Probabilistic sampler processor based on draft t-value/r-value encoding #24811

jmacd · 2023-08-02T23:34:38Z

Description:
Draft for open-telemetry/opentelemetry-specification#3602.
Previously #22058, see also open-telemetry/oteps#235

Reviewers: thank you for your patience. While this has was first started in May 2023 and has progressed slowly, it's finally ready and the Sampling SIG has converged on this design.

This PR adds two consistent sampler modes to the existing probabilistic sampler, "equalizing" and "proportional". The consistent sampling mechanism used here is based on 56 bits of randomness which is extracted from the tracestate or the TraceID. Because this is a tail sampler, there is no real benefit to synthesizing an r-value, therefore when rv: is not set in the tracestate, this implementation unconditionally uses the TraceID bits.

When open-telemetry/opentelemetry-proto#503 is included in the next release of OTLP and pdata is extended with the corresponding field, this processor will be updated to use the randomness bit before deciding what to do about TraceIDs that do not have it set. We imagine adding a configuration parameter to indicate how to treat this scenario, but since this is a tail processor, there is little we can do that would be consistent, so using the TraceID bits as they are is probably best, despite the missing confirmation of their randomness.

Note there is a question of how to treat spans that arrive with an empty tracestate, indicating what is likely to be 100% sampling but could potentially be otherwise. There are no OpenTelemetry specifications for what we should do in this situation, and we leave this decision open.

Link to tracking Issue:
open-telemetry/opentelemetry-specification#1413

Testing: Complete.

Documentation: Added new documentation.

to iterate.

…tor-contrib into jmacd/tvaluesampler

…n#3602

…and resampler

jmacd · 2023-08-03T23:23:44Z

Based on the feedback received in Sampling SIG today, I refactored the implementation to avoid the use of floating point numbers except when explicitly converting thresholds to probabilities and back to thresholds. I have also added a second implementation of the based on byte arrays instead of unsigned numbers, for comparison. The unsigned implementation is trickier to read and write, but faster.

goos: darwin
goarch: arm64
pkg: github.com/open-telemetry/opentelemetry-collector-contrib/pkg/sampling
BenchmarkThresholdCompareAsUint64
BenchmarkThresholdCompareAsUint64-10    	1000000000	         0.7034 ns/op	       0 B/op	       0 allocs/op
BenchmarkThresholdCompareAsBytes
BenchmarkThresholdCompareAsBytes-10     	191687650	         5.990 ns/op	       0 B/op	       0 allocs/op

jpkrohling · 2023-08-04T18:50:38Z

@jmacd , is this ready for a first review?

pkg/sampling/internal/bytes/randomness.go

pkg/sampling/internal/bytes/threshold.go

github-actions · 2023-08-19T05:20:31Z

This PR was marked stale due to lack of activity. It will be closed in 14 days.

github-actions · 2023-09-03T05:20:29Z

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

jmacd · 2023-12-08T22:07:10Z

Reviewer notes: I am returning this PR to draft mode. I will copy the pkg/sampling package out of this PR and form a new PR with it. After that stuff merges (if we may), then I'll re-open this one.

github-actions · 2023-12-23T05:18:52Z

This PR was marked stale due to lack of activity. It will be closed in 14 days.

github-actions · 2024-01-07T05:19:13Z

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

…29720) **Description:** This is the `pkg/sampling` portion of of #24811. **Link to tracking Issue:** #29738 open-telemetry/opentelemetry-specification#1413 **Testing:** Complete. **Documentation:** New README added. --------- Co-authored-by: Juraci Paixão Kröhling <juraci.github@kroehling.de> Co-authored-by: Kent Quirk <kentquirk@gmail.com>

…pen-telemetry#29720) **Description:** This is the `pkg/sampling` portion of of open-telemetry#24811. **Link to tracking Issue:** open-telemetry#29738 open-telemetry/opentelemetry-specification#1413 **Testing:** Complete. **Documentation:** New README added. --------- Co-authored-by: Juraci Paixão Kröhling <juraci.github@kroehling.de> Co-authored-by: Kent Quirk <kentquirk@gmail.com>

jmacd · 2024-03-21T14:41:51Z

Replaced by #31894.

…rt OTEP 235) (#31894) **Description:** Creates new sampler modes named "equalizing" and "proportional". Preserves existing functionality under the mode named "hash_seed". Fixes #31918 This is the final step in a sequence, the whole of this work was factored into 3+ PRs, including the new `pkg/sampling` and the previous step, #31946. The two new Sampler modes enable mixing OTel sampling SDKs with Collectors in a consistent way. The existing hash_seed mode is also a consistent sampling mode, which makes it possible to have a 1:1 mapping between its decisions and the OTEP 235 randomness and threshold values. Specifically, the 14-bit hash value and sampling probability are mapped into 56-bit R-value and T-value encodings, so that all sampling decisions in all modes include threshold information. This implements the semantic conventions of open-telemetry/semantic-conventions#793, namely the `sampling.randomness` and `sampling.threshold` attributes used for logs where there is no tracestate. The default sampling mode remains HashSeed. We consider a future change of default to Proportional to be desirable, because: 1. Sampling probability is the same, only the hashing algorithm changes 2. Proportional respects and preserves information about earlier sampling decisions, which HashSeed can't do, so it has greater interoperability with OTel SDKs which may also adopt OTEP 235 samplers. **Link to tracking Issue:** Draft for open-telemetry/opentelemetry-specification#3602. Previously #24811, see also open-telemetry/oteps#235 Part of #29738 **Testing:** New testing has been added. **Documentation:** ✅ --------- Co-authored-by: Juraci Paixão Kröhling <juraci.github@kroehling.de>

