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Fix race in the lastvalue aggregation where 0 could be observed#8056

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dashpole merged 2 commits intoopen-telemetry:mainfrom
dashpole:fix_lastvalue_race
Mar 16, 2026
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Fix race in the lastvalue aggregation where 0 could be observed#8056
dashpole merged 2 commits intoopen-telemetry:mainfrom
dashpole:fix_lastvalue_race

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@dashpole dashpole commented Mar 13, 2026 •
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This initializes the value of the gauge with the correct value before it is stored in the map. We end up storing the same thing twice on the first call, but that isn't a big deal performance-wise.

Discovered during #8021

@dashpole dashpole force-pushed the fix_lastvalue_race branch from 29d663f to b9d4c12 Compare March 13, 2026 20:19
@dashpole dashpole marked this pull request as ready for review March 13, 2026 20:19
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codecov bot commented Mar 13, 2026 •
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Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 81.6%. Comparing base (b201d73) to head (0137964).
⚠️ Report is 1 commits behind head on main.

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@@           Coverage Diff           @@
##            main   #8056     +/-   ##
=======================================
- Coverage   81.6%   81.6%   -0.1%     
=======================================
  Files        304     304             
  Lines      23446   23448      +2     
=======================================
- Hits       19140   19138      -2     
- Misses      3925    3928      +3     
- Partials     381     382      +1
Files with missing lines Coverage Δ
sdk/metric/internal/aggregate/lastvalue.go 100.0% <100.0%> (ø)

... and 2 files with indirect coverage changes

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@dashpole dashpole merged commit 206ac29 into open-telemetry:main Mar 16, 2026
34 checks passed
@dashpole dashpole deleted the fix_lastvalue_race branch March 16, 2026 13:31
@pellared pellared added this to the v1.43.0 milestone Apr 1, 2026
@dmathieu dmathieu mentioned this pull request Apr 2, 2026
Merged
dmathieu added a commit that referenced this pull request Apr 3, 2026
@dmathieu @MrAlias
Release v1.43.0 / v0.65.0 / v0.19.0 (#8128)
9276201 
Release issue:
#8127

## Added

- Add `IsRandom` and `WithRandom` on `TraceFlags`, and `IsRandom` on
`SpanContext` in `go.opentelemetry.io/otel/trace`
for [W3C Trace Context Level 2 Random Trace ID
Flag](https://www.w3.org/TR/trace-context-2/#random-trace-id-flag)
support. (#8012)
- Add service detection with `WithService` in
`go.opentelemetry.io/otel/sdk/resource`. (#7642)
- Add `DefaultWithContext` and `EnvironmentWithContext` in
`go.opentelemetry.io/otel/sdk/resource` to support plumbing
`context.Context` through default and environment detectors. (#8051)
- Support attributes with empty value (`attribute.EMPTY`) in
`go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc`.
(#8038)
- Support attributes with empty value (`attribute.EMPTY`) in
`go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetricgrpc`.
(#8038)
- Support attributes with empty value (`attribute.EMPTY`) in
`go.opentelemetry.io/otel/exporters/otlp/otlplog/otlploggrpc`. (#8038)
- Support attributes with empty value (`attribute.EMPTY`) in
`go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracehttp`.
(#8038)
- Support attributes with empty value (`attribute.EMPTY`) in
`go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetrichttp`.
(#8038)
- Support attributes with empty value (`attribute.EMPTY`) in
`go.opentelemetry.io/otel/exporters/otlp/otlplog/otlploghttp`. (#8038)
- Support attributes with empty value (`attribute.EMPTY`) in
`go.opentelemetry.io/otel/sdk/metric/metricdata/metricdatatest`. (#8038)
- Add support for per-series start time tracking for cumulative metrics
in `go.opentelemetry.io/otel/sdk/metric`.
  Set `OTEL_GO_X_PER_SERIES_START_TIMESTAMPS=true` to enable. (#8060)
- Add `WithCardinalityLimitSelector` for metric reader for configuring
cardinality limits specific to the instrument kind. (#7855)

## Changed

- Introduce the `EMPTY` Type in `go.opentelemetry.io/otel/attribute` to
reflect that an empty value is now a valid value, with `INVALID`
remaining as a deprecated alias of `EMPTY`. (#8038)
- Refactor slice handling in `go.opentelemetry.io/otel/attribute` to
optimize short slice values with fixed-size fast paths. (#8039)
- Improve performance of span metric recording in
`go.opentelemetry.io/otel/sdk/trace` by returning early if
self-observability is not enabled. (#8067)
- Improve formatting of metric data diffs in
`go.opentelemetry.io/otel/sdk/metric/metricdata/metricdatatest`. (#8073)

## Deprecated

- Deprecate `INVALID` in `go.opentelemetry.io/otel/attribute`. Use
`EMPTY` instead. (#8038)

## Fixed

- Return spec-compliant `TraceIdRatioBased` description. This is a
breaking behavioral change, but it is necessary to
make the implementation
[spec-compliant](https://opentelemetry.io/docs/specs/otel/trace/sdk/#traceidratiobased).
(#8027)
- Fix a race condition in `go.opentelemetry.io/otel/sdk/metric` where
the lastvalue aggregation could collect the value 0 even when no
zero-value measurements were recorded. (#8056)
- Limit HTTP response body to 4 MiB in
`go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracehttp` to
mitigate excessive memory usage caused by a misconfigured or malicious
server.
Responses exceeding the limit are treated as non-retryable errors.
(#8108)
- Limit HTTP response body to 4 MiB in
`go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetrichttp` to
mitigate excessive memory usage caused by a misconfigured or malicious
server.
Responses exceeding the limit are treated as non-retryable errors.
(#8108)
- Limit HTTP response body to 4 MiB in
`go.opentelemetry.io/otel/exporters/otlp/otlplog/otlploghttp` to
mitigate excessive memory usage caused by a misconfigured or malicious
server.
Responses exceeding the limit are treated as non-retryable errors.
(#8108)
- `WithHostID` detector in `go.opentelemetry.io/otel/sdk/resource` to
use full path for `kenv` command on BSD. (#8113)
- Fix missing `request.GetBody` in
`go.opentelemetry.io/otel/exporters/otlp/otlplog/otlploghttp` to
correctly handle HTTP2 GOAWAY frame. (#8096)

---------

Co-authored-by: Tyler Yahn <MrAlias@users.noreply.github.com>
@claude claude bot mentioned this pull request Apr 8, 2026
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@dmathieu dmathieu dmathieu approved these changes

@MrAlias MrAlias MrAlias approved these changes

@XSAM XSAM Awaiting requested review from XSAM XSAM is a code owner

@pellared pellared Awaiting requested review from pellared pellared is a code owner

@flc1125 flc1125 Awaiting requested review from flc1125 flc1125 is a code owner

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