Classic histogram and summary as complex types

Ref: prometheus/OpenMetrics#283

Signed-off-by: György Krajcsovits <gyorgy.krajcsovits@grafana.com>

Author: krajorama

docs/specs/om/open_metrics_spec_2_0.md

@@ -86,9 +86,8 @@ ComplexValue MUST contain all information necessary to recreate a sample value f
 
 The following Metric Types MUST use ComplexValue for Metric Values:
 
-TODO: Below will switch to Histogram and Summary in the next PR. 
-* [Histogram](#histogram) MetricFamily Type with [Native Buckets](#native-buckets).
-* [GaugeHistogram](#gauge-histogram) MetricFamily Type with [Native Buckets](#native-buckets).
+* [Histogram](#histogram) MetricFamily Type.
+* [GaugeHistogram](#gauge-histogram) MetricFamily Type.
 
 Other Metric Types MUST use Numbers.
 
@@ -412,6 +411,7 @@ ABNF as per RFC 5234
 ```abnf
 exposition = metricset HASH SP eof [ LF ]
 
+
 metricset = *metricfamily
 
 metricfamily = *metric-descriptor *metric
@@ -498,7 +498,7 @@ normal-char = %x00-09 / %x0B-21 / %x23-5B / %x5D-D7FF / %xE000-10FFFF
 start-timestamp = %d115.116 "@" timestamp
 
 ; Complex values
-complex-value = nativehistogram
+complex-value = nativehistogram / classic-histogram / classic-summary
 
 nativehistogram = nh-count "," nh-sum "," nh-schema "," nh-zero-threshold "," nh-zero-count [ "," nh-negative-spans "," nh-negative-buckets ] [ "," nh-positive-spans "," nh-positive-buckets ]
 
@@ -532,6 +532,32 @@ non-negative-integer = ["+"] 1*"0" / ["+"] positive-integer
 ; Leading 0s explicitly okay.
 positive-integer = *"0" positive-digit *DIGIT
 positive-digit = "1" / "2" / "3" / "4" / "5" / "6" / "7" / "8" / "9"
+
+; count:12,sum:100.0,bucket:[0.1:3,05:12,+Inf:12]
+classic-histogram = ch-count "," ch-sum "," ch-bucket
+
+; count:x where x is a real number, not +-Inf or NaN
+ch-count = %d99.111.117.110.116 ":" non-negative-integer
+; sum:x where x is a real number or +-Inf or NaN
+ch-sum = %d115.117.109 ":" number
+; bucket:[...]
+ch-bucket = %d98.117.99.107.101.116 ":" "[" ch-le-counts "]"
+ch-le-counts = ch-pos-inf-bucket / (ch-neg-inf-bucket / ch-le-bucket) *("," ch-le-bucket) "," ch-pos-inf-bucket
+ch-pos-inf-bucket = "+" %d73.110.102 ":" non-negative-integer
+ch-neg-inf-bucket = "-" %d73.110.102 ":" non-negative-integer
+ch-le-bucket = realnumber ":" non-negative-integer
+
+; count:12.0,sum:100.0,quantile:[0.9:2.0,0.95:3.0,0.99:20.0]
+classic-summary = cs-count "," cs-sum "," cs-quantile
+
+; count:x where x is a real number, not +-Inf or NaN
+cs-count = %d99.111.117.110.116 ":" non-negative-integer
+; sum:x where x is a real number or +-Inf or NaN
+cs-sum = %d115.117.109 ":" number
+; quantile:[...]
+cs-quantile = %d113.117.97.110.116.105.108.101 ":" "[" cs-q-counts "]"
+cs-q-counts = cs-q-count *("," cs-q-count)
+cs-q-count = realnumber ":" non-negative-integer
 ```
 
 #### Overall Structure
@@ -549,13 +575,16 @@ Line endings MUST be signalled with line feed (\n) and MUST NOT contain carriage
 An example of a complete exposition:
 
 ```openmetrics
+# TYPE acme_http_server_request_seconds histogram
+# UNIT acme_http_server_request_seconds seconds
+# HELP acme_http_server_request_seconds Latency though all of ACME's HTTP request service.
+acme_http_router_request_seconds{path="/api/v1",method="GET"} {count:10,sum:100.0,bucket:[0.1:2,0.5:10,+Inf:10]}
+acme_http_router_request_seconds{path="/api/v2",method="GET"} {count:1,sum:10.0,bucket:[0.1:1,0.5:1,+Inf:1]}
 # TYPE acme_http_router_request_seconds summary
 # UNIT acme_http_router_request_seconds seconds
 # HELP acme_http_router_request_seconds Latency though all of ACME's HTTP request router.
-acme_http_router_request_seconds_sum{path="/api/v1",method="GET"} 9036.32 st@1605281325.0
-acme_http_router_request_seconds_count{path="/api/v1",method="GET"} 807283.0 st@1605281325.0
-acme_http_router_request_seconds_sum{path="/api/v2",method="POST"} 479.3 st@1605301325.0
-acme_http_router_request_seconds_count{path="/api/v2",method="POST"} 34.0 st@1605301325.0
+acme_http_router_request_seconds{path="/api/v1",method="GET"} {count:807283,sum:9036.32,quantile:[0.95:2,0.99:20]} st@1605281325.0
+acme_http_router_request_seconds{path="/api/v2",method="GET"} {count:34,sum:479.3,quantile:[0.95:2,0.99:2]} st@1605301325.0
 # TYPE go_goroutines gauge
 # HELP go_goroutines Number of goroutines that currently exist.
 go_goroutines 69
@@ -973,19 +1002,7 @@ An example of a Metric with no labels and a MetricPoint with Sum, Count, and Sta
 
