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promql: fix smoothed interpolation across counter resets#17988

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roidelapluie merged 1 commit intoprometheus:mainfrom
roidelapluie:roidelapluie/fixsmoothing
Feb 2, 2026
Merged

promql: fix smoothed interpolation across counter resets#17988
roidelapluie merged 1 commit intoprometheus:mainfrom
roidelapluie:roidelapluie/fixsmoothing

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Fix incorrect interpolation when counter resets occur in smoothed range selector evaluation. Previously, the asymmetric handling of counter resets (y1=0 on left edge, y2+=y1 on right edge) produced wrong values.

Now uniformly set y1=0 when a counter reset is detected, correctly modeling the counter as starting from 0 post-reset.

This fixes rate calculations across counter resets. For example, rate(metric[10s] smoothed) where metric goes from 100 to 10 (a reset) now correctly computes 0.666... by treating the counter as resetting to 0 rather than producing inflated values from the old behavior.

Which issue(s) does the PR fix:

Does this PR introduce a user-facing change?

[BUGFIX] PromQL: Fix smoothed interpolation across counter resets

Fix incorrect interpolation when counter resets occur in smoothed range
selector evaluation. Previously, the asymmetric handling of counter
resets (y1=0 on left edge, y2+=y1 on right edge) produced wrong values.

Now uniformly set y1=0 when a counter reset is detected, correctly
modeling the counter as starting from 0 post-reset.

This fixes rate calculations across counter resets. For example,
rate(metric[10s] smoothed) where metric goes from 100 to 10 (a reset)
now correctly computes 0.666... by treating the counter as resetting
to 0 rather than producing inflated values from the old behavior.

Signed-off-by: Julien Pivotto <[email protected]>
@roidelapluie roidelapluie requested a review from a team as a code owner February 2, 2026 10:56
@roidelapluie roidelapluie requested a review from ywwg February 2, 2026 10:56
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LGTM. Seems obvious in hindsight.

@roidelapluie roidelapluie merged commit 717d37b into prometheus:main Feb 2, 2026
52 of 54 checks passed
roidelapluie added a commit to grafana/mimir that referenced this pull request Feb 5, 2026
The upstream Prometheus change (prometheus/prometheus#17988) fixed
incorrect interpolation when counter resets occur in smoothed range
selector evaluation. The old behavior asymmetrically handled counter
resets (y1=0 on left edge, y2+=y1 on right edge) which produced wrong
values.

The fix uniformly sets y1=0 when a counter reset is detected, correctly
modeling the counter as starting from 0 post-reset. This updates our
interpolate function to match the new behavior by removing the leftEdge
parameter and adjusting test expectations accordingly.

Signed-off-by: Julien Pivotto <[email protected]>
roidelapluie added a commit to grafana/mimir that referenced this pull request Feb 5, 2026
The upstream Prometheus change (prometheus/prometheus#17988) fixed
incorrect interpolation when counter resets occur in smoothed range
selector evaluation. The old behavior asymmetrically handled counter
resets (y1=0 on left edge, y2+=y1 on right edge) which produced wrong
values.

The fix uniformly sets y1=0 when a counter reset is detected, correctly
modeling the counter as starting from 0 post-reset. This updates our
interpolate function to match the new behavior by removing the leftEdge
parameter and adjusting test expectations accordingly.

Signed-off-by: Julien Pivotto <[email protected]>
roidelapluie added a commit to grafana/mimir that referenced this pull request Feb 5, 2026
The upstream Prometheus change (prometheus/prometheus#17988) fixed
incorrect interpolation when counter resets occur in smoothed range
selector evaluation. The old behavior asymmetrically handled counter
resets (y1=0 on left edge, y2+=y1 on right edge) which produced wrong
values.

The fix uniformly sets y1=0 when a counter reset is detected, correctly
modeling the counter as starting from 0 post-reset. This updates our
interpolate function to match the new behavior by removing the leftEdge
parameter and adjusting test expectations accordingly.

Signed-off-by: Julien Pivotto <[email protected]>
roidelapluie added a commit to grafana/mimir that referenced this pull request Feb 5, 2026
The upstream Prometheus change (prometheus/prometheus#17988) fixed
incorrect interpolation when counter resets occur in smoothed range
selector evaluation. The old behavior asymmetrically handled counter
resets (y1=0 on left edge, y2+=y1 on right edge) which produced wrong
values.

