[amazon-cloudwatch-agent-operator] Route SM/PM by cloudwatch.aws/scraper annotation by wenegiemepraise · Pull Request #399 · aws/amazon-cloudwatch-agent-operator

wenegiemepraise · 2026-07-15T11:34:43Z

Summary

Route ServiceMonitor/PodMonitor discovery across CloudWatch agents by the
cloudwatch.aws/scraper annotation on the monitor CR. A monitor annotated
cloudwatch.aws/scraper: cluster-scraper is scraped only by the cluster-scraper agent's Target
Allocator; all others only by the per-node agent's.

What

New spec.targetAllocator.prometheusCR.scraperRole field (Target Allocator config scraper_role).
Client-side annotation filter in the TA watcher (annotationRoleMatches) applied during monitor
discovery in LoadConfig. cluster-scraper role keeps only annotated monitors; the empty
(default) role keeps only unannotated ones — complementary, so every monitor is owned by exactly
one agent (no double-scrape, no gap).

Why annotation (not label)

The routing key is behavioural config, not identity. Both agents' TAs already list all monitors
into their cache and filter client-side, and the two roles' selections union to the full set — so
server-side label filtering would gain nothing here. Filtering by annotation is a few lines in the
existing ListAll callback.

Testing

go build ./... and unit tests pass, incl. new TestAnnotationRoleMatches (8 cases + partition invariant).
Live-verified end to end on an EKS cluster: an annotated PodMonitor appeared only in the
cluster-scraper TA /jobs; an unannotated one only in the per-node TA /jobs.
Local build uses GOPROXY=direct GOSUMDB=off (offline proxy); CI is the authoritative gate.

Dependencies / stacking

Stacks on the per-node allocation operator work (#398, ta-per-node-allocation). Companion helm PR:
[amazon-cloudwatch-observability] Route SM/PM to cluster-scraper by annotation.

musa-asad · 2026-07-21T15:43:22Z

+	// not so annotated. This lets a heavy/singleton monitor be routed to the central cluster-scraper
+	// agent while all others stay on the per-node agent.
+	// +optional
+	ScraperRole string `json:"scraperRole,omitempty"`


scraperRole has no enum validation, so a typo like cluster-scaper quietly falls back to the default role and that monitor gets scraped by nobody. The chart hardcodes the right value today, but could we add +kubebuilder:validation:Enum=cluster-scraper and regenerate the CRD?

musa-asad · 2026-07-21T15:43:23Z

+	if !annotationRoleMatches(w.scraperRole, annotations) {
+		return false
+	}
+	if w.scraperRole == clusterScraperRole {


selectsMonitor logs an Info line for every monitor the cluster-scraper claims, and LoadConfig reruns on each reconcile, so a big annotated set means a lot of repeated lines. Low risk, but could we log only on membership change or drop it to V(1)?

musa-asad · 2026-07-21T15:43:24Z

+// TestLoadConfigScraperRouting exercises the annotation filter through the real LoadConfig path
+// (matching TestLoadConfig's harness): an annotated ServiceMonitor is discovered by the
+// cluster-scraper role and excluded by the default role.
+func TestLoadConfigScraperRouting(t *testing.T) {


The unannotated and PodMonitor cases never actually go through LoadConfig even though PodMonitor discovery mirrors ServiceMonitor, and the informer wait is a HasSynced spin loop with no deadline that hangs until CI kills it. Could we add both LoadConfig cases and use cache.WaitForCacheSync with a timeout?

musa-asad · 2026-07-21T15:43:25Z

+// Allocator, based on its scraperRole. cluster-scraper role selects only monitors annotated
+// cloudwatch.aws/scraper: cluster-scraper; the default role (empty) selects only monitors that are
+// not so annotated, so the two roles partition monitors with no overlap and no gap.
+func annotationRoleMatches(scraperRole string, annotations map[string]string) bool {


Routing is binary here (only cluster-scraper routes, everything else falls to per-node), so a future gpu-scraper would silently land on per-node. Could we add a note that annotationRoleMatches needs to become an explicit role to value match before a third role shows up?

musa-asad · 2026-07-21T15:43:26Z

 	}

+	if len(params.OtelCol.Spec.TargetAllocator.PrometheusCR.ScraperRole) > 0 {
+		taConfig["scraper_role"] = params.OtelCol.Spec.TargetAllocator.PrometheusCR.ScraperRole


The operator writes the scraper_role key, which an older Target Allocator image rejects as unknown and then CrashLoopBackOffs on, taking the cluster-scraper path down. Could we make sure the chart pins the operator and Target Allocator images from this commit or newer together?

Aakash-Dantre · 2026-09-23T10:58:20Z

Checklist posted for the PR author to move into the PR description under a ## PR Checklist heading.

