepts only integer weights"});
-observe_n(_Registry, _Name, _LabelValues, Value, _Weight) ->
+observe_n(_Registry, _Name, _LabelValues, Value, Count) when is_number(Value) ->
+  erlang:error({invalid_count, Count, "observe_n accepts only integer counts"});
+observe_n(_Registry, _Name, _LabelValues, Value, _Count) ->
   erlang:error({invalid_value, Value, "observe_n accepts only number values"}).
 
 %% @private
@@ -461,17 +462,17 @@ insert_metric(Registry, Name, LabelValues, Value, CB) ->
   insert_placeholders(Registry, Name, LabelValues),
   CB(Registry, Name, LabelValues, Value).
 
-insert_metric(Registry, Name, LabelValues, Value, Weight, CB) ->
+insert_metric(Registry, Name, LabelValues, Value, Count, CB) ->
   insert_placeholders(Registry, Name, LabelValues),
-  CB(Registry, Name, LabelValues, Value, Weight).
+  CB(Registry, Name, LabelValues, Value, Count).
 
-fobserve_impl(Key, Metric, Value, Weight) ->
+fobserve_impl(Key, Metric, Value, Count) ->
   Buckets = metric_buckets(Metric),
   BucketPos = calculate_histogram_bucket_position(Metric, Value),
-  fobserve_impl(Key, Buckets, BucketPos, Value, Weight).
+  fobserve_impl(Key, Buckets, BucketPos, Value, Count).
 
-fobserve_impl(Key, Buckets, BucketPos, Value, Weight) ->
-  ets:select_replace(?TABLE, generate_select_replace(Key, Buckets, BucketPos, Value, Weight)).
+fobserve_impl(Key, Buckets, BucketPos, Value, Count) ->
+  ets:select_replace(?TABLE, generate_select_replace(Key, Buckets, BucketPos, Value, Count)).
 
 insert_placeholders(Registry, Name, LabelValues) ->
   MF = prometheus_metric:check_mf_exists(?TABLE, Registry, Name, LabelValues),
@@ -490,13 +491,13 @@ calculate_histogram_bucket_position(Metric, Value) ->
   Buckets = metric_buckets(Metric),
   prometheus_buckets:position(Buckets, Value).
 
-generate_select_replace(Key, Bounds, BucketPos, Value, Weight) ->
+generate_select_replace(Key, Bounds, BucketPos, Value, Count) ->
   BoundPlaceholders = gen_query_bound_placeholders(Bounds),
   HistMatch = list_to_tuple([Key, '$2', '$3', '$4'] ++ BoundPlaceholders),
   BucketUpdate = lists:sublist(BoundPlaceholders, BucketPos)
-    ++ [{'+', gen_query_placeholder(?BUCKETS_START + BucketPos), Weight}]
+    ++ [{'+', gen_query_placeholder(?BUCKETS_START + BucketPos), Count}]
     ++ lists:nthtail(BucketPos + 1, BoundPlaceholders),
-  HistUpdate = list_to_tuple([{Key}, '$2', '$3', {'+', '$4', Value * Weight}] ++ BucketUpdate),
+  HistUpdate = list_to_tuple([{Key}, '$2', '$3', {'+', '$4', Value * Count}] ++ BucketUpdate),
   [{HistMatch,
     [],
     [{HistUpdate}]}].

test/eunit/metric/prometheus_histogram_tests.erl

@@ -107,7 +107,7 @@ test_errors(_) ->
                  prometheus_histogram:observe(request_duration, "qwe")),
    ?_assertError({invalid_value, "qwe", "observe_n accepts only number values"},
                  prometheus_histogram:observe_n(request_duration, "qwe", 3)),
-   ?_assertError({invalid_weight, "qwe", "observe_n accepts only integer weights"},
+   ?_assertError({invalid_count, "qwe", "observe_n accepts only integer counts"},
                  prometheus_histogram:observe_n(request_duration, 300, "qwe")),
    ?_assertError({invalid_value, "qwe", "observe_duration accepts only functions"},
                  prometheus_histogram:observe_duration(pool_size, "qwe"))