Update Prometheus and Loki by thampiotr · Pull Request #5035 · grafana/alloy

thampiotr · 2025-12-09T11:23:44Z

PR Description

This finally gets rid of our Prometheus fork.
Not all new experimental features in Prometheus are exposed. Instead there are some TODOs left in the code to GH issues which should address this. This is to keep the PR smaller and prioritise the work accordingly.

Which issue(s) this PR fixes

Notes to the Reviewer

PR Checklist

CHANGELOG.md updated
Documentation added
Tests updated
Config converters updated

internal/component/prometheus/operator/common/crdmanager.go

internal/component/prometheus/receive_http/receive_http.go

internal/component/prometheus/scrape/scrape.go

go.mod

thampiotr · 2025-12-09T13:31:01Z

internal/component/prometheus/scrape/scrape.go

 	dec.HonorTimestamps = c.HonorTimestamps
 	dec.TrackTimestampsStaleness = c.TrackTimestampsStaleness
 	dec.Params = c.Params
+	dec.ScrapeNativeHistograms = &copyScrapeNativeHistograms


This setting is now per-scrape-job, moved from manager-wide setting above.

github-actions · 2025-12-09T13:55:01Z

💻 Deploy preview deleted (Update Prometheus and Loki).

Copilot

Pull request overview

This PR updates Prometheus dependencies to v3.8.0 (module version v0.308.0) and Loki dependencies to v3.6.2, representing a significant upgrade to the latest versions of these core components. The changes primarily involve migrating to new Prometheus API patterns and updating import paths for remote write functionality.

Key Changes

Migrated from config.RemoteWriteProtoMsg to remote.WriteMessageType for remote write protocol types, importing from github.com/prometheus/client_golang/exp/api/remote instead of github.com/prometheus/prometheus/config
Removed EnableNativeHistogramsIngestion from scrape.Options in favor of setting ScrapeNativeHistograms directly in scrape configurations
Added TODO comments with GitHub issue links for new experimental Prometheus features (EnableCreatedTimestampZeroIngestion, EnableTypeAndUnitLabels, appendMetadata) that are not yet exposed in Alloy components

Reviewed changes

Copilot reviewed 8 out of 9 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
`internal/component/prometheus/write/queue/types.go`	Updated imports and type references from `config.RemoteWriteProtoMsg` to `remote.WriteMessageType`
`internal/component/prometheus/scrape/scrape.go`	Removed `EnableNativeHistogramsIngestion` from scrape options, added `ScrapeNativeHistograms` to scrape config, added TODOs for new experimental features
`internal/component/prometheus/remotewrite/types.go`	Updated remote write protocol type imports and usage
`internal/component/prometheus/receive_http/receive_http.go`	Updated handler initialization with new parameters, added TODO comments for unexposed features, aliased prometheus/storage/remote import to avoid conflicts
`internal/component/prometheus/operator/common/crdmanager.go`	Simplified scrape manager creation with empty options, added TODOs for experimental features
`go.sum`	Updated dependency hashes for Prometheus v0.308.0, Loki v3.6.2, and related AWS SDK, DigitalOcean, Docker, Hetzner, Linode, and etcd dependencies
`go.mod`	Updated Prometheus to v0.308.0, Loki to v3.6.2, and consolidated dependency declarations
`docs/sources/shared/reference/components/prom-operator-scrape.md`	Clarified `scrape_native_histograms` documentation from "ingest native histograms" to "scrape native histograms from targets"
`CHANGELOG.md`	Added entries documenting Prometheus v3.8.0 and Loki v3.6.2 updates

github-actions · 2025-12-10T14:07:18Z

🔍 Dependency Review

Below is a review of the dependency changes in go.mod, what changed upstream between the “as-is” and “to-be” versions, and the concrete code updates needed to adopt them. For each dependency you’ll find a status and collapsible details with evidence and example diffs.

Note: The largest change here is moving Prometheus to v3.8.0 (module tag v0.308.0) and dropping the fork/replace directives. That upgrade includes several breaking API changes that this PR already addresses.

github.com/prometheus/prometheus v0.305.1-0.20250818080900-0a40df33fb4e (with grafana fork replace) -> v0.308.0 — ❌ Changes Needed

Status: Breaking changes required code updates. This PR implements them. Below is a summary of what changed and the exact code updates needed (with evidence).

Key upstream changes relevant between v3.6.x → v3.8.0:

Remote write “protobuf message” types moved to client_golang/exp (not in prometheus/config anymore).
remote.WriteHandler signature extended (new enableTypeAndUnitLabels, appendMetadata).
ScrapeManager options: EnableNativeHistogramsIngestion moved out of scrape.Options into per-scrape config (ScrapeConfig.ScrapeNativeHistograms pointer).
Additional toggles added (AppendMetadata, EnableTypeAndUnitLabels, EnableCreatedTimestampZeroIngestion).
Some label constants usage was standardized via prometheus/common/model (e.g., MetricNameLabel).

Evidence in this PR:

Imports switched from “prometheus/config” message types to “client_golang/exp/api/remote”.
remote write handler construction updated to new signature.
scrape.Options no longer uses EnableNativeHistogramsIngestion; per-scrape configs now set ScrapeNativeHistograms pointer.
Tests updated to set ScrapeNativeHistograms as a pointer and to expect it in rendered configs.
Places that constructed metric name labels were updated to use model.MetricNameLabel.