The fix uniformly sets y1=0 when a counter reset is detected, correctly
modeling the counter as starting from 0 post-reset. This updates our
interpolate function to match the new behavior by removing the leftEdge
parameter and adjusting test expectations accordingly.

Signed-off-by: Julien Pivotto <[email protected]>
renovate bot added a commit to sdwilsh/ansible-playbooks that referenced this pull request Mar 12, 2026
##### [\`v3.10.0\`](https://github.com/prometheus/prometheus/releases/tag/v3.10.0)

Prometheus now offers a distroless Docker image variant alongside the default
busybox image. The distroless variant provides enhanced security with a minimal
base image, uses UID/GID 65532 (nonroot) instead of nobody, and removes the
VOLUME declaration. Both variants are available with `-busybox` and `-distroless`
tag suffixes (e.g., `prom/prometheus:latest-busybox`, `prom/prometheus:latest-distroless`).
The busybox image remains the default with no suffix for backwards compatibility
(e.g., `prom/prometheus:latest` points to the busybox variant).

For users migrating existing **named** volumes from the busybox image to the distroless variant, the ownership can be adjusted with:

```
docker run --rm -v prometheus-data:/prometheus alpine chown -R 65532:65532 /prometheus
```

Then, the container can be started with the old volume with:

```
docker run -v prometheus-data:/prometheus prom/prometheus:latest-distroless
```

User migrating from bind mounts might need to ajust permissions too, depending on their setup.

- \[CHANGE] Alerting: Add `alertmanager` dimension to following metrics: `prometheus_notifications_dropped_total`, `prometheus_notifications_queue_capacity`, `prometheus_notifications_queue_length`. [#16355](prometheus/prometheus#16355)
- \[CHANGE] UI: Hide expanded alert annotations by default, enabling more information density on the `/alerts` page. [#17611](prometheus/prometheus#17611)
- \[FEATURE] AWS SD: Add MSK Role. [#17600](prometheus/prometheus#17600)
- \[FEATURE] PromQL: Add `fill()` / `fill_left()` / `fill_right()` binop modifiers for specifying default values for missing series. [#17644](prometheus/prometheus#17644)
- \[FEATURE] Web: Add OpenAPI 3.2 specification for the HTTP API at `/api/v1/openapi.yaml`. [#17825](prometheus/prometheus#17825)
- \[FEATURE] Dockerfile: Add distroless image variant using UID/GID 65532 and no VOLUME declaration. Busybox image remains default. [#17876](prometheus/prometheus#17876)
- \[FEATURE] Web: Add on-demand wall time profiling under `<URL>/debug/pprof/fgprof`. [#18027](prometheus/prometheus#18027)
- \[ENHANCEMENT] PromQL: Add more detail to histogram quantile monotonicity info annotations. [#15578](prometheus/prometheus#15578)
- \[ENHANCEMENT] Alerting: Independent alertmanager sendloops. [#16355](prometheus/prometheus#16355)
- \[ENHANCEMENT] TSDB: Experimental support for early compaction of stale series in the memory with configurable threshold `stale_series_compaction_threshold` in the config file. [#16929](prometheus/prometheus#16929)
