Console exporter display exponential histogram buckets #4344

alanwest · 2023-03-29T19:35:32Z

Uses same format as the collector. For sake of comparison, I've included the output from our exporter and the collector's exporter using the following code.

Code

var histogram = meter.CreateHistogram<double>("histogram");
histogram.Record(-1000.01);
histogram.Record(-1000);
histogram.Record(0);
histogram.Record(1000);
histogram.Record(1000.01);

.NET console exporter

Export histogram, Meter: TestMeter
(2023-03-29T19:21:36.9011200Z, 2023-03-29T19:21:36.9130980Z] ExponentialHistogram
Value: Sum: 0 Count: 5 Min: -1000.01 Max: 1000.01 
Bucket [-1000.009769, -1000.010430), Count: 1
Bucket [-1000.009108, -1000.009769), Count: 0
Bucket [-1000.008447, -1000.009108), Count: 0
Bucket [-1000.007786, -1000.008447), Count: 0
Bucket [-1000.007125, -1000.007786), Count: 0
Bucket [-1000.006464, -1000.007125), Count: 0
Bucket [-1000.005803, -1000.006464), Count: 0
Bucket [-1000.005142, -1000.005803), Count: 0
Bucket [-1000.004480, -1000.005142), Count: 0
Bucket [-1000.003819, -1000.004480), Count: 0
Bucket [-1000.003158, -1000.003819), Count: 0
Bucket [-1000.002497, -1000.003158), Count: 0
Bucket [-1000.001836, -1000.002497), Count: 0
Bucket [-1000.001175, -1000.001836), Count: 0
Bucket [-1000.000514, -1000.001175), Count: 0
Bucket [-999.999853, -1000.000514), Count: 1
Bucket [0, 0], Count: 1
Bucket (999.999853, 1000.000514], Count: 1
Bucket (1000.000514, 1000.001175], Count: 0
Bucket (1000.001175, 1000.001836], Count: 0
Bucket (1000.001836, 1000.002497], Count: 0
Bucket (1000.002497, 1000.003158], Count: 0
Bucket (1000.003158, 1000.003819], Count: 0
Bucket (1000.003819, 1000.004480], Count: 0
Bucket (1000.004480, 1000.005142], Count: 0
Bucket (1000.005142, 1000.005803], Count: 0
Bucket (1000.005803, 1000.006464], Count: 0
Bucket (1000.006464, 1000.007125], Count: 0
Bucket (1000.007125, 1000.007786], Count: 0
Bucket (1000.007786, 1000.008447], Count: 0
Bucket (1000.008447, 1000.009108], Count: 0
Bucket (1000.009108, 1000.009769], Count: 0
Bucket (1000.009769, 1000.010430], Count: 1

Collector logging exporter

2023-03-29T19:24:40.614Z	info	ResourceMetrics #0
Resource SchemaURL: 
Resource attributes:
     -> service.name: Str(myservice)
     -> service.instance.id: Str(7a1a598d-ed31-410d-ae57-864a652e3433)
ScopeMetrics #0
ScopeMetrics SchemaURL: 
InstrumentationScope TestMeter 
Metric #0
Descriptor:
     -> Name: histogram
     -> Description: 
     -> Unit: 
     -> DataType: ExponentialHistogram
     -> AggregationTemporality: Cumulative
ExponentialHistogramDataPoints #0
StartTimestamp: 2023-03-29 19:24:40.525425 +0000 UTC
Timestamp: 2023-03-29 19:24:40.612426 +0000 UTC
Count: 5
Sum: 0.000000
Min: -1000.010000
Max: 1000.010000
Bucket (-1000.010430, -1000.009769], Count: 1
Bucket (-1000.009769, -1000.009108], Count: 0
Bucket (-1000.009108, -1000.008447], Count: 0
Bucket (-1000.008447, -1000.007786], Count: 0
Bucket (-1000.007786, -1000.007125], Count: 0
Bucket (-1000.007125, -1000.006464], Count: 0
Bucket (-1000.006464, -1000.005803], Count: 0
Bucket (-1000.005803, -1000.005142], Count: 0
Bucket (-1000.005142, -1000.004480], Count: 0
Bucket (-1000.004480, -1000.003819], Count: 0
Bucket (-1000.003819, -1000.003158], Count: 0
Bucket (-1000.003158, -1000.002497], Count: 0
Bucket (-1000.002497, -1000.001836], Count: 0
Bucket (-1000.001836, -1000.001175], Count: 0
Bucket (-1000.001175, -1000.000514], Count: 0
Bucket (-1000.000514, -999.999853], Count: 1
Bucket [0, 0], Count: 1
Bucket [999.999853, 1000.000514), Count: 1
Bucket [1000.000514, 1000.001175), Count: 0
Bucket [1000.001175, 1000.001836), Count: 0
Bucket [1000.001836, 1000.002497), Count: 0
Bucket [1000.002497, 1000.003158), Count: 0
Bucket [1000.003158, 1000.003819), Count: 0
Bucket [1000.003819, 1000.004480), Count: 0
Bucket [1000.004480, 1000.005142), Count: 0
Bucket [1000.005142, 1000.005803), Count: 0
Bucket [1000.005803, 1000.006464), Count: 0
Bucket [1000.006464, 1000.007125), Count: 0
Bucket [1000.007125, 1000.007786), Count: 0
Bucket [1000.007786, 1000.008447), Count: 0
Bucket [1000.008447, 1000.009108), Count: 0
Bucket [1000.009108, 1000.009769), Count: 0
Bucket [1000.009769, 1000.010430), Count: 1

codecov · 2023-03-29T19:51:27Z

Codecov Report

Merging #4344 (7508b9c) into main (533513f) will decrease coverage by 0.07%.
The diff coverage is 0.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4344      +/-   ##
==========================================
- Coverage   84.66%   84.59%   -0.07%     
==========================================
  Files         298      298              
  Lines       11971    11990      +19     
==========================================
+ Hits        10135    10143       +8     
- Misses       1836     1847      +11

