@prometheus-io/lezer-promql/CHANGELOG.md

lezer-based PromQL grammar

# Changelog

## main / unreleased

## 3.8.0-rc.0 / 2025-11-07

* [CHANGE] TSDB: Native Histogram Custom Bounds with a NaN threshold are now rejected. #17287
* [FEATURE] Dockerfile: Add OpenContainers spec labels to Dockerfile. #16483
* [FEATURE] SD: Add unified AWS service discovery for ec2, lightsail and ecs services. #17046
* [FEATURE] Native histograms are now a stable, but optional feature, use the `scrape_native_histogram` config setting. #17232 #17315
* [FEATURE] UI: Support anchored and smoothed keyword in promql editor. #17239
* [FEATURE] UI: Show detailed relabeling steps for each discovered target. #17337
* [FEATURE] Alerting: Add urlQueryEscape to template functions. #17403
* [FEATURE] Promtool: Add  Remote-Write 2.0 support to `promtool push metrics` via the `--protobuf_message` flag. #17417
* [ENHANCEMENT] Clarify the docs about handling negative native histograms.  #17249
* [ENHANCEMENT] Mixin: Add static UID to the remote-write dashboard. #17256
* [ENHANCEMENT] PromQL: Reconcile mismatched NHCB bounds in `Add` and `Sub`. #17278
* [ENHANCEMENT] Alerting: Add "unknown" state for alerting rules that haven't been evaluated yet. #17282
* [ENHANCEMENT] Scrape: Allow simultaneous use of classic histogram → NHCB conversion and zero-timestamp ingestion. #17305
* [ENHANCEMENT] UI: Add smoothed/anchored in explain. #17334
* [ENHANCEMENT] OTLP: De-duplicate any `target_info` samples with the same timestamp for the same series. #17400
* [ENHANCEMENT] Document `use_fips_sts_endpoint` in `sigv4` config sections. #17304
* [ENHANCEMENT] Document Prometheus Agent. #14519
* [PERF] PromQL: Speed up parsing of variadic functions. #17316
* [PERF] UI: Speed up alerts/rules/... pages by not rendering collapsed content. #17485
* [PERF] UI: Performance improvement when getting label name and values in promql editor. #17194
* [PERF] UI: Speed up /alerts for many firing alerts via virtual scrolling.  #17254
* [BUGFIX] PromQL: Fix slice indexing bug in info function on churning series. #17199
* [BUGFIX] API: Reduce lock contention on `/api/v1/targets`. #17306
* [BUGFIX] PromQL: Consistent handling of gauge vs. counter histograms in aggregations. #17312
* [BUGFIX] TSDB: Allow NHCB with -Inf as the first custom value. #17320
* [BUGFIX] UI: Fix duplicate loading of data from the API speed up rendering of some pages. #17357
* [BUGFIX] Old UI: Fix createExpressionLink to correctly build /graph URLs so links from Alerts/Rules work again. #17365
* [BUGFIX] PromQL: Avoid panic when parsing malformed `info` call. #17379
* [BUGFIX] PromQL: Include histograms when enforcing sample_limit. #17390
* [BUGFIX] Config: Fix panic if TLS CA file is absent. #17418
* [BUGFIX] PromQL: Fix `histogram_fraction` for classic histograms and NHCB if lower bound is in the first bucket. #17424

## 3.7.3 / 2025-10-29

* [BUGFIX] UI: Revert changed (and breaking) redirect behavior for `-web.external-url` if `-web.route-prefix` is configured, which was introduced in #17240. #17389
* [BUGFIX] Fix federation of some native histograms. #17299 #17409
* [BUGFIX] promtool: `check config` would fail when `--lint=none` flag was set. #17399 #17414
* [BUGFIX] Remote-write: fix a deadlock in the queue resharding logic that can lead to suboptimal queue behavior. #17412

## 3.7.2 / 2025-10-22

* [BUGFIX] AWS SD: Fix AWS SDK v2 credentials handling for EC2 and Lightsail discovery. #17355
* [BUGFIX] AWS SD: Load AWS region from IMDS when not set. #17376
* [BUGFIX] Relabeling: Fix `labelmap` action validation with the legacy metric name validation scheme. #17372
* [BUGFIX] PromQL: Fix parsing failure when `anchored` and `smoothed` are used as metric names and label names. #17353
* [BUGFIX] PromQL: Fix formatting of range vector selectors with `smoothed`/`anchored` modifier. #17354

## 3.7.1 / 2025-10-16

* [BUGFIX] OTLP: Prefix `key_` to label name when translating an OTel attribute name starting with a single underscore, and keep multiple consecutive underscores in label name when translating an OTel attribute name. This reverts the breaking changes introduced in 3.7.0. #17344