 ```openmetrics-add-eof
 # TYPE foo histogram
-foo_bucket{le="0.0"} 0 st@1520430000.123
-foo_bucket{le="1e-05"} 0 st@1521430000.123
-foo_bucket{le="0.0001"} 5 st@1521430020.123
-foo_bucket{le="0.1"} 8 st@1520430321.123
-foo_bucket{le="1.0"} 10 st@1522430000.123
-foo_bucket{le="10.0"} 11 st@1520430123.123
-foo_bucket{le="100000.0"} 11 st@1521430010.123
-foo_bucket{le="1e+06"} 15 st@1520430301.123
-foo_bucket{le="1e+23"} 16 st@1521430001.123
-foo_bucket{le="1.1e+23"} 17 st@1522430220.123
-foo_bucket{le="+Inf"} 17 st@1520430000.123
-foo_count 17 st@1520430000.123
-foo_sum 324789.3 st@1520430000.123
+foo {count:17,sum:324789.3,bucket:[0.0:0,1e-05:0,0.0001:5,0.1:8,1.0:10,10.0:11,100000.0:11,1e+06:15,1e+23:16,1.1e+23:17,+Inf:17]} st@1520430000.123
 ```
 
 ##### Histogram with Native Buckets
@@ -1037,11 +1054,7 @@ The order ensures that implementations can easily skip the Classic Buckets if th
 # UNIT acme_http_request_seconds seconds
 # HELP acme_http_request_seconds Latency histogram of all of ACME's HTTP requests.
 acme_http_request_seconds{path="/api/v1",method="GET"} {count:2,sum:1.2e2,schema:0,zero_threshold:1e-4,zero_count:0,positive_spans:[1:2],positive_buckets:[1,1]}
-acme_http_request_seconds_count{path="/api/v1",method="GET"} 2
-acme_http_request_seconds_sum{path="/api/v1",method="GET"} 1.2e2
-acme_http_request_seconds_buckets{path="/api/v1",method="GET",le="0.5"} 1
-acme_http_request_seconds_buckets{path="/api/v1",method="GET",le="1"} 2
-acme_http_request_seconds_buckets{path="/api/v1",method="GET",le="+Inf"} 2
+acme_http_request_seconds{path="/api/v1",method="GET"} {count:2,sum:1.2e2,bucket:[0.5:1,1:2,+Inf:2]}
 ```
 
 ###### Exemplars
@@ -1054,14 +1067,8 @@ The "0.01" bucket has no Exemplar. The 0.1 bucket has an Exemplar with no Labels
 
 ```openmetrics-add-eof
 # TYPE foo histogram
-foo {count:10,sum:1.0,schema:0,zero_threshold:1e-4,zero_count:0,positive_spans:[0:2],positive_buckets:[5,5]} st@1520430000.123 # {trace_id="shaZ8oxi"} 0.67 1520879607.789 # {trace_id="ookahn0M"} 1.2 1520879608.589
-foo_bucket{le="0.01"} 0 st@1520430000.123
-foo_bucket{le="0.1"} 8 st@1520430000.123 # {} 0.054
-foo_bucket{le="1"} 11 st@1520430000.123 # {trace_id="KOO5S4vxi0o"} 0.67
-foo_bucket{le="10"} 17 st@1520430000.123 # {trace_id="oHg5SJYRHA0"} 9.8 1520879607.789
-foo_bucket{le="+Inf"} 17 st@1520430000.123
-foo_count 17 st@1520430000.123
-foo_sum 324789.3 st@1520430000.123
+foo {count:17,sum:324789.3,schema:0,zero_threshold:1e-4,zero_count:0,positive_spans:[0:2],positive_buckets:[5,12]} st@1520430000.123 # {trace_id="shaZ8oxi"} 0.67 1520879607.789 # {trace_id="ookahn0M"} 1.2 1520879608.589
+foo {count:17,sum:324789.3,bucket:[0.01:0,0.1:8,1.0:11,10.0:17,+Inf:17]} st@1520430000.123 # {} 0.054 1520879607.7 # {trace_id="KOO5S4vxi0o"} 0.67 1520879602.890 # {trace_id="oHg5SJYRHA0"} 9.8 1520879607.789
 ```
 
 ##### GaugeHistogram with Classic Buckets
@@ -1074,13 +1081,7 @@ An example of a Metric with no labels, and one MetricPoint value with no Exempla
 
 ```openmetrics-add-eof
 # TYPE foo gaugehistogram
-foo_bucket{le="0.01"} 20.0
-foo_bucket{le="0.1"} 25.0
-foo_bucket{le="1"} 34.0
-foo_bucket{le="10"} 34.0
-foo_bucket{le="+Inf"} 42.0
-foo_gcount 42.0
-foo_gsum 3289.3
+foo {count:42,sum:3289.3,bucket:[0.01:20,0.1:25,1:34,+Inf:42]}
 ```
 
 ##### GaugeHistogram with Native Buckets