Prometheus quantile summaries

doc/operation-and-maintenance/MongooseIM-metrics.md

@@ -50,16 +50,17 @@ All metrics are divided into the following groups:
 
     <h3>`histogram`</h3>
 
-    A histogram collects values and groups them in buckets.
+    A histogram collects values and exposes the number of observations and their sum (as counters), along with the 50th, 75th, 90th, 95th, 99th, and 99.9th percentiles with 1% accuracy.
 
     **Example:**
         ```
-        # TYPE xmpp_element_in_byte_size histogram
+        # TYPE xmpp_element_in_byte_size summary
         # HELP xmpp_element_in_byte_size Event: xmpp_element_in, Metric: byte_size
-        xmpp_element_in_byte_size_bucket{connection_type="c2s",host_type="localhost",le="1"} 0
+        xmpp_element_in_byte_size_count{connection_type="c2s",host_type="localhost"} 0
+        xmpp_element_in_byte_size_sum{connection_type="c2s",host_type="localhost"} 0
+        xmpp_element_in_byte_size{connection_type="c2s",host_type="localhost",quantile="0.5"} 0
         ...
-        xmpp_element_in_byte_size_bucket{connection_type="c2s",host_type="localhost",le="1073741824"} 0
-        xmpp_element_in_byte_size_bucket{connection_type="c2s",host_type="localhost",le="+Inf"} 0
+        xmpp_element_in_byte_size{connection_type="c2s",host_type="localhost",quantile="0.999"} 0
         ```
 
 === "Exometer"

rebar.config

@@ -56,8 +56,8 @@
   {exometer_report_statsd, {git, "https://github.com/esl/exometer_report_statsd.git", {branch, "master"}}},
   {syslogger, "0.3.0"},
   {flatlog, "0.1.2"},
-  {prometheus, "5.0.0"},
-  {prometheus_cowboy, "0.1.9"},
+  {prometheus, "6.1.1"},
+  {prometheus_cowboy, "0.2.0"},
 