Impacted Files	Coverage Δ
...elemetry.Exporter.Console/ConsoleMetricExporter.cs	`0.00% <0.00%> (ø)`

... and 1 file with indirect coverage changes

reyang · 2023-03-29T20:45:46Z

src/OpenTelemetry.Exporter.Console/ConsoleMetricExporter.cs

+                                    negativeBucketCounts = new List<string>();
+                                }
+
+                                var lowerBound = Math.Exp(offset * factor).ToString("F6", CultureInfo.InvariantCulture);


Curious, where is this F6 coming from, does it provide a good precision (rather than having two different buckets printed out the same thing)?

reyang · 2023-03-29T20:47:03Z

src/OpenTelemetry.Exporter.Console/ConsoleMetricExporter.cs

+
+                            if (exponentialHistogramData.ZeroCount != 0)
+                            {
+                                bucketsBuilder.AppendLine($"Bucket [0, 0], Count: {exponentialHistogramData.ZeroCount}");


I guess ZeroCount is for [0, IEEE754 epsilon / 2].

opentelemetry-dotnet/test/OpenTelemetry.Tests/Metrics/Base2ExponentialBucketHistogramTest.cs

Line 145 in 63de729

Assert.Equal(-1075, histogram.MapToIndex(IEEE754Double.FromString("0 00000000000 0000000000000000000000000000000000000000000000000001"))); // ~4.9406564584124654E-324 (minimum subnormal positive, double.Epsilon, 2 ^ -1074)

From a learning perspective, I think the output helps folk derive an intuition for exponential histograms. I'm not opposed to getting more technical and surfacing up details of the underlying IEEE 754 representation of things, but I wonder if it's helpful.

I think it'll be really bad if we have the wrong math here.
I suggest that either we use the right math, or don't use math (e.g. instead of saying [0, 0], use English - zero bucket)

https://github.com/open-telemetry/opentelemetry-proto/blob/7aa439cb0ba78afbd009d83f32fdda6c128e0342/opentelemetry/proto/metrics/v1/metrics.proto#L515-L519

English works for me.

reyang · 2023-03-29T20:50:14Z

src/OpenTelemetry.Exporter.Console/ConsoleMetricExporter.cs

+                                }
+
+                                var lowerBound = Math.Exp(offset * factor).ToString("F6", CultureInfo.InvariantCulture);
+                                var upperBound = Math.Exp(++offset * factor).ToString("F6", CultureInfo.InvariantCulture);


Is this going to give the accurate IEEE 754 representation or there will be drifts due to precision losses or we don't know?

I'm pretty confident this is absolutely imprecise 😆. I guess we need to consider the audience and use case we're trying to serve.

To me this verbose format is mainly for learning, debugging, non-production kind of use cases.

F6 truncates things to 6 decimal places so that the width of the output is somewhat fixed and easier to read. I chose 6 simply because that's what the collector seems to display (might just be default formatting in Go).

I essentially implemented the LowerBoundary reverse mapping method here

https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/metrics/data-model.md#all-scales-use-the-logarithm-function.

My understanding is that this is valid for both positive and negative scales. There is a note about the possibility that the maximum index is incorrectly computed as +Inf. I can verify.

utpilla · 2023-03-29T20:51:04Z

Is this discrepancy in the outputs expected?

ConsoleExporter

Bucket [-1000.009769, -1000.010430), Count: 1
Bucket [-999.999853, -1000.000514), Count: 1

Collector

Bucket (-1000.010430, -1000.009769], Count: 1
Bucket (-1000.000514, -999.999853], Count: 1

alanwest · 2023-03-29T22:01:25Z

Is this discrepancy in the outputs expected?

Good eye. Had the bounds reversed. Fixed. You might have also noticed the difference in the interval notation. This is a bug in the collector. I fixed it yesterday open-telemetry/opentelemetry-collector#7445

github-actions · 2023-04-06T03:16:47Z

This PR was marked stale due to lack of activity and will be closed in 7 days. Commenting or Pushing will instruct the bot to automatically remove the label. This bot runs once per day.

github-actions · 2023-04-14T03:16:46Z

Closed as inactive. Feel free to reopen if this PR is still being worked on.

Console exporter display exponential histogram buckets

6ca4530

alanwest requested a review from a team March 29, 2023 19:35

reyang reviewed Mar 29, 2023

View reviewed changes

Fix display of negative bucket bounds

d2f76b4

alanwest added 3 commits March 29, 2023 15:03

Fix display of negative bucket bounds

e044367

Speak English

6fb5a7d

Merge branch 'main' into alanwest/console-exporter-buckets

7508b9c

github-actions bot added the Stale Issues and pull requests which have been flagged for closing due to inactivity label Apr 6, 2023

github-actions bot closed this Apr 14, 2023

alanwest mentioned this pull request Apr 26, 2023

Support Exponential Histogram #4189

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alanwest mentioned this pull request May 18, 2023

Console exporter: Display exponential histogram boundaries #4507

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Console exporter display exponential histogram buckets #4344

Console exporter display exponential histogram buckets #4344

alanwest commented Mar 29, 2023

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Console exporter display exponential histogram buckets #4344

Console exporter display exponential histogram buckets #4344

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alanwest commented Mar 29, 2023

Code

.NET console exporter

Collector logging exporter

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utpilla commented Mar 29, 2023

ConsoleExporter

Collector

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