## 3.7.0 / 2025-10-15

* [CHANGE] Remote-write: the following metrics are deprecated:
   - `prometheus_remote_storage_samples_in_total`, use `prometheus_wal_watcher_records_read_total{type="samples"}` and `prometheus_remote_storage_samples_dropped_total` instead,
   - `prometheus_remote_storage_histograms_in_total`, use `prometheus_wal_watcher_records_read_total{type=~".*histogram_samples"}` and `prometheus_remote_storage_histograms_dropped_total` instead,
   - `prometheus_remote_storage_exemplars_in_total`, use `prometheus_wal_watcher_records_read_total{type="exemplars"}` and `prometheus_remote_storage_exemplars_dropped_total` instead,
   - `prometheus_remote_storage_highest_timestamp_in_seconds`, use the more accurate `prometheus_remote_storage_queue_highest_timestamp_seconds` instead in dashboards and alerts to properly account for relabeling and for more accuracy. #17065
* [FEATURE] PromQL: Add support for experimental anchored and smoothed rate behind feature flag `promql-extended-range-selectors`. #16457
* [FEATURE] Federation: Add support for native histograms with custom buckets (NHCB). #17215
* [FEATURE] PromQL: Add `first_over_time(...)` and `ts_of_first_over_time(...)` behind feature flag `experimental-promql-functions`. #16963 #17021
* [FEATURE] Remote-write: Add support for Azure Workload Identity as an authentication method for the receiver. #16788
* [FEATURE] Remote-write: Add type and unit labels to outgoing time series in remote-write 2.0 when the `type-and-unit-labels` feature flag is enabled. #17033
* [FEATURE] OTLP: Write start time of metrics as created time zero samples into TSDB when `created-timestamp-zero-ingestion` feature flag is enabled. #16951
* [ENHANCEMENT] PromQL: Add warn-level annotations for counter reset conflicts in certain histogram operations. #17051 #17094
* [ENHANCEMENT] UI: Add scrape interval and scrape timeout to targets page. #17158
* [ENHANCEMENT] TSDB: Reduce the resolution of native histograms read from chunks or remote read if the schema is exponential. #17213
* [ENHANCEMENT] Remote write: Add logging for unexpected metadata in sample batches, when metadata entries are found in samples-only batches. #17034 #17082
* [ENHANCEMENT] Rules: Support concurrent evaluation for rules querying `ALERTS` and `ALERTS_FOR_STATE`. #17064
* [ENHANCEMENT] TSDB: Add logs to improve visibility into internal operations. #17074
* [PERF] OTLP: Write directly to TSDB instead of passing through a Remote-Write adapter when receiving OTLP metrics. #16951
* [PERF] OTLP: Reduce number of logs emitted from OTLP endpoint. No need to log duplicate sample errors. #17201
* [PERF] PromQL: Move more work to preprocessing step. #16896
* [PERF] PromQL: Reduce allocations when walking the syntax tree. #16593
* [PERF] TSDB: Optimize appender creation, slightly speeding up startup. #16922
* [PERF] TSDB: Improve speed of querying a series with multiple matchers. #13971
* [BUGFIX] Alerting: Mutating alerts relabeling (using `replace` actions, etc.) within a `alertmanager_config.alert_relabel_configs` block is now scoped correctly and no longer yields altered alerts to subsequent blocks. #17063
* [BUGFIX] Config: Infer valid escaping scheme when scrape config validation scheme is set. #16923
* [BUGFIX] TSDB: Correctly handle appending mixed-typed samples to the same series. #17071 #17241 #17290 #17295 #17296
* [BUGFIX] Remote-write: Prevent sending unsupported native histograms with custom buckets (NHCB) over Remote-write 1.0, log warning. #17146
* [BUGFIX] TSDB: Fix metadata entries handling on `metadata-wal-records` experimental feature for native histograms with custom buckets (NHCB) in protobuf scraping. #17156
* [BUGFIX] TSDB: Ignore Native Histograms with invalid schemas during WAL/WBL replay. #17214
* [BUGFIX] PromQL: Avoid empty metric names in annotations for `histogram_quantile()`. #16794
* [BUGFIX] PromQL: Correct inaccurate character positions in errors for some aggregate expressions. #16996 #17031
* [BUGFIX] PromQL: Fix `info()` function on churning series. #17135
* [BUGFIX] PromQL: Set native histogram to gauge type when subtracting or multiplying/dividing with negative factors. #17004
* [BUGFIX] TSDB: Reject unsupported native histogram schemas when attempting to append to TSDB. For scrape and remote-write implement reducing the resolution to fit the maximum if the schema is within the -9 to 52. #17189
* [BUGFIX] Remote-write: Fix HTTP handler to return after writing error response for invalid compression. #17050
* [BUGFIX] Remote-write: Return HTTP error `400` instead of `5xx` for wrongly formatted Native Histograms. #17210
* [BUGFIX] Scrape: Prevent staleness markers from generating unnecessary series. #16429
* [BUGFIX] TSDB: Avoid misleading `Failed to calculate size of \"wal\" dir` error logs during WAL clean-up. #17006
* [BUGFIX] TSDB: Prevent erroneously dropping series records during WAL checkpoints. #17029
* [BUGFIX] UI: Fix redirect to path of `-web.external-url` if `-web.route-prefix` is configured. #17240
* [BUGFIX] Remote-write: Do not panic on invalid symbol table in remote-write 2.0. #17160

## 3.6.0 / 2025-09-17

* [FEATURE] PromQL: Add `step()`, and `min()` and `max()` on durations, behind feature flag `promql-duration-expr`. #16777
* [FEATURE] API: Add a `/v1/status/tsdb/blocks` endpoint exposing metadata about loaded blocks. #16695
* [FEATURE] Templates: Add `toDuration()` and `now()` functions. #16619
* [ENHANCEMENT] Discovery: Add support for attaching namespace metadata to targets. #16831
* [ENHANCEMENT] OTLP: Support new `UnderscoreEscapingWithoutSuffixes` strategy via `otlp.translation_strategy`. #16849
* [ENHANCEMENT] OTLP: Support including scope metadata as metric labels via `otlp.promote_scope_metadata`. #16878
* [ENHANCEMENT] OTLP: Add `__type__` and `__unit__` labels when feature flag `type-and-unit-labels` is enabled. #16630
* [ENHANCEMENT] Tracing: Send the traceparent HTTP header during scrapes. #16425
* [ENHANCEMENT] UI: Add option to disable info and warning query messages under `Query page settings`. #16901
* [ENHANCEMENT] UI: Improve metadata handling for `_count/_sum/_bucket` suffixes. #16910
* [ENHANCEMENT] TSDB: Track stale series in the Head block via the `prometheus_tsdb_head_stale_series` metric. #16925
* [PERF] PromQL: Improve performance due to internal optimizations. #16797
* [BUGFIX] Config: Fix "unknown global name escaping method" error messages produced during config validation. #16801
* [BUGFIX] Discovery: Fix race condition during shutdown. #16820
* [BUGFIX] OTLP: Generate `target_info` samples between the earliest and latest samples per resource. #16737
* [BUGFIX] PromQL: Fail when `NaN` is passed as parameter to `topk()`, `bottomk()`, `limitk()` and `limit_ratio()`. #16725
* [BUGFIX] PromQL: Fix extrapolation for native counter histograms. #16828
* [BUGFIX] PromQL: Reduce numerical errors by disabling some optimizations. #16895
* [BUGFIX] PromQL: Fix inconsistencies when using native histograms in subqueries. #16879
* [BUGFIX] PromQL: Fix inconsistent annotations for `rate()` and `increase()` on histograms when feature flag `type-and-unit-labels` is enabled. #16915
* [BUGFIX] Scraping: Fix memory corruption in `slicelabels` builds. #16946
* [BUGFIX] TSDB: Fix panic on append when feature flag `created-timestamp-zero-ingestion` is enabled. #16332
* [BUGFIX] TSDB: Fix panic on append for native histograms with empty buckets. #16893