- \[ENHANCEMENT] Service Discovery: Service discoveries are now removable from the Prometheus binary through the Go build tag `remove_all_sd` and individual service discoveries can be re-added with the build tags `enable_<sd name>_sd`. Users can build a custom Prometheus with only the necessary SDs for a smaller binary size. [#17736](prometheus/prometheus#17736)
- \[ENHANCEMENT] Promtool: Support promql syntax features `promql-duration-expr` and `promql-extended-range-selectors`. [#17926](prometheus/prometheus#17926)
- \[PERF] PromQL: Avoid unnecessary label extraction in PromQL functions. [#17676](prometheus/prometheus#17676)
- \[PERF] PromQL: Improve performance of regex matchers like `.*-.*-.*`. [#17707](prometheus/prometheus#17707)
- \[PERF] OTLP: Add label caching for OTLP-to-Prometheus conversion to reduce allocations and improve latency. [#17860](prometheus/prometheus#17860)
- \[PERF] API: Compute `/api/v1/targets/relabel_steps` in a single pass instead of re-running relabeling for each prefix. [#17969](prometheus/prometheus#17969)
- \[PERF] tsdb: Optimize LabelValues intersection performance for matchers. [#18069](prometheus/prometheus#18069)
- \[BUGFIX] PromQL: Prevent query strings containing only UTF-8 continuation bytes from crashing Prometheus. [#17735](prometheus/prometheus#17735)
- \[BUGFIX] Web: Fix missing `X-Prometheus-Stopping` header for `/-/ready` endpoint in `NotReady` state. [#17795](prometheus/prometheus#17795)
- \[BUGFIX] PromQL: Fix PromQL `info()` function returning empty results when filtering by a label that exists on both the input metric and `target_info`. [#17817](prometheus/prometheus#17817)
- \[BUGFIX] TSDB: Fix a bug during exemplar buffer grow/shrink that could cause exemplars to be incorrectly discarded. [#17863](prometheus/prometheus#17863)
- \[BUGFIX] UI: Fix broken graph display after page reload, due to broken Y axis min encoding/decoding. [#17869](prometheus/prometheus#17869)
- \[BUGFIX] TSDB: Fix memory leaks in buffer pools by clearing reference fields (Labels, Histogram pointers, metadata strings) before returning buffers to pools. [#17879](prometheus/prometheus#17879)
- \[BUGFIX] PromQL: info function: fix series without identifying labels not being returned. [#17898](prometheus/prometheus#17898)
- \[BUGFIX] OTLP: Filter `__name__` from OTLP attributes to prevent duplicate labels. [#17917](prometheus/prometheus#17917)
- \[BUGFIX] TSDB: Fix division by zero when computing stale series ratio with empty head. [#17952](prometheus/prometheus#17952)
- \[BUGFIX] OTLP: Fix potential silent data loss for sum metrics. [#17954](prometheus/prometheus#17954)
- \[BUGFIX] PromQL: Fix smoothed interpolation across counter resets. [#17988](prometheus/prometheus#17988)
- \[BUGFIX] PromQL: Fix panic with `@` modifier on empty ranges. [#18020](prometheus/prometheus#18020)
- \[BUGFIX] PromQL: Fix `avg_over_time` for a single native histogram. [#18058](prometheus/prometheus#18058)
renovate bot added a commit to sdwilsh/ansible-playbooks that referenced this pull request Mar 13, 2026
##### [\`v3.10.0\`](https://github.com/prometheus/prometheus/releases/tag/v3.10.0)