…rt OTEP 235) (open-telemetry#31894) **Description:** Creates new sampler modes named "equalizing" and "proportional". Preserves existing functionality under the mode named "hash_seed". Fixes open-telemetry#31918 This is the final step in a sequence, the whole of this work was factored into 3+ PRs, including the new `pkg/sampling` and the previous step, open-telemetry#31946. The two new Sampler modes enable mixing OTel sampling SDKs with Collectors in a consistent way. The existing hash_seed mode is also a consistent sampling mode, which makes it possible to have a 1:1 mapping between its decisions and the OTEP 235 randomness and threshold values. Specifically, the 14-bit hash value and sampling probability are mapped into 56-bit R-value and T-value encodings, so that all sampling decisions in all modes include threshold information. This implements the semantic conventions of open-telemetry/semantic-conventions#793, namely the `sampling.randomness` and `sampling.threshold` attributes used for logs where there is no tracestate. The default sampling mode remains HashSeed. We consider a future change of default to Proportional to be desirable, because: 1. Sampling probability is the same, only the hashing algorithm changes 2. Proportional respects and preserves information about earlier sampling decisions, which HashSeed can't do, so it has greater interoperability with OTel SDKs which may also adopt OTEP 235 samplers. **Link to tracking Issue:** Draft for open-telemetry/opentelemetry-specification#3602. Previously open-telemetry#24811, see also open-telemetry/oteps#235 Part of open-telemetry#29738 **Testing:** New testing has been added. **Documentation:** ✅ --------- Co-authored-by: Juraci Paixão Kröhling <juraci.github@kroehling.de>

jmacd added 17 commits May 12, 2023 15:20

Add t-value sampler draft

e822a9b

copy/import tracestate parser package

1bc6017

test ot tracestate

d1fd891

tidy

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renames

bb75f8a

testing two parsers w/ generic code

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integrated

7fa8130

Comments

36230e7

revert two files

7bae35c

Update with r, s, and t-value. Now using regexps and strings.IndexByte()

9010a67

to iterate.

fix sampler build

0e27e40

add support for s-value for non-consistent mode

efcdc3d

WIP

939c758

Merge branch 'main' of github.com:open-telemetry/opentelemetry-collec…

b9a1e56

…tor-contrib into jmacd/tvaluesampler

use new proposed syntax see open-telemetry/opentelemetry-specificatio…

a31266c

…n#3602

update tracestate libs for new encoding

690cd64

wip working on probabilistic sampler with two new modes: downsampler …

c8baf29

…and resampler

github-actions bot added the processor/probabilisticsampler Probabilistic Sampler processor label Aug 2, 2023

github-actions bot requested a review from jpkrohling August 2, 2023 23:35

jmacd added 2 commits August 3, 2023 10:55

unsigned implement split

7f47e4a

two implementations

422e0b2

PeterF778 reviewed Aug 4, 2023

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github-actions bot added the Stale label Aug 19, 2023

github-actions bot closed this Sep 3, 2023

wip

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jmacd closed this Dec 8, 2023

jmacd added 5 commits December 8, 2023 13:23

ProbabilityToThresholdWithPrecision

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test coverage for equalizing and proportional

cc02934

config test

1eecc4a

comments and notes

2159107

update README

e0898a6

jmacd reopened this Dec 8, 2023

jmacd marked this pull request as ready for review December 8, 2023 21:53

jmacd requested a review from a team as a code owner December 8, 2023 21:53

github-actions bot assigned codeboten Dec 8, 2023

jmacd marked this pull request as draft December 8, 2023 22:07

jmacd added a commit to jmacd/opentelemetry-collector-contrib that referenced this pull request Dec 8, 2023

Add comments, README, metadata.yaml relative to open-telemetry#24811

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jmacd mentioned this pull request Dec 8, 2023

Introduce sampling package as reference implementation for OTEP 235 #29720

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jmacd mentioned this pull request Feb 27, 2024

Probability Samplers based on W3C Trace Context Level 2 open-telemetry/opentelemetry-specification#3910

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jmacd mentioned this pull request Mar 21, 2024

[probabilistic sampling processor] encoded sampling probability (support OTEP 235) #31894

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jmacd mentioned this pull request Mar 22, 2024

Update probabilistic sampler processor with OTEP 235 support #31918

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Probabilistic sampler processor based on draft t-value/r-value encoding #24811

Probabilistic sampler processor based on draft t-value/r-value encoding #24811

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Probabilistic sampler processor based on draft t-value/r-value encoding #24811

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