## 3.5.0 / 2025-07-14

* [FEATURE] PromQL: Add experimental type and unit metadata labels, behind feature flag `type-and-unit-labels`. #16228 #16632 #16718 #16743
* [FEATURE] PromQL: Add `ts_of_(min|max|last)_over_time`, behind feature flag `experimental-promql-functions`. #16722 #16733
* [FEATURE] Scraping: Add global option `always_scrape_classic_histograms` to scrape a classic histogram even if it is also exposed as native. #16452
* [FEATURE] OTLP: New config options `promote_all_resource_attributes` and `ignore_resource_attributes`. #16426
* [FEATURE] Discovery: New service discovery for STACKIT Cloud. #16401
* [ENHANCEMENT] Hetzner SD: Add `label_selector` to filter servers. #16512
* [ENHANCEMENT] PromQL: support non-constant parameter in aggregations like `quantile` and `topk`. #16404
* [ENHANCEMENT] UI: Better total target count display when using `keep_dropped_targets` option. #16604
* [ENHANCEMENT] UI: Add simple filtering on the `/rules` page. #16605
* [ENHANCEMENT] UI: Display query stats in hover tooltip over table query tab. #16723
* [ENHANCEMENT] UI: Clear search field on `/targets` page. #16567
* [ENHANCEMENT] Rules: Check that rules parse without error earlier at startup. #16601
* [ENHANCEMENT] Promtool: Optional fuzzy float64 comparison in rules unittests. #16395
* [PERF] PromQL: Reuse `histogramStatsIterator` where possible. #16686
* [PERF] PromQL: Reuse storage for custom bucket values for native histograms. #16565
* [PERF] UI: Optimize memoization and search debouncing on `/targets` page. #16589
* [PERF] UI: Fix full-page re-rendering when opening status nav menu. #16590
* [PERF] Kubernetes SD: use service cache.Indexer to achieve better performance. #16365
* [PERF] TSDB: Optionally use Direct IO for chunks writing. #15365
* [PERF] TSDB: When fetching label values, stop work earlier if the limit is reached. #16158
* [PERF] Labels: Simpler/faster stringlabels encoding. #16069
* [PERF] Scraping: Reload scrape pools concurrently. #16595 #16783
* [BUGFIX] Top-level: Update GOGC before loading TSDB. #16491
* [BUGFIX] Config: Respect GOGC environment variable if no "runtime" block exists. #16558
* [BUGFIX] PromQL: Fix native histogram `last_over_time`. #16744
* [BUGFIX] PromQL: Fix reported parser position range in errors for aggregations wrapped in ParenExpr #16041 #16754
* [BUGFIX] PromQL: Don't emit a value from `histogram_fraction` or `histogram_quantile` if classic and native histograms are present at the same timestamp. #16552
* [BUGFIX] PromQL: Incorrect rounding of `[1001ms]` to `[1s]` and similar. #16478
* [BUGFIX] PromQL: Fix inconsistent / sometimes negative `histogram_count` and `histogram_sum`. #16682
* [BUGFIX] PromQL: Improve handling of NaNs in native histograms. #16724
* [BUGFIX] PromQL: Fix unary operator precedence in duration expressions. #16713
* [BUGFIX] PromQL: Improve consistency of `avg` aggregation and `avg_over_time`. #16569 #16773
* [BUGFIX] UI: Add query warnings and info to graph view. #16753 #16759
* [BUGFIX] API: Add HTTP `Vary: Origin` header to responses to avoid cache poisoning. #16008
* [BUGFIX] Discovery: Avoid deadlocks by taking locks in consistent order. #16587
* [BUGFIX] Remote-write: For Azure AD auth, allow empty `client_id` to suppport system assigned managed identity. #16421
* [BUGFIX] Scraping: Fix rare memory corruption bug. #16623
* [BUGFIX] Scraping: continue handling custom-bucket histograms after an exponential histogram is encountered. #16720
* [BUGFIX] OTLP: Default config not respected when `otlp:` block is unset. #16693

## 3.4.2 / 2025-06-26

* [BUGFIX] OTLP receiver: Fix default configuration not being respected if the `otlp:` block is unset in the config file. #16693

## 3.4.1 / 2025-05-31

* [BUGFIX] Parser: Add reproducer for a dangling-reference issue in parsers. #16633

## 3.4.0 / 2025-05-17

* [CHANGE] Config: Make setting out-of-order native histograms feature (`--enable-feature=ooo-native-histograms`) a no-op. Out-of-order native histograms are now always enabled when `out_of_order_time_window` is greater than zero and `--enable-feature=native-histograms` is set. #16207
* [FEATURE] OTLP translate: Add feature flag for optionally translating OTel explicit bucket histograms into native histograms with custom buckets. #15850
* [FEATURE] OTLP translate: Add option to receive OTLP metrics without translating names or attributes. #16441
* [FEATURE] PromQL: allow arithmetic operations in durations in PromQL parser. #16249
* [FEATURE] OTLP receiver: Add primitive support for ingesting OTLP delta metrics as-is. #16360
* [ENHANCEMENT] PromQL: histogram_fraction for bucket histograms. #16095
* [ENHANCEMENT] TSDB: add `prometheus_tsdb_wal_replay_unknown_refs_total` and `prometheus_tsdb_wbl_replay_unknown_refs_total` metrics to track unknown series references during WAL/WBL replay. #16166
* [ENHANCEMENT] Scraping: Add config option for escaping scheme request. #16066
* [ENHANCEMENT] Config: Add global config option for convert_classic_histograms_to_nhcb. #16226
* [ENHANCEMENT] Alerting: make batch size configurable (`--alertmanager.notification-batch-size`). #16254
* [PERF] Kubernetes SD: make endpointSlice discovery more efficient. #16433
* [BUGFIX] Config: Fix auto-reload on changes to rule and scrape config files. #16340
* [BUGFIX] Scraping: Skip native histogram series if ingestion is disabled. #16218
* [BUGFIX] TSDB: Handle metadata/tombstones/exemplars for duplicate series during WAL replay. #16231
* [BUGFIX] TSDB: Avoid processing exemplars outside the valid time range during WAL replay. #16242
* [BUGFIX] Promtool: Add feature flags for PromQL features. #16443
* [BUGFIX] Rules: correct logging of alert name & template data. #15093
* [BUGFIX] PromQL: Use arithmetic mean for `histogram_stddev()` and `histogram_stdvar()` . #16444