   %%% Stateless libraries
   {opuntia, "1.1.2"},

rebar.lock

@@ -1,5 +1,5 @@
 {"1.2.0",
-[{<<"accept">>,{pkg,<<"accept">>,<<"0.3.6">>},2},
+[{<<"accept">>,{pkg,<<"accept">>,<<"0.3.7">>},2},
  {<<"amqp_client">>,{pkg,<<"amqp_client">>,<<"4.2.1">>},0},
  {<<"backoff">>,{pkg,<<"backoff">>,<<"1.1.6">>},1},
  {<<"base16">>,{pkg,<<"base16">>,<<"2.0.1">>},1},
@@ -19,6 +19,7 @@
  {<<"credentials_obfuscation">>,
   {pkg,<<"credentials_obfuscation">>,<<"3.5.0">>},
   1},
+ {<<"ddskerl">>,{pkg,<<"ddskerl">>,<<"0.4.2">>},1},
  {<<"eini">>,{pkg,<<"eini">>,<<"1.2.9">>},1},
  {<<"eodbc">>,{pkg,<<"eodbc">>,<<"0.2.0">>},0},
  {<<"epgsql">>,{pkg,<<"epgsql">>,<<"4.7.1">>},0},
@@ -87,10 +88,9 @@
   0},
  {<<"parse_trans">>,{pkg,<<"parse_trans">>,<<"3.4.0">>},1},
  {<<"pooler">>,{pkg,<<"pooler">>,<<"1.5.3">>},1},
- {<<"prometheus">>,{pkg,<<"prometheus">>,<<"5.0.0">>},0},
- {<<"prometheus_cowboy">>,{pkg,<<"prometheus_cowboy">>,<<"0.1.9">>},0},
- {<<"prometheus_httpd">>,{pkg,<<"prometheus_httpd">>,<<"2.1.13">>},1},
- {<<"quantile_estimator">>,{pkg,<<"quantile_estimator">>,<<"1.0.2">>},1},
+ {<<"prometheus">>,{pkg,<<"prometheus">>,<<"6.1.1">>},0},
+ {<<"prometheus_cowboy">>,{pkg,<<"prometheus_cowboy">>,<<"0.2.0">>},0},
+ {<<"prometheus_httpd">>,{pkg,<<"prometheus_httpd">>,<<"2.1.15">>},1},
  {<<"quickrand">>,{pkg,<<"quickrand">>,<<"2.0.7">>},1},
  {<<"rabbit_common">>,{pkg,<<"rabbit_common">>,<<"4.2.1">>},1},
  {<<"ranch">>,{pkg,<<"ranch">>,<<"2.2.0">>},0},
@@ -118,7 +118,7 @@
  {<<"worker_pool">>,{pkg,<<"worker_pool">>,<<"6.4.0">>},0}]}.
 [
 {pkg_hash,[
- {<<"accept">>, <<"AD44AC7D704BF70EF8FB2E313EF5B978F9D1330BDDAC64509E93AFDA13281215">>},
+ {<<"accept">>, <<"CD6E34A2D7E28CA38B2D3CB233734CA0C221EFBC1F171F91FEC5F162CC2D18DA">>},
  {<<"amqp_client">>, <<"CFF0CC13186E57457DC5745F1B3A4127C6857717CB8F5920DC457C84D0AD00A2">>},
  {<<"backoff">>, <<"83B72ED2108BA1EE8F7D1C22E0B4A00CFE3593A67DBC792799E8CCE9F42F796B">>},
  {<<"base16">>, <<"F0549F732E03BE8124ED0D19FD5EE52146CC8BE24C48CBC3F23AB44B157F11A2">>},
@@ -132,6 +132,7 @@
  {<<"cowlib">>, <<"623791C56C1CC9DF54A71A9C55147A401549917F00A2E48A6AE12B812C586CED">>},
  {<<"cpool">>, <<"76222AA1DAC0F8089707167BD69D221EDA63DB65B8BD67DBF6E133075392EEDC">>},
  {<<"credentials_obfuscation">>, <<"61E282ADFB4439486B3994FAAEC69543C7EE6CC7E70C6340E8853FD9DEAF8219">>},
+ {<<"ddskerl">>, <<"A51A90BE9AC9B36A94017670BED479C623B10CA9D4BDA1EDF3A0E48CAEEADA2A">>},
  {<<"eini">>, <<"FCC3CBD49BBDD9A1D9735C7365DAFFCD84481CCE81E6CB80537883AA44AC4895">>},
  {<<"eodbc">>, <<"81AC713AE657FC4F67FEA210AE6D4575DDD7003C96953363908EA35E80F33F22">>},
  {<<"epgsql">>, <<"D4E47CAE46C18C8AFA88E34D59A9B4BAE16368D7CE1EB3DA24FA755EB28393EB">>},
@@ -164,10 +165,9 @@
  {<<"p1_utils">>, <<"67B0C4AC9FA3BA3EF563B31AA111B0A004439A37FAC85E027F1C3617E1C7EC6C">>},
  {<<"parse_trans">>, <<"BB87AC362A03CA674EBB7D9D498F45C03256ADED7214C9101F7035EF44B798C7">>},
  {<<"pooler">>, <<"898CD1FA301FC42D4A8ED598CE139B71CA85B54C16AB161152B5CC5FBDCFA1A8">>},
- {<<"prometheus">>, <<"8A37A3216D8DB019D19068602669C9819C099120F8E39994DD1BD3A3F5553376">>},
- {<<"prometheus_cowboy">>, <<"D9D5B300516A61ED5AE31391F8EEEEB202230081D32A1813F2D78772B6F274E1">>},
- {<<"prometheus_httpd">>, <<"F086390B4E4E3F41112889B745BAC53D26437B6139496E6700C2508858F5985B">>},