Prometheus now offers a distroless Docker image variant alongside the default
busybox image. The distroless variant provides enhanced security with a minimal
base image, uses UID/GID 65532 (nonroot) instead of nobody, and removes the
VOLUME declaration. Both variants are available with `-busybox` and `-distroless`
tag suffixes (e.g., `prom/prometheus:latest-busybox`, `prom/prometheus:latest-distroless`).
The busybox image remains the default with no suffix for backwards compatibility
(e.g., `prom/prometheus:latest` points to the busybox variant).

For users migrating existing **named** volumes from the busybox image to the distroless variant, the ownership can be adjusted with:

```
docker run --rm -v prometheus-data:/prometheus alpine chown -R 65532:65532 /prometheus
```

Then, the container can be started with the old volume with:

```
docker run -v prometheus-data:/prometheus prom/prometheus:latest-distroless
```

User migrating from bind mounts might need to ajust permissions too, depending on their setup.

- \[CHANGE] Alerting: Add `alertmanager` dimension to following metrics: `prometheus_notifications_dropped_total`, `prometheus_notifications_queue_capacity`, `prometheus_notifications_queue_length`. [#16355](prometheus/prometheus#16355)
- \[CHANGE] UI: Hide expanded alert annotations by default, enabling more information density on the `/alerts` page. [#17611](prometheus/prometheus#17611)
- \[FEATURE] AWS SD: Add MSK Role. [#17600](prometheus/prometheus#17600)
- \[FEATURE] PromQL: Add `fill()` / `fill_left()` / `fill_right()` binop modifiers for specifying default values for missing series. [#17644](prometheus/prometheus#17644)
- \[FEATURE] Web: Add OpenAPI 3.2 specification for the HTTP API at `/api/v1/openapi.yaml`. [#17825](prometheus/prometheus#17825)
- \[FEATURE] Dockerfile: Add distroless image variant using UID/GID 65532 and no VOLUME declaration. Busybox image remains default. [#17876](prometheus/prometheus#17876)
- \[FEATURE] Web: Add on-demand wall time profiling under `<URL>/debug/pprof/fgprof`. [#18027](prometheus/prometheus#18027)
- \[ENHANCEMENT] PromQL: Add more detail to histogram quantile monotonicity info annotations. [#15578](prometheus/prometheus#15578)
- \[ENHANCEMENT] Alerting: Independent alertmanager sendloops. [#16355](prometheus/prometheus#16355)
- \[ENHANCEMENT] TSDB: Experimental support for early compaction of stale series in the memory with configurable threshold `stale_series_compaction_threshold` in the config file. [#16929](prometheus/prometheus#16929)
- \[ENHANCEMENT] Service Discovery: Service discoveries are now removable from the Prometheus binary through the Go build tag `remove_all_sd` and individual service discoveries can be re-added with the build tags `enable_<sd name>_sd`. Users can build a custom Prometheus with only the necessary SDs for a smaller binary size. [#17736](prometheus/prometheus#17736)
- \[ENHANCEMENT] Promtool: Support promql syntax features `promql-duration-expr` and `promql-extended-range-selectors`. [#17926](prometheus/prometheus#17926)
- \[PERF] PromQL: Avoid unnecessary label extraction in PromQL functions. [#17676](prometheus/prometheus#17676)
- \[PERF] PromQL: Improve performance of regex matchers like `.*-.*-.*`. [#17707](prometheus/prometheus#17707)
- \[PERF] OTLP: Add label caching for OTLP-to-Prometheus conversion to reduce allocations and improve latency. [#17860](prometheus/prometheus#17860)
- \[PERF] API: Compute `/api/v1/targets/relabel_steps` in a single pass instead of re-running relabeling for each prefix. [#17969](prometheus/prometheus#17969)
- \[PERF] tsdb: Optimize LabelValues intersection performance for matchers. [#18069](prometheus/prometheus#18069)
- \[BUGFIX] PromQL: Prevent query strings containing only UTF-8 continuation bytes from crashing Prometheus. [#17735](prometheus/prometheus#17735)
- \[BUGFIX] Web: Fix missing `X-Prometheus-Stopping` header for `/-/ready` endpoint in `NotReady` state. [#17795](prometheus/prometheus#17795)
- \[BUGFIX] PromQL: Fix PromQL `info()` function returning empty results when filtering by a label that exists on both the input metric and `target_info`. [#17817](prometheus/prometheus#17817)
- \[BUGFIX] TSDB: Fix a bug during exemplar buffer grow/shrink that could cause exemplars to be incorrectly discarded. [#17863](prometheus/prometheus#17863)
- \[BUGFIX] UI: Fix broken graph display after page reload, due to broken Y axis min encoding/decoding. [#17869](prometheus/prometheus#17869)
- \[BUGFIX] TSDB: Fix memory leaks in buffer pools by clearing reference fields (Labels, Histogram pointers, metadata strings) before returning buffers to pools. [#17879](prometheus/prometheus#17879)
- \[BUGFIX] PromQL: info function: fix series without identifying labels not being returned. [#17898](prometheus/prometheus#17898)
- \[BUGFIX] OTLP: Filter `__name__` from OTLP attributes to prevent duplicate labels. [#17917](prometheus/prometheus#17917)
- \[BUGFIX] TSDB: Fix division by zero when computing stale series ratio with empty head. [#17952](prometheus/prometheus#17952)
- \[BUGFIX] OTLP: Fix potential silent data loss for sum metrics. [#17954](prometheus/prometheus#17954)
- \[BUGFIX] PromQL: Fix smoothed interpolation across counter resets. [#17988](prometheus/prometheus#17988)
- \[BUGFIX] PromQL: Fix panic with `@` modifier on empty ranges. [#18020](prometheus/prometheus#18020)
- \[BUGFIX] PromQL: Fix `avg_over_time` for a single native histogram. [#18058](prometheus/prometheus#18058)
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