Concrete code updates to apply (already in this PR):

Remote write message type constants moved:

Before:

- import "github.com/prometheus/prometheus/config"
+ import "github.com/prometheus/client_golang/exp/api/remote"

- PrometheusProtobufMessageV1 = string(config.RemoteWriteProtoMsgV1)
- PrometheusProtobufMessageV2 = string(config.RemoteWriteProtoMsgV2)
+ PrometheusProtobufMessageV1 = string(remote.WriteV1MessageType)
+ PrometheusProtobufMessageV2 = string(remote.WriteV2MessageType)

- if err := config.RemoteWriteProtoMsg(r.ProtobufMessage).Validate(); err != nil {
+ if err := remote.WriteMessageType(r.ProtobufMessage).Validate(); err != nil {
     ...
  }

NewWriteHandler signature:

Before:

- import "github.com/prometheus/prometheus/storage/remote"
- import "github.com/prometheus/prometheus/config"

- supportedRemoteWriteProtoMsgs := config.RemoteWriteProtoMsgs{config.RemoteWriteProtoMsgV1}
- ingestCTZeroSample := false

- handler: remote.NewWriteHandler(
+ import (
+   expremote "github.com/prometheus/client_golang/exp/api/remote"
+   promremote "github.com/prometheus/prometheus/storage/remote"
+ )

+ supportedRemoteWriteProtoMsgs := expremote.MessageTypes{expremote.WriteV1MessageType}
+ ingestCTZeroSample := false
+ enableTypeAndUnitLabels := false
+ appendMetadata := false

+ handler: promremote.NewWriteHandler(
     logger,
     reg,
     fanout,
     supportedRemoteWriteProtoMsgs,
-    ingestCTZeroSample,
+    ingestCTZeroSample,
+    enableTypeAndUnitLabels,
+    appendMetadata,
   ),

ScrapeManager Options and per-scrape native histograms:

Before (EnableNativeHistogramsIngestion lived in scrape.Options):

- opts := &scrape.Options{
-   EnableNativeHistogramsIngestion: c.args.Scrape.ScrapeNativeHistograms,
- }
- c.scrapeManager, err = scrape.NewManager(opts, logger, nil, app, unregisterer)
+ // Now native histograms are controlled per-target in ScrapeConfig (ScrapeNativeHistograms).
+ c.scrapeManager, err = scrape.NewManager(&scrape.Options{}, logger, nil, app, unregisterer)

Set per-scrape in decoders/builders (pointer):

+ copyScrapeNativeHistograms := c.ScrapeNativeHistograms
+ dec.ScrapeNativeHistograms = &copyScrapeNativeHistograms

Tests updated to expect pointer:

+ ScrapeNativeHistograms:         falsePtr,

Forwarded config conversion for remote write protobuf message:

Before:

- ProtobufMessage: config.RemoteWriteProtoMsg(rw.ProtobufMessage),
+ ProtobufMessage: remote.WriteMessageType(rw.ProtobufMessage),

Label name constant usage (metric name):

Before:

- import "github.com/prometheus/prometheus/model/labels"
+ import "github.com/prometheus/common/model"

- builder.Add(labels.MetricName, metric)
+ builder.Add(model.MetricNameLabel, metric)

Write queue types wrapper for protobuf message moved:

Before:

- type RemoteWriteProtoMsg config.RemoteWriteProtoMsg
+ type RemoteWriteProtoMsg remote.WriteMessageType

- case string(config.RemoteWriteProtoMsgV1):
-   *s = RemoteWriteProtoMsg(config.RemoteWriteProtoMsgV1)
+ case string(remote.WriteV1MessageType):
+   *s = RemoteWriteProtoMsg(remote.WriteV1MessageType)

Additional knobs introduced upstream you may want to expose later (captured and TODO’d in code):

EnableCreatedTimestampZeroIngestion
EnableTypeAndUnitLabels
AppendMetadata

References (relevant upstream changes):

Prometheus v3.8.0 release and PRs: Remote write handler and exp API migration; scrape native histograms configuration moved per-target.
Removal of fork/replace: replace github.com/prometheus/prometheus => github.com/grafana/prometheus (…) is now gone; upstream is usable at v0.308.0.

github.com/prometheus/client_golang/exp (new) -> v0.0.0-20250914183048-a974e0d45e0a — ⚠️ Needs Review

Status: Introduced as a new direct dependency. Required for the new experimental remote write API types used by Prometheus v3.8.0.

What changed / how to use:

Remote write “protobuf message” enums/types now live under:
- github.com/prometheus/client_golang/exp/api/remote
- Types: WriteV1MessageType, WriteV2MessageType, MessageTypes and Validate() helpers.

Example updates (already in this PR):

- import "github.com/prometheus/prometheus/config"
+ import "github.com/prometheus/client_golang/exp/api/remote"

- PrometheusProtobufMessageV1 = string(config.RemoteWriteProtoMsgV1)
- PrometheusProtobufMessageV2 = string(config.RemoteWriteProtoMsgV2)
+ PrometheusProtobufMessageV1 = string(remote.WriteV1MessageType)
+ PrometheusProtobufMessageV2 = string(remote.WriteV2MessageType)

- if err := config.RemoteWriteProtoMsg(r.ProtobufMessage).Validate(); err != nil {
+ if err := remote.WriteMessageType(r.ProtobufMessage).Validate(); err != nil {
    ...
 }

Use this exp module only where necessary (remote write msg types). No additional code changes required beyond the import and type swaps shown above.

github.com/prometheus/common v0.67.1 -> v0.67.4 — ✅ Safe

Status: Patch-level update with bug fixes and small improvements. No breaking changes detected.

Note:

You’ve standardized on github.com/prometheus/common/model.MetricNameLabel in a few places (good practice), but this change wasn’t strictly required by this bump.

No project code changes required beyond what’s already done.

github.com/prometheus/sigv4 v0.2.1 -> v0.3.0 — ✅ Safe

Status: Minor release. No breaking changes affecting your usage via prometheus/prometheus/config’s SigV4Config were found. Existing config mapping continues to work.