- {<<"quantile_estimator">>, <<"ECD281D40110FDD9BA62685531E4435E0839A52FD1058DA5564F1763E4642EF7">>},
+ {<<"prometheus">>, <<"3C9D8E2D4FCF948450550693F6A82FAE013D3665BA10AA55955B64C2875FADB3">>},
+ {<<"prometheus_cowboy">>, <<"526F75D9850A9125496F78BCEECCA0F237BC7B403C976D44508543AE5967DAD9">>},
+ {<<"prometheus_httpd">>, <<"8F767D819A5D36275EAB9264AFF40D87279151646776069BF69FBDBBD562BD75">>},
  {<<"quickrand">>, <<"D2BD76676A446E6A058D678444B7FDA1387B813710D1AF6D6E29BB92186C8820">>},
  {<<"rabbit_common">>, <<"1D64E391E12116B76B1425EB96B7552DE51F0301093EBA669B5334F4759CC1E8">>},
  {<<"ranch">>, <<"25528F82BC8D7C6152C57666CA99EC716510FE0925CB188172F41CE93117B1B0">>},
@@ -186,7 +186,7 @@
  {<<"uuid">>, <<"B2078D2CC814F53AFA52D36C91E08962C7E7373585C623F4C0EA6DFB04B2AF94">>},
  {<<"worker_pool">>, <<"0347B805A8E5804B5676A9885FB3B9B6C1627099C449C3C67C0E8E6AF79E9AA6">>}]},
 {pkg_hash_ext,[
- {<<"accept">>, <<"A5167FA1AE90315C3F1DD189446312F8A55D00EFA357E9C569BDA47736B874C3">>},
+ {<<"accept">>, <<"CA69388943F5DAD2E7232A5478F16086E3C872F48E32B88B378E1885A59F5649">>},
  {<<"amqp_client">>, <<"8AE00B055A58500E0557F73D9C0FFE257487131E603F7F84FE72CBFAAF03838A">>},
  {<<"backoff">>, <<"CF0CFFF8995FB20562F822E5CC47D8CCF664C5ECDC26A684CBE85C225F9D7C39">>},
  {<<"base16">>, <<"06EA2D48343282E712160BA89F692B471DB8B36ABE8394F3445FF9032251D772">>},
@@ -200,6 +200,7 @@
  {<<"cowlib">>, <<"0AF652D1550C8411C3B58EED7A035A7FB088C0B86AFF6BC504B0BC3B7F791AA2">>},
  {<<"cpool">>, <<"430E18DF4A9D584EB1ED0D196A87CC02E878AF5B4888BFDC9B65F86A96480E30">>},
  {<<"credentials_obfuscation">>, <<"843ADBE3246861CE0F1A0FA3222F384834EB31DEFD8D6B9CBA7AFD2977C957BC">>},
+ {<<"ddskerl">>, <<"63F907373D7E548151D584D4DA8A38928FD26EC9477B94C0FFAAD87D7CB69FE7">>},
  {<<"eini">>, <<"DA64AE8DB7C2F502E6F20CDF44CD3D9BE364412B87FF49FEBF282540F673DFCB">>},
  {<<"eodbc">>, <<"ACF72A61349AFD535306F036B8A17C45FA095E039F7C0211E671CCCBD709A8C8">>},
  {<<"epgsql">>, <<"B6D86B7DC42C8555B1D4E20880E5099D6D6D053148000E188E548F98E4E01836">>},
@@ -232,10 +233,9 @@
  {<<"p1_utils">>, <<"D0379E8C1156B98BD64F8129C1DE022FCCA4F2FDB7486CE73BF0ED2C3376B04C">>},
  {<<"parse_trans">>, <<"F99E368830BEA44552224E37E04943A54874F08B8590485DE8D13832B63A2DC3">>},
  {<<"pooler">>, <<"058D85C5081289B90E97E4DDDBC3BB5A3B4A19A728AB3BC88C689EFCC36A07C7">>},
- {<<"prometheus">>, <<"80D29564A5DC4490B53FD225D752B65FB0DBEBA41497F96D62223338127C5659">>},
- {<<"prometheus_cowboy">>, <<"5F71C039DEB9E9FF9DD6366BC74C907A463872B85286E619EFF0BDA15111695A">>},
- {<<"prometheus_httpd">>, <<"9B5A44D1F6FBB3C3FE6F85F06DAFE680AD9FFD591EC65A10BB51DFF0FBBE45D2">>},
- {<<"quantile_estimator">>, <<"DB404793D6384995A1AC6DD973E2CEE5BE9FCC128765BDBA53D87C564E296B64">>},
+ {<<"prometheus">>, <<"C3ECC7A35676948089E28FF4383CCB85DCEF447F0982C01E5630A084008C456A">>},
+ {<<"prometheus_cowboy">>, <<"2C7EB12F4B970D91E3B47BAAD0F138F6ADC34E53EEB0AE18068FF0AFAB441B24">>},
+ {<<"prometheus_httpd">>, <<"67736D000745184D5013C58A63E947821AB90CB9320BC2E6AE5D3061C6FFE039">>},
  {<<"quickrand">>, <<"B8ACBF89A224BC217C3070CA8BEBC6EB236DBE7F9767993B274084EA044D35F0">>},
  {<<"rabbit_common">>, <<"FF509B07E639B1784898C28031E5204FEA14260172E4FC339F94405586037E40">>},
  {<<"ranch">>, <<"FA0B99A1780C80218A4197A59EA8D3BDAE32FBFF7E88527D7D8A4787EFF4F8E7">>},