## 3.3.0 / 2025-04-15

* [FEATURE] PromQL: Implement `idelta()` and `irate()` for native histograms. #15853
* [ENHANCEMENT] Scaleway SD: Add `__meta_scaleway_instance_public_ipv4_addresses` and `__meta_scaleway_instance_public_ipv6_addresses` labels. #14228
* [ENHANCEMENT] TSDB: Reduce locking while reloading blocks. #12920
* [ENHANCEMENT] PromQL: Allow UTF-8 labels in `label_replace()`. #15974
* [ENHANCEMENT] Promtool: `tsdb create-blocks-from openmetrics` can now read from a Pipe. #16011
* [ENHANCEMENT] Rules: Add support for anchors and aliases in rule files. #14957
* [ENHANCEMENT] Dockerfile: Make `/prometheus` writable. #16073
* [ENHANCEMENT] API: Include scrape pool name for dropped targets in `/api/v1/targets`. #16085
* [ENHANCEMENT] UI: Improve time formatting and copying of selectors. #15999 #16165
* [ENHANCEMENT] UI: Bring back vertical grid lines and graph legend series toggling instructions. #16163 #16164
* [ENHANCEMENT] Mixin: The `cluster` label can be customized using `clusterLabel`. #15826
* [PERF] TSDB: Optimize some operations on head chunks by taking shortcuts. #12659
* [PERF] TSDB & Agent: Reduce memory footprint during WL replay. #15778
* [PERF] Remote-Write: Reduce memory footprint during WAL replay. #16197
* [PERF] API: Reduce memory footprint during header parsing. #16001
* [PERF] Rules: Improve dependency evaluation, enabling better concurrency. #16039
* [PERF] Scraping: Improve scraping performance for native histograms. #15731
* [PERF] Scraping: Improve parsing of created timestamps. #16072
* [BUGFIX] Scraping: Bump cache iteration after error to avoid false duplicate detections. #16174
* [BUGFIX] Scraping: Skip native histograms series when ingestion is disabled. #16218
* [BUGFIX] PromQL: Fix counter reset detection for native histograms. #15902 #15987
* [BUGFIX] PromQL: Fix inconsistent behavior with an empty range. #15970
* [BUGFIX] PromQL: Fix inconsistent annotation in `quantile_over_time()`. #16018
* [BUGFIX] PromQL: Prevent `label_join()` from producing duplicates. #15975
* [BUGFIX] PromQL: Ignore native histograms in `scalar()`, `sort()` and `sort_desc()`. #15964
* [BUGFIX] PromQL: Fix annotations for binary operations between incompatible native histograms. #15895
* [BUGFIX] Alerting: Consider alert relabeling when deciding whether alerts are dropped. #15979
* [BUGFIX] Config: Set `GoGC` to the default value in case of an empty configuration. #16052
* [BUGFIX] TSDB: Fix unknown series errors and potential data loss during WAL replay when inactive series are removed from the head and reappear before the next WAL checkpoint. #16060
* [BUGFIX] Scaleway SD: The public IP will no longer be set to `__meta_meta_scaleway_instance_public_ipv4` if it is an IPv6 address. #14228
* [BUGFIX] UI: Display the correct value of Alerting rules' `keep_firing_for`. #16211

## 3.2.1 / 2025-02-25

* [BUGFIX] Don't send Accept` header `escape=allow-utf-8` when `metric_name_validation_scheme: legacy` is configured. #16061

## 3.2.0 / 2025-02-17

* [CHANGE] relabel: Replace actions can now use UTF-8 characters in `targetLabel` field. Note that `$<chars>` or `${<chars>}` will be expanded. This also apply to `replacement` field for `LabelMap` action. #15851
* [CHANGE] rulefmt: Rule names can use UTF-8 characters, except `{` and `}` characters (due to common mistake checks). #15851
* [FEATURE] remote/otlp: Add feature flag `otlp-deltatocumulative` to support conversion from delta to cumulative. #15165
* [ENHANCEMENT] openstack SD: Discover Octavia loadbalancers. #15539
* [ENHANCEMENT] scrape: Add metadata for automatic metrics to WAL for `metadata-wal-records` feature. #15837
* [ENHANCEMENT] promtool: Support linting of scrape interval, through lint option `too-long-scrape-interval`. #15719
* [ENHANCEMENT] promtool: Add --ignore-unknown-fields option. #15706
* [ENHANCEMENT] ui: Make "hide empty rules" and hide empty rules" persistent #15807
* [ENHANCEMENT] web/api: Add a limit parameter to `/query` and `/query_range`. #15552
* [ENHANCEMENT] api: Add fields Node and ServerTime to `/status`. #15784
* [PERF] Scraping: defer computing labels for dropped targets until they are needed by the UI.  #15261
* [BUGFIX] remotewrite2: Fix invalid metadata bug for metrics without metadata. #15829
* [BUGFIX] remotewrite2: Fix the unit field propagation. #15825
* [BUGFIX] scrape: Fix WAL metadata for histograms and summaries. #15832
* [BUGFIX] ui: Merge duplicate "Alerts page settings" sections. #15810
* [BUGFIX] PromQL: Fix `<aggr_over_time>` functions with histograms. #15711

## 3.1.0 / 2025-01-02

 * [SECURITY] upgrade golang.org/x/crypto to address reported CVE-2024-45337. #15691
 * [CHANGE] Notifier: Increment prometheus_notifications_errors_total by the number of affected alerts rather than per batch. #15428
 * [CHANGE] API: list rules field "groupNextToken:omitempty" renamed to "groupNextToken". #15400
 * [ENHANCEMENT] OTLP translate: keep identifying attributes in target_info. #15448
 * [ENHANCEMENT] Paginate rule groups, add infinite scroll to rules within groups. #15677
 * [ENHANCEMENT] TSDB: Improve calculation of space used by labels. #13880
 * [ENHANCEMENT] Rules: new metric rule_group_last_rule_duration_sum_seconds. #15672
 * [ENHANCEMENT] Observability: Export 'go_sync_mutex_wait_total_seconds_total' metric. #15339
 * [ENHANCEMEN] Remote-Write: optionally use a DNS resolver that picks a random IP. #15329
 * [PERF] Optimize `l=~".+"` matcher. #15474, #15684
 * [PERF] TSDB: Cache all symbols for compaction . #15455
 * [PERF] TSDB: MemPostings: keep a map of label values slices. #15426
 * [PERF] Remote-Write: Remove interning hook. #15456
 * [PERF] Scrape: optimize string manipulation for experimental native histograms with custom buckets. #15453
 * [PERF] TSDB: reduce memory allocations. #15465, #15427
 * [PERF] Storage: Implement limit in mergeGenericQuerier. #14489
 * [PERF] TSDB: Optimize inverse matching. #14144
 * [PERF] Regex: use stack memory for lowercase copy of string. #15210
 * [PERF] TSDB: When deleting from postings index, pause to unlock and let readers read. #15242
 * [BUGFIX] Main: Avoid possible segfault at exit. (#15724)
 * [BUGFIX] Rules: Do not run rules concurrently if uncertain about dependencies. #15560
 * [BUGFIX] PromQL: Adds test for `absent`, `absent_over_time` and `deriv` func with histograms. #15667
 * [BUGFIX] PromQL: Fix various bugs related to quoting UTF-8 characters. #15531
 * [BUGFIX] Scrape: fix nil panic after scrape loop reload. #15563
 * [BUGFIX] Remote-write: fix panic on repeated log message. #15562
 * [BUGFIX] Scrape: reload would ignore always_scrape_classic_histograms and convert_classic_histograms_to_nhcb configs. #15489
 * [BUGFIX] TSDB: fix data corruption in experimental native histograms. #15482
 * [BUGFIX] PromQL: Ignore histograms in all time related functions. #15479
 * [BUGFIX] OTLP receiver: Convert metric metadata. #15416
 * [BUGFIX] PromQL: Fix `resets` function for histograms. #15527
 * [BUGFIX] PromQL: Fix behaviour of `changes()` for mix of histograms and floats. #15469
 * [BUGFIX] PromQL: Fix behaviour of some aggregations with histograms. #15432
 * [BUGFIX] allow quoted exemplar keys in openmetrics text format. #15260
 * [BUGFIX] TSDB: fixes for rare conditions when loading write-behind-log (WBL). #15380
 * [BUGFIX] `round()` function did not remove `__name__` label. #15250
 * [BUGFIX] Promtool: analyze block shows metric name with 0 cardinality. #15438
 * [BUGFIX] PromQL: Fix `count_values` for histograms. #15422
 * [BUGFIX] PromQL: fix issues with comparison binary operations with `bool` modifier and native histograms. #15413
 * [BUGFIX] PromQL: fix incorrect "native histogram ignored in aggregation" annotations. #15414
 * [BUGFIX] PromQL: Corrects the behaviour of some operator and aggregators with Native Histograms. #15245
 * [BUGFIX] TSDB: Always return unknown hint for first sample in non-gauge histogram chunk. #15343
 * [BUGFIX] PromQL: Clamp functions: Ignore any points with native histograms. #15169
 * [BUGFIX] TSDB: Fix race on stale values in headAppender. #15322
 * [BUGFIX] UI: Fix selector / series formatting for empty metric names. #15340
 * [BUGFIX] OTLP receiver: Allow colons in non-standard units. #15710