src/instrument/mongoose_instrument_exometer.erl

@@ -153,7 +153,7 @@ handle_metric_event(EventName, Labels, MetricName, MetricType, Measurements) ->
             ok
     end.
 
--spec update_metric(exometer:name(), spiral | histogram, integer()) -> ok.
+-spec update_metric(exometer:name(), mongoose_instrument:metric_type(), integer()) -> ok.
 update_metric(Name, gauge, Value) when is_integer(Value) ->
     ok = exometer:update(Name, Value);
 update_metric(Name, counter, Value) when is_integer(Value) ->

src/instrument/mongoose_instrument_prometheus.erl

@@ -57,7 +57,13 @@ declare_metric(MetricSpec, counter) ->
 declare_metric(MetricSpec, spiral) ->
     prometheus_counter:declare(MetricSpec);
 declare_metric(MetricSpec, histogram) ->
-    prometheus_histogram:declare([{buckets, histogram_buckets()} | MetricSpec]).
+    prometheus_quantile_summary:declare([
+        {quantiles, [0.5, 0.75, 0.90, 0.95, 0.99, 0.999]},
+        {error, 0.01},
+        %% Measuring in µs suffices for actions lasting up to a day (with 1% accuracy).
+        %% Measuring in bytes suffices for sizes up to 81 GB (with 1% accuracy).
+        {bound, 1260}
+    | MetricSpec]).
 
 -spec reset_metric(name(), [mongoose_instrument:label_value()],
                    mongoose_instrument:metric_type()) -> boolean().
@@ -68,7 +74,7 @@ reset_metric(Name, LabelValues, counter) ->
 reset_metric(Name, LabelValues, spiral) ->
     prometheus_counter:remove(Name, LabelValues);
 reset_metric(Name, LabelValues, histogram) ->
-    prometheus_histogram:remove(Name, LabelValues).
+    prometheus_quantile_summary:remove(Name, LabelValues).
 
 -spec initialize_metric(name(), [mongoose_instrument:label_value()],
                         mongoose_instrument:metric_type()) -> ok.
@@ -92,15 +98,6 @@ metric_spec(EventName, LabelKeys, MetricName) ->
      {duration_unit, false} % prevent unwanted implicit conversions, e.g. seconds -> microseconds
     ].
 
--spec histogram_buckets() -> [integer()].
-histogram_buckets() ->
-    histogram_buckets([], 1 bsl 30). % ~1.07 * 10^9
-
-histogram_buckets(AccBuckets, Val) when Val > 0 ->
-    histogram_buckets([Val | AccBuckets], Val bsr 1);
-histogram_buckets(AccBuckets, _Val) ->
-    AccBuckets.
-
 -spec handle_metric_event(mongoose_instrument:event_name(), [mongoose_instrument:label_value()],
                           mongoose_instrument:metric_name(), mongoose_instrument:metric_type(),
                           mongoose_instrument:measurements()) -> ok.
@@ -139,4 +136,4 @@ update_metric(Name, Labels, counter, Value) when is_integer(Value) ->
 update_metric(Name, Labels, spiral, Value) when is_integer(Value), Value >= 0 ->
     ok = prometheus_counter:inc(Name, Labels, Value);
 update_metric(Name, Labels, histogram, Value) when is_integer(Value) ->
-    ok = prometheus_histogram:observe(Name, Labels, Value).
+    ok = prometheus_quantile_summary:observe(Name, Labels, Value).

test/mongoose_instrument_metrics_SUITE.erl

@@ -10,6 +10,24 @@
 -define(HOST_TYPE, <<"localhost">>).
 -define(HOST_TYPE2, <<"test type">>).
 
+-define(assertRelEqual(Expect, Actual, Tolerance),
+    (fun() -> 
+        __Exp = (Expect),
+        __Act = (Actual),
+        __Tol = (Tolerance),
+        case __Exp == 0 of
+            true -> ?assertEqual(__Exp, __Act);
+            false ->
+                __RelErr = abs(__Exp - __Act) / __Exp,
+                __Check = case __RelErr < __Tol of
+                    true -> ok;
+                    false -> {fail, [{expected, __Exp}, {actual, __Act}, 
+                                        {rel_error, __RelErr}, {tolerance, __Tol}]}
+                end,
+                ?assertEqual(ok, __Check)
+        end
+    end)()).
+
 -import(mongoose_instrument_exometer, [exometer_metric_name/3]).
 %% Setup and teardown
 
@@ -30,6 +48,7 @@ groups() ->
                                prometheus_counter_cannot_be_decreased,
                                prometheus_counter_is_updated_separately_for_different_labels,
                                prometheus_histogram_is_created_and_updated,
+                               prometheus_histogram_is_calculated_correctly,
                                prometheus_histogram_is_updated_separately_for_different_labels,
                                multiple_prometheus_metrics_are_updated]},
      {exometer, [parallel], [exometer_skips_non_metric_event,
@@ -184,13 +203,33 @@ prometheus_histogram_is_created_and_updated(Config) ->
     ok = mongoose_instrument:set_up(Event, ?LABELS, #{metrics => #{time => histogram}}),
 
     %% Prometheus histogram shows no value if there is no data
-    ?assertEqual(undefined, prometheus_histogram:value(Metric, [?HOST_TYPE])),
+    ?assertEqual(undefined, prometheus_quantile_summary:value(Metric, [?HOST_TYPE])),
     ok = mongoose_instrument:execute(Event, ?LABELS, #{time => 1}),
-    ?assertMatch({[1, 0|_], 1}, prometheus_histogram:value(Metric, [?HOST_TYPE])),
+    ?assertMatch({1, 1, _}, prometheus_quantile_summary:value(Metric, [?HOST_TYPE])),
     ok = mongoose_instrument:execute(Event, ?LABELS, #{time => 1}),
-    ?assertMatch({[2, 0|_], 2}, prometheus_histogram:value(Metric, [?HOST_TYPE])),
+    ?assertMatch({2, 2, _}, prometheus_quantile_summary:value(Metric, [?HOST_TYPE])),
     ok = mongoose_instrument:execute(Event, ?LABELS, #{time => 2}),
-    ?assertMatch({[2, 1|_], 4}, prometheus_histogram:value(Metric, [?HOST_TYPE])).
+    ?assertMatch({3, 4, _}, prometheus_quantile_summary:value(Metric, [?HOST_TYPE])).
+
+prometheus_histogram_is_calculated_correctly(Config) ->
+    Event = ?config(event, Config),
+    Metric = prom_name(Event, time),
+    ok = mongoose_instrument:set_up(Event, ?LABELS, #{metrics => #{time => histogram}}),
+
+    %% Prometheus histogram shows no value if there is no data
+    ?assertEqual(undefined, prometheus_quantile_summary:value(Metric, [?HOST_TYPE])),
+    Values = [1, 2, 2, 2, 2, 2, 2, 9, 9, 10],
+    lists:foreach(fun(V) -> ok = mongoose_instrument:execute(Event, ?LABELS, #{time => V}) end, Values),
+    Sum = lists:sum(Values),
+    Length = length(Values),
+    ?assertMatch({Length, Sum, _}, prometheus_quantile_summary:value(Metric, [?HOST_TYPE])),
+    %% Check some quantiles
+    {_, _, Quantiles} = prometheus_quantile_summary:value(Metric, [?HOST_TYPE]),
+    Tolerance = 0.01,
+    ?assertRelEqual(2, proplists:get_value(0.5, Quantiles), Tolerance),
+    ?assertRelEqual(9, proplists:get_value(0.9, Quantiles), Tolerance),
+    ?assertRelEqual(10, proplists:get_value(0.95, Quantiles), Tolerance),
+    ?assertRelEqual(10, proplists:get_value(0.99, Quantiles), Tolerance).
 