## 3.0.1 / 2024-11-28

The first bug fix release for Prometheus 3.

* [BUGFIX] Promql: Make subqueries left open. #15431
* [BUGFIX] Fix memory leak when query log is enabled. #15434
* [BUGFIX] Support utf8 names on /v1/label/:name/values endpoint. #15399

## 3.0.0 / 2024-11-14

This release includes new features such as a brand new UI and UTF-8 support enabled by default. As this marks the first new major version in seven years, several breaking changes are introduced. The breaking changes are mainly around the removal of deprecated feature flags and CLI arguments, and the full list can be found below. For users that want to upgrade we recommend to read through our [migration guide](https://prometheus.io/docs/prometheus/3.0/migration/).

* [CHANGE] Set the `GOMAXPROCS` variable automatically to match the Linux CPU quota. Use `--no-auto-gomaxprocs` to disable it. The `auto-gomaxprocs` feature flag was removed. #15376
* [CHANGE] Set the `GOMEMLIMIT` variable automatically to match the Linux container memory limit. Use `--no-auto-gomemlimit` to disable it. The `auto-gomemlimit` feature flag was removed. #15373
* [CHANGE] Scraping: Remove implicit fallback to the Prometheus text format in case of invalid/missing Content-Type and fail the scrape instead. Add ability to specify a `fallback_scrape_protocol` in the scrape config. #15136
* [CHANGE] Remote-write: default enable_http2 to false. #15219
* [CHANGE] Scraping: normalize "le" and "quantile" label values upon ingestion. #15164
* [CHANGE] Scraping: config `scrape_classic_histograms` was renamed to `always_scrape_classic_histograms`. #15178
* [CHANGE] Config: remove expand-external-labels flag, expand external labels env vars by default. #14657
* [CHANGE] Disallow configuring AM with the v1 api. #13883
* [CHANGE] regexp `.` now matches all characters (performance improvement). #14505
* [CHANGE] `holt_winters` is now called `double_exponential_smoothing` and moves behind the [experimental-promql-functions feature flag](https://prometheus.io/docs/prometheus/latest/feature_flags/#experimental-promql-functions). #14930
* [CHANGE] API: The OTLP receiver endpoint can now be enabled using `--web.enable-otlp-receiver` instead of `--enable-feature=otlp-write-receiver`. #14894
* [CHANGE] Prometheus will not add or remove port numbers from the target address. `no-default-scrape-port` feature flag removed. #14160
* [CHANGE] Logging: the format of log lines has changed a little, along with the adoption of Go's Structured Logging package. #14906
* [CHANGE] Don't create extra `_created` timeseries if feature-flag `created-timestamp-zero-ingestion` is enabled. #14738
* [CHANGE] Float literals and time durations being the same is now a stable fetaure. #15111
* [CHANGE] UI: The old web UI has been replaced by a completely new one that is less cluttered and adds a few new features (PromLens-style tree view, better metrics explorer, "Explain" tab). However, it is still missing some features of the old UI (notably, exemplar display and heatmaps). To switch back to the old UI, you can use the feature flag `--enable-feature=old-ui` for the time being. #14872
* [CHANGE] PromQL: Range selectors and the lookback delta are now left-open, i.e. a sample coinciding with the lower time limit is excluded rather than included. #13904
* [CHANGE] Kubernetes SD: Remove support for `discovery.k8s.io/v1beta1` API version of EndpointSlice. This version is no longer served as of Kubernetes v1.25. #14365
* [CHANGE] Kubernetes SD: Remove support for `networking.k8s.io/v1beta1` API version of Ingress. This version is no longer served as of Kubernetes v1.22. #14365
* [CHANGE] UTF-8: Enable UTF-8 support by default. Prometheus now allows all UTF-8 characters in metric and label names. The corresponding `utf8-name` feature flag has been removed. #14705, #15258
* [CHANGE] Console: Remove example files for the console feature. Users can continue using the console feature by supplying their own JavaScript and templates. #14807
* [CHANGE] SD: Enable the new service discovery manager by default. This SD manager does not restart unchanged discoveries upon reloading. This makes reloads faster and reduces pressure on service discoveries' sources. The corresponding `new-service-discovery-manager` feature flag has been removed. #14770
* [CHANGE] Agent mode has been promoted to stable. The feature flag `agent` has been removed. To run Prometheus in Agent mode, use the new `--agent` cmdline arg instead. #14747
* [CHANGE] Remove deprecated `remote-write-receiver`,`promql-at-modifier`, and `promql-negative-offset` feature flags. #13456, #14526
* [CHANGE] Remove deprecated `storage.tsdb.allow-overlapping-blocks`, `alertmanager.timeout`, and `storage.tsdb.retention` flags. #14640, #14643
* [FEATURE] OTLP receiver: Ability to skip UTF-8 normalization using `otlp.translation_strategy = NoUTF8EscapingWithSuffixes` configuration option. #15384
* [FEATURE] Support config reload automatically - feature flag `auto-reload-config`. #14769, #15011
* [ENHANCEMENT] Scraping, rules: handle targets reappearing, or rules moving group, when out-of-order is enabled. #14710
* [ENHANCEMENT] Tools: add debug printouts to promtool rules unit testing #15196
* [ENHANCEMENT] Scraping: support Created-Timestamp feature on native histograms. #14694
* [ENHANCEMENT] UI: Many fixes and improvements. #14898, #14899, #14907, #14908, #14912, #14913, #14914, #14931, #14940, #14945, #14946, #14972, #14981, #14982, #14994, #15096
* [ENHANCEMENT] UI: Web UI now displays notifications, e.g. when starting up and shutting down. #15082
* [ENHANCEMENT] PromQL: Introduce exponential interpolation for native histograms. #14677
* [ENHANCEMENT] TSDB: Add support for ingestion of out-of-order native histogram samples. #14850, #14546
* [ENHANCEMENT] Alerts: remove metrics for removed Alertmanagers. #13909
* [ENHANCEMENT] Kubernetes SD: Support sidecar containers in endpoint discovery. #14929
* [ENHANCEMENT] Consul SD: Support catalog filters. #11224
* [ENHANCEMENT] Move AM discovery page from "Monitoring status" to "Server status". #14875
* [PERF] TSDB: Parallelize deletion of postings after head compaction. #14975
* [PERF] TSDB: Chunk encoding: shorten some write sequences. #14932
* [PERF] TSDB: Grow postings by doubling. #14721
* [PERF] Relabeling: Optimize adding a constant label pair. #12180
* [BUGFIX] Scraping: Don't log errors on empty scrapes. #15357
* [BUGFIX] UI: fix selector / series formatting for empty metric names. #15341
* [BUGFIX] PromQL: Fix stddev+stdvar aggregations to always ignore native histograms. #14941
* [BUGFIX] PromQL: Fix stddev+stdvar aggregations to treat Infinity consistently. #14941
* [BUGFIX] OTLP receiver: Preserve colons when generating metric names in suffix adding mode (this mode is always enabled, unless one uses Prometheus as a library). #15251
* [BUGFIX] Scraping: Unit was missing when using protobuf format. #15095
* [BUGFIX] PromQL: Only return "possible non-counter" annotation when `rate` returns points. #14910
* [BUGFIX] TSDB: Chunks could have one unnecessary zero byte at the end. #14854
* [BUGFIX] "superfluous response.WriteHeader call" messages in log. #14884
* [BUGFIX] PromQL: Unary negation of native histograms. #14821
* [BUGFIX] PromQL: Handle stale marker in native histogram series (e.g. if series goes away and comes back). #15025
* [BUGFIX] Autoreload: Reload invalid yaml files. #14947
* [BUGFIX] Scrape: Do not override target parameter labels with config params. #11029