 prometheus_histogram_is_updated_separately_for_different_labels(Config) ->
     Event = ?config(event, Config),
@@ -199,8 +238,8 @@ prometheus_histogram_is_updated_separately_for_different_labels(Config) ->
     ok = mongoose_instrument:set_up(Event, ?LABELS2, #{metrics => #{time => histogram}}),
     ok = mongoose_instrument:execute(Event, ?LABELS, #{time => 1}),
     ok = mongoose_instrument:execute(Event, ?LABELS2, #{time => 2}),
-    ?assertMatch({[1, 0|_], 1}, prometheus_histogram:value(Metric, [?HOST_TYPE])),
-    ?assertMatch({[0, 1|_], 2}, prometheus_histogram:value(Metric, [?HOST_TYPE2])).
+    ?assertMatch({1, 1, _}, prometheus_quantile_summary:value(Metric, [?HOST_TYPE])),
+    ?assertMatch({1, 2, _}, prometheus_quantile_summary:value(Metric, [?HOST_TYPE2])).
 
 multiple_prometheus_metrics_are_updated(Config) ->
     Event = ?config(event, Config),
@@ -211,18 +250,18 @@ multiple_prometheus_metrics_are_updated(Config) ->
     %% Update both metrics
     ok = mongoose_instrument:execute(Event, ?LABELS, #{count => 1, time => 2}),
     ?assertEqual(1, prometheus_counter:value(Counter, [?HOST_TYPE])),
-    HistogramValue = prometheus_histogram:value(Histogram, [?HOST_TYPE]),
-    ?assertMatch({[0, 1|_], 2}, HistogramValue),
+    HistogramValue = prometheus_quantile_summary:value(Histogram, [?HOST_TYPE]),
+    ?assertMatch({1, 2, _}, HistogramValue),
 
     %% Update only one metric
     ok = mongoose_instrument:execute(Event, ?LABELS, #{count => 2}),
     ?assertEqual(3, prometheus_counter:value(Counter, [?HOST_TYPE])),
-    ?assertEqual(HistogramValue, prometheus_histogram:value(Histogram, [?HOST_TYPE])),
+    ?assertEqual(HistogramValue, prometheus_quantile_summary:value(Histogram, [?HOST_TYPE])),
 
     %% No update
     ok = mongoose_instrument:execute(Event, ?LABELS, #{something => irrelevant}),
     ?assertEqual(3, prometheus_counter:value(Counter, [?HOST_TYPE])),
-    ?assertEqual(HistogramValue, prometheus_histogram:value(Histogram, [?HOST_TYPE])).
+    ?assertEqual(HistogramValue, prometheus_quantile_summary:value(Histogram, [?HOST_TYPE])).
 