## 2.53.5 / 2025-06-30

* [ENHANCEMENT] TSDB: Add backward compatibility with the upcoming TSDB block index v3 #16762
* [BUGFIX] Top-level: Update GOGC before loading TSDB #16521

## 2.53.4 / 2025-03-18

* [BUGFIX] Runtime: fix GOGC is being set to 0 when installed with empty prometheus.yml file resulting high cpu usage. #16090
* [BUGFIX] Scrape: fix dropping valid metrics after previous scrape failed. #16220

## 2.53.3 / 2024-11-04

* [BUGFIX] Scraping: allow multiple samples on same series, with explicit timestamps. #14685, #14740

## 2.53.2 / 2024-08-09

Fix a bug where Prometheus would crash with a segmentation fault if a remote-read
request accessed a block on disk at about the same time as TSDB created a new block.

* [BUGFIX] Remote-Read: Resolve occasional segmentation fault on query. #14515,#14523

## 2.55.1 / 2024-11-04

* [BUGFIX] `round()` function did not remove `__name__` label. #15250

## 2.55.0 / 2024-10-22

* [FEATURE] PromQL: Add experimental `info` function. #14495
* [FEATURE] Support UTF-8 characters in label names - feature flag `utf8-names`. #14482, #14880, #14736, #14727
* [FEATURE] Scraping: Add the ability to set custom `http_headers` in config. #14817
* [FEATURE] Scraping: Support feature flag `created-timestamp-zero-ingestion` in OpenMetrics. #14356, #14815
* [FEATURE] Scraping: `scrape_failure_log_file` option to log failures to a file. #14734
* [FEATURE] OTLP receiver: Optional promotion of resource attributes to series labels. #14200
* [FEATURE] Remote-Write: Support Google Cloud Monitoring authorization. #14346
* [FEATURE] Promtool: `tsdb create-blocks` new option to add labels. #14403
* [FEATURE] Promtool: `promtool test` adds `--junit` flag to format results. #14506
* [FEATURE] TSDB: Add `delayed-compaction` feature flag, for people running many Prometheus to randomize timing. #12532
* [ENHANCEMENT] OTLP receiver: Warn on exponential histograms with zero count and non-zero sum. #14706
* [ENHANCEMENT] OTLP receiver: Interrupt translation on context cancellation/timeout. #14612
* [ENHANCEMENT] Remote Read client: Enable streaming remote read if the server supports it. #11379
* [ENHANCEMENT] Remote-Write: Don't reshard if we haven't successfully sent a sample since last update. #14450
* [ENHANCEMENT] PromQL: Delay deletion of `__name__` label to the end of the query evaluation. This is **experimental** and enabled under the feature-flag `promql-delayed-name-removal`. #14477
* [ENHANCEMENT] PromQL: Experimental `sort_by_label` and `sort_by_label_desc` sort by all labels when label is equal. #14655, #14985
* [ENHANCEMENT] PromQL: Clarify error message logged when Go runtime panic occurs during query evaluation. #14621
* [ENHANCEMENT] PromQL: Use Kahan summation for better accuracy in `avg` and `avg_over_time`. #14413
* [ENHANCEMENT] Tracing: Improve PromQL tracing, including showing the operation performed for aggregates, operators, and calls. #14816
* [ENHANCEMENT] API: Support multiple listening addresses. #14665
* [ENHANCEMENT] TSDB: Backward compatibility with upcoming index v3. #14934
* [PERF] TSDB: Query in-order and out-of-order series together. #14354, #14693, #14714, #14831, #14874, #14948, #15120
* [PERF] TSDB: Streamline reading of overlapping out-of-order head chunks. #14729
* [BUGFIX] PromQL: make sort_by_label stable. #14985
* [BUGFIX] SD: Fix dropping targets (with feature flag `new-service-discovery-manager`). #13147
* [BUGFIX] SD: Stop storing stale targets (with feature flag `new-service-discovery-manager`). #13622
* [BUGFIX] Scraping: exemplars could be dropped in protobuf scraping. #14810
* [BUGFIX] Remote-Write: fix metadata sending for experimental Remote-Write V2. #14766
* [BUGFIX] Remote-Write: Return 4xx not 5xx when timeseries has duplicate label. #14716
* [BUGFIX] Experimental Native Histograms: many fixes for incorrect results, panics, warnings. #14513, #14575, #14598, #14609, #14611, #14771, #14821
* [BUGFIX] TSDB: Only count unknown record types in `record_decode_failures_total` metric. #14042

## 2.54.1 / 2024-08-27

* [BUGFIX] Scraping: allow multiple samples on same series, with explicit timestamps (mixing samples of the same series with and without timestamps is still rejected). #14685
* [BUGFIX] Docker SD: fix crash in `match_first_network` mode when container is reconnected to a new network. #14654
* [BUGFIX] PromQL: fix experimental native histograms getting corrupted due to vector selector bug in range queries. #14538
* [BUGFIX] PromQL: fix experimental native histogram counter reset detection on stale samples. #14514
* [BUGFIX] PromQL: fix native histograms getting corrupted due to vector selector bug in range queries. #14605

## 2.54.0 / 2024-08-09

Release 2.54 brings a release candidate of a major new version of [Remote Write: 2.0](https://prometheus.io/docs/specs/remote_write_spec_2_0/).
This is experimental at this time and may still change.
Remote-write v2 is enabled by default, but can be disabled via feature-flag `web.remote-write-receiver.accepted-protobuf-messages`.

* [CHANGE] Remote-Write: `highest_timestamp_in_seconds` and `queue_highest_sent_timestamp_seconds` metrics now initialized to 0. #14437
* [CHANGE] API: Split warnings from info annotations in API response. #14327
* [FEATURE] Remote-Write: Version 2.0 experimental, plus metadata in WAL via feature flag `metadata-wal-records` (defaults on). #14395,#14427,#14444
* [FEATURE] PromQL: add limitk() and limit_ratio() aggregation operators. #12503
* [ENHANCEMENT] PromQL: Accept underscores in literal numbers, e.g. 1_000_000 for 1 million. #12821
* [ENHANCEMENT] PromQL: float literal numbers and durations are now interchangeable (experimental). Example: `time() - my_timestamp > 10m`. #9138
* [ENHANCEMENT] PromQL: use Kahan summation for sum(). #14074,#14362
* [ENHANCEMENT] PromQL (experimental native histograms): Optimize `histogram_count` and `histogram_sum` functions. #14097
* [ENHANCEMENT] TSDB: Better support for out-of-order experimental native histogram samples. #14438
* [ENHANCEMENT] TSDB: Optimise seek within index. #14393
* [ENHANCEMENT] TSDB: Optimise deletion of stale series. #14307
* [ENHANCEMENT] TSDB: Reduce locking to optimise adding and removing series. #13286,#14286
* [ENHANCEMENT] TSDB: Small optimisation: streamline special handling for out-of-order data. #14396,#14584
* [ENHANCEMENT] Regexps: Optimize patterns with multiple prefixes. #13843,#14368
* [ENHANCEMENT] Regexps: Optimize patterns containing multiple literal strings. #14173
* [ENHANCEMENT] AWS SD: expose Primary IPv6 addresses as __meta_ec2_primary_ipv6_addresses. #14156
* [ENHANCEMENT] Docker SD: add MatchFirstNetwork for containers with multiple networks. #10490
* [ENHANCEMENT] OpenStack SD: Use `flavor.original_name` if available. #14312
* [ENHANCEMENT] UI (experimental native histograms): more accurate representation. #13680,#14430
* [ENHANCEMENT] Agent: `out_of_order_time_window` config option now applies to agent. #14094
* [ENHANCEMENT] Notifier: Send any outstanding Alertmanager notifications when shutting down. #14290
* [ENHANCEMENT] Rules: Add label-matcher support to Rules API. #10194
* [ENHANCEMENT] HTTP API: Add url to message logged on error while sending response. #14209
* [BUGFIX] TSDB: Exclude OOO chunks mapped after compaction starts (introduced by #14396). #14584
* [BUGFIX] CLI: escape `|` characters when generating docs. #14420
* [BUGFIX] PromQL (experimental native histograms): Fix some binary operators between native histogram values. #14454
* [BUGFIX] TSDB: LabelNames API could fail during compaction. #14279
* [BUGFIX] TSDB: Fix rare issue where pending OOO read can be left dangling if creating querier fails. #14341
* [BUGFIX] TSDB: fix check for context cancellation in LabelNamesFor. #14302
* [BUGFIX] Rules: Fix rare panic on reload. #14366
* [BUGFIX] Config: In YAML marshalling, do not output a regexp field if it was never set. #14004
* [BUGFIX] Remote-Write: reject samples with future timestamps. #14304
* [BUGFIX] Remote-Write: Fix data corruption in remote write if max_sample_age is applied. #14078
* [BUGFIX] Notifier: Fix Alertmanager discovery not updating under heavy load. #14174
* [BUGFIX] Regexes: some Unicode characters were not matched by case-insensitive comparison. #14170,#14299
* [BUGFIX] Remote-Read: Resolve occasional segmentation fault on query. #14515

## 2.53.1 / 2024-07-10

Fix a bug which would drop samples in remote-write if the sending flow stalled
for longer than it takes to write one "WAL segment". How long this takes depends on the size
of your Prometheus; as a rough guide with 10 million series it is about 2-3 minutes.

* [BUGFIX] Remote-write: stop dropping samples in catch-up #14446

## 2.53.0 / 2024-06-16

This release changes the default for GOGC, the Go runtime control for the trade-off between excess memory use and CPU usage. We have found that Prometheus operates with minimal additional CPU usage, but greatly reduced memory by adjusting the upstream Go default from 100 to 75.

* [CHANGE] Rules: Execute 1 query instead of N (where N is the number of alerts within alert rule) when restoring alerts. #13980 #14048
* [CHANGE] Runtime: Change GOGC threshold from 100 to 75 #14176 #14285
* [FEATURE] Rules: Add new option `query_offset` for each rule group via rule group configuration file and `rule_query_offset` as part of the global configuration to have more resilience for remote write delays. #14061 #14216 #14273
* [ENHANCEMENT] Rules: Add `rule_group_last_restore_duration_seconds` metric to measure the time it takes to restore a rule group. #13974
* [ENHANCEMENT] OTLP: Improve remote write format translation performance by using label set hashes for metric identifiers instead of string based ones. #14006 #13991
* [ENHANCEMENT] TSDB: Optimize querying with regexp matchers. #13620
* [BUGFIX] OTLP: Don't generate target_info unless there are metrics and at least one identifying label is defined. #13991
* [BUGFIX] Scrape: Do no try to ingest native histograms when the native histograms feature is turned off. This happened when protobuf scrape was enabled by for example the created time feature. #13987
* [BUGFIX] Scaleway SD: Use the instance's public IP if no private IP is available as the `__address__` meta label. #13941
* [BUGFIX] Query logger: Do not leak file descriptors on error. #13948
* [BUGFIX] TSDB: Let queries with heavy regex matches be cancelled and not use up the CPU. #14096 #14103 #14118 #14199
* [BUGFIX] API: Do not warn if result count is equal to the limit, only when exceeding the limit for the series, label-names and label-values APIs. #14116
* [BUGFIX] TSDB: Fix head stats and hooks when replaying a corrupted snapshot. #14079