 exometer_skips_non_metric_event(Config) ->
     Event = ?config(event, Config),
@@ -386,7 +425,7 @@ prometheus_and_exometer_metrics_are_updated(Config) ->
     ?assertEqual({ok, [{count, 1}]}, exometer:get_value([?HOST_TYPE, Event, count], count)),
     ?assertEqual({ok, [{mean, 2}]}, exometer:get_value([?HOST_TYPE, Event, time], mean)),
     ?assertEqual(1, prometheus_counter:value(prom_name(Event, count), [?HOST_TYPE])),
-    ?assertMatch({[0, 1|_], 2}, prometheus_histogram:value(prom_name(Event, time), [?HOST_TYPE])).
+    ?assertMatch({1, 2, _}, prometheus_quantile_summary:value(prom_name(Event, time), [?HOST_TYPE])).
 
 %% Helpers
 

test/prometheus_endpoint_SUITE.erl

@@ -54,7 +54,7 @@ test_metrics(Event, Labels) ->
     check_counter(Event, requests, Labels, 1, Scraped), % 'spiral' is a Prometheus counter
     check_gauge(Event, sessions, Labels, 5, Scraped), % 'counter' is a Prometheus gauge
     check_gauge(Event, seconds, Labels, 10, Scraped),
-    check_histogram(Event, time, Labels, #{count => 1, sum => 2, bucket_num => 32}, Scraped).
+    check_histogram(Event, time, Labels, #{count => 1, sum => 2}, Scraped).
 
 %% Checks for the parsed metrics
 
@@ -71,38 +71,14 @@ check_gauge(Event, Metric, Labels, ExpValue, Scraped) ->
     ?assertEqual({Labels, ExpValue}, Value).
 
 check_histogram(Event, Metric, Labels, ExpValues, Scraped) ->
-    #{count := ExpCount, sum := ExpSum, bucket_num := ExpBucketNum} = ExpValues,
-    [Type, Help] = get_metric([Event, Metric], Scraped),
-    ?assertEqual({<<"TYPE">>, <<"histogram">>}, Type),
+    #{count := ExpCount, sum := ExpSum} = ExpValues,
+    [Type, Help | _] = get_metric([Event, Metric], Scraped),
+    ?assertEqual({<<"TYPE">>, <<"summary">>}, Type),
     ?assertEqual({<<"HELP">>, help(Event, Metric)}, Help),
     [Count] = get_metric([Event, Metric, count], Scraped),
     ?assertEqual({Labels, ExpCount}, Count),
     [Sum] = get_metric([Event, Metric, sum], Scraped),
-    ?assertEqual({Labels, ExpSum}, Sum),
-    Buckets = get_metric([Event, Metric, bucket], Scraped),
-    ?assertEqual(ExpBucketNum, length(Buckets)),
-    check_buckets(ExpCount, Labels, Buckets).
-
-%% Check that the histogram buckets have growing thresholds and counts,
-%% and that the last bucket has the expected total count (because they are cumulative).
-check_buckets(ExpCount, Labels, Buckets) ->
-    InitState = #{labels => Labels, last_count => 0, last_threshold => 0},
-    #{final_count := LastCount} = lists:foldl(fun check_bucket/2, InitState, Buckets),
-    ?assertEqual(ExpCount, LastCount).
-
-check_bucket({Labels, Count}, State) ->
-    #{labels := BaseLabels, last_count := LastCount, last_threshold := LastThreshold} = State,
-    {ThresholdBin, Labels1} = maps:take(le, Labels),
-    ?assertEqual(Labels1, BaseLabels),
-    ?assert(Count >= LastCount),
-    case ThresholdBin of
-        <<"+Inf">> ->
-            #{final_count => Count};
-        _ ->
-            Threshold = binary_to_integer(ThresholdBin),
-            ?assert(Threshold > LastThreshold),
-            State#{last_count => Count, last_threshold => Threshold}
-    end.
+    ?assertEqual({Labels, ExpSum}, Sum).
 
 help(Event, Metric) ->
     <<"Event: ", (atom_to_binary(Event))/binary, ", Metric: ", (atom_to_binary(Metric))/binary>>.