## 2.52.1 / 2024-05-29

* [BUGFIX] Linode SD: Fix partial fetch when discovery would return more than 500 elements. #14141

## 2.52.0 / 2024-05-07

* [CHANGE] TSDB: Fix the predicate checking for blocks which are beyond the retention period to include the ones right at the retention boundary. #9633
* [CHANGE] Scrape: Multiple samples (even with different timestamps) are treated as duplicates during one scrape.
* [FEATURE] Kubernetes SD: Add a new metric `prometheus_sd_kubernetes_failures_total` to track failed requests to Kubernetes API. #13554
* [FEATURE] Kubernetes SD: Add node and zone metadata labels when using the endpointslice role. #13935
* [FEATURE] Azure SD/Remote Write: Allow usage of Azure authorization SDK. #13099
* [FEATURE] Alerting: Support native histogram templating. #13731
* [FEATURE] Linode SD: Support IPv6 range discovery and region filtering. #13774
* [ENHANCEMENT] PromQL: Performance improvements for queries with regex matchers. #13461
* [ENHANCEMENT] PromQL: Performance improvements when using aggregation operators. #13744
* [ENHANCEMENT] PromQL: Validate label_join destination label. #13803
* [ENHANCEMENT] Scrape: Increment `prometheus_target_scrapes_sample_duplicate_timestamp_total` metric on duplicated series during one scrape. #12933
* [ENHANCEMENT] TSDB: Many improvements in performance. #13742 #13673 #13782
* [ENHANCEMENT] TSDB: Pause regular block compactions if the head needs to be compacted (prioritize head as it increases memory consumption). #13754
* [ENHANCEMENT] Observability: Improved logging during signal handling termination. #13772
* [ENHANCEMENT] Observability: All log lines for drop series use "num_dropped" key consistently. #13823
* [ENHANCEMENT] Observability: Log chunk snapshot and mmapped chunk replay duration during WAL replay. #13838
* [ENHANCEMENT] Observability: Log if the block is being created from WBL during compaction. #13846
* [BUGFIX] PromQL: Fix inaccurate sample number statistic when querying histograms. #13667
* [BUGFIX] PromQL: Fix `histogram_stddev` and `histogram_stdvar` for cases where the histogram has negative buckets. #13852
* [BUGFIX] PromQL: Fix possible duplicated label name and values in a metric result for specific queries. #13845
* [BUGFIX] Scrape: Fix setting native histogram schema factor during scrape. #13846
* [BUGFIX] TSDB: Fix counting of histogram samples when creating WAL checkpoint stats. #13776
* [BUGFIX] TSDB: Fix cases of compacting empty heads. #13755
* [BUGFIX] TSDB: Count float histograms in WAL checkpoint. #13844
* [BUGFIX] Remote Read: Fix memory leak due to broken requests. #13777
* [BUGFIX] API: Stop building response for `/api/v1/series/` when the API request was cancelled. #13766
* [BUGFIX] promtool: Fix panic on `promtool tsdb analyze --extended` when no native histograms are present. #13976

## 2.51.2 / 2024-04-09

Bugfix release.

[BUGFIX] Notifier: could hang when using relabeling on alerts #13861

## 2.51.1 / 2024-03-27

Bugfix release.

* [BUGFIX] PromQL: Re-instate validation of label_join destination label #13803
* [BUGFIX] Scraping (experimental native histograms): Fix handling of the min bucket factor on sync of targets #13846
* [BUGFIX] PromQL: Some queries could return the same series twice (library use only) #13845

## 2.51.0 / 2024-03-18

This version is built with Go 1.22.1.

There is a new optional build tag "dedupelabels", which should reduce memory consumption (#12304).
It is off by default; there will be an optional alternative image to try it out.

* [CHANGE] Scraping: Do experimental timestamp alignment even if tolerance is bigger than 1% of scrape interval #13624, #13737
* [FEATURE] Alerting: Relabel rules for AlertManagerConfig; allows routing alerts to different alertmanagers #12551, #13735
* [FEATURE] API: add limit param to series, label-names and label-values APIs #13396
* [FEATURE] UI (experimental native histograms): Add native histogram chart to Table view #13658
* [FEATURE] Promtool: Add a "tsdb dump-openmetrics" to dump in OpenMetrics format. #13194
* [FEATURE] PromQL (experimental native histograms): Add histogram_avg function #13467
* [ENHANCEMENT] Rules: Evaluate independent rules concurrently #12946, #13527
* [ENHANCEMENT] Scraping (experimental native histograms): Support exemplars #13488
* [ENHANCEMENT] Remote Write: Disable resharding during active retry backoffs #13562
* [ENHANCEMENT] Observability: Add native histograms to latency/duration metrics #13681
* [ENHANCEMENT] Observability: Add 'type' label to prometheus_tsdb_head_out_of_order_samples_appended_total #13607
* [ENHANCEMENT] API: Faster generation of targets into JSON #13469, #13484
* [ENHANCEMENT] Scraping, API: Use faster compression library #10782
* [ENHANCEMENT] OpenTelemetry: Performance improvements in OTLP parsing #13627
* [ENHANCEMENT] PromQL: Optimisations to reduce CPU and memory #13448, #13536
* [BUGFIX] PromQL: Constrain extrapolation in rate() to half of sample interval #13725
* [BUGFIX] Remote Write: Stop slowing down when a new WAL segment is created #13583, #13628
* [BUGFIX] PromQL: Fix wrongly scoped range vectors with @ modifier #13559
* [BUGFIX] Kubernetes SD: Pod status changes were not discovered by Endpoints service discovery #13337
* [BUGFIX] Azure SD: Fix 'error: parameter virtualMachineScaleSetName cannot be empty' (#13702)
* [BUGFIX] Remote Write: Fix signing for AWS sigv4 transport #13497
* [BUGFIX] Observability: Exemplars emitted by Prometheus use "trace_id" not "traceID" #13589

## 2.50.1 / 2024-02-26

* [BUGFIX] API: Fix metadata API using wrong field names. #13633

## 2.50.0 / 2024-02-22

* [CHANGE] Remote Write: Error `storage.ErrTooOldSample` is now generating HTTP error 400 instead of HTTP error 500. #13335
* [FEATURE] Remote Write: Drop old inmemory samples. Activated using the config entry `sample_age_limit`. #13002
* [FEATURE] **Experimental**: Add support for ingesting zeros as created timestamps. (enabled under the feature-flag `created-timestamp-zero-ingestion`). #12733 #13279
* [FEATURE] Promtool: Add `analyze` histograms command. #12331
* [FEATURE] TSDB/compaction: Add a way to enable overlapping compaction. #13282 #13393 #13398
* [FEATURE] Add automatic