PR Checklist

Commits are squashed into a logical, reviewable set — one commit for this PR's own work; the three inherited commits belong to the unmerged Fix Target Allocator startup crashes, PrometheusCR watcher, and Prometheus config pod restart #386 and are left attributed to their author
Commits and PR description comply with Amazon internal guidelines
make passes locally — go build ./... clean, make manifests idempotent (CRD regenerated), make impi and make checklicense pass, unit tests pass
All GitHub Actions checks on the PR are passing
Integration test evidence: link to a passing run, or state N/A with the reason
New or updated integration test coverage: [amazon-cloudwatch-agent-test] Add scraper routing integration tests amazon-cloudwatch-agent-test#724 (scraper_routing_test.go)
New functionality has unit tests; bug fixes have a reproducing test
Config translation changes include updated golden files — N/A, no translator changes
Breaking or customer-visible changes are called out in the PR description

Note for the description: scraperRole is constrained by +kubebuilder:validation:Enum=cluster-scraper
with no empty member, so the default (per-node) role can only be expressed by omitting the field —
setting scraperRole: "" explicitly is rejected by the API server. Worth documenting, or widening
the enum to include "".

Routes a ServiceMonitor/PodMonitor to the central cluster-scraper agent via the cloudwatch.aws/scraper: cluster-scraper annotation on the monitor CR. The cluster-scraper gets its own Target Allocator and prometheusCR with scraperRole: cluster-scraper and consistent-hashing allocation; the per-node agent keeps the default (empty) role and per-node allocation. The Target Allocator ClusterRole/ClusterRoleBinding render once (all Target Allocators share the target-allocator-service-acct service account), so a second Target-Allocator-bearing agent no longer produces a duplicate-named object. The bundled CRD's scraperRole field carries the enum: [cluster-scraper] constraint generated by the operator. Companion: aws/amazon-cloudwatch-agent-operator#399.

…er startup The target-allocator declared the enable-prometheus-cr-watcher flag name as a constant but never registered it on the flag set, while the operator passes --enable-prometheus-cr-watcher whenever PrometheusCR.enabled is true. Because args are parsed with pflag.ExitOnError, the unregistered flag caused the binary to print 'unknown flag' and exit(2), putting the target-allocator pod into CrashLoopBackOff. This change registers the flag and ORs it with the YAML prometheus_cr.enabled setting, then fixes three latent defects that were previously unreachable because the binary crashed first: - promOperator: set a non-empty Namespace on the synthetic Prometheus object so the prometheus-operator config generator no longer panics with 'namespace can't be empty' in store.ForNamespace. - promOperator: set EvaluationInterval so the generated config does not render an empty global.evaluation_interval, which the prometheus config parser rejects with 'empty duration string'. - main: create and register service-discovery metrics and pass them to discovery.NewManager; passing a nil sdMetrics map makes every SD provider fail to register, yielding zero discovered targets. RELEASE_NOTES updated. (cherry picked from commit 1376451)

Add a regression test asserting that loading a Target Allocator config whose static scrape job omits scrape_protocols still yields a non-empty ScrapeProtocols on every loaded scrape config. This is defaulted by the pinned Prometheus library during yaml.UnmarshalStrict into the prometheus Config type, so the distributed /scrape_configs payload is never empty and the agent's prometheus-receiver validation passes. The test fails fast if a future dependency or load-path change drops this defaulting. (cherry picked from commit 0405f4d)

The pod-template restart-trigger sha256 was computed from Spec.Config only, so a change to Spec.Prometheus (rendered into a separate ConfigMap) left the pod template byte-identical and the workload controller did not roll the pods. Fold the serialized Spec.Prometheus (PrometheusConfig.Yaml()) into the hash input when it is non-empty, so a Prometheus-only change bumps the pod-template annotation and triggers a rolling restart, matching agent-config behavior. When no Prometheus config is set the hash input is byte-identical to the agent config alone, leaving non-Prometheus agents unaffected. (cherry picked from commit d61d693)

Adds a per-node allocation strategy so each CloudWatch Agent scrapes only the ServiceMonitor/PodMonitor targets on its own node, eliminating cross-node and cross-AZ scrape traffic. Targets with no resolvable node fall back to consistent-hashing so nothing is silently dropped, and unassigned targets are surfaced via a gauge. Also changes collector registration for ALL strategies, including the existing consistent-hashing default: the initial List now skips pods with an empty spec.NodeName, watch.Modified is handled so a pod scheduled after Add is picked up, and pods are dropped as soon as they carry a DeletionTimestamp rather than on Deleted. This releases a terminating agent's targets immediately instead of at the end of its grace period, at the cost of more target churn during rollouts. Verified: go build ./... clean; make impi and make checklicense pass; unit tests pass across the target-allocator and manifests packages. (cherry picked from commit 1595a87)

Partitions ServiceMonitor/PodMonitor discovery across CloudWatch Agents by the cloudwatch.aws/scraper annotation on the monitor CR. A monitor annotated cluster-scraper is scraped only by the cluster-scraper agent's Target Allocator; all others only by the per-node agent's. The two roles are complementary, so every monitor is owned by exactly one agent with no double-scrape and no gap. Adds spec.targetAllocator.prometheusCR.scraperRole (Target Allocator config key scraper_role) and a client-side annotation filter applied during monitor discovery in LoadConfig. Note: scraperRole is constrained by an enum with no empty member, so the default per-node role is expressed by omitting the field; setting scraperRole: "" explicitly is rejected by the API server. Companion: aws-observability/helm-charts#339. Verified: go build ./... clean; make impi and make checklicense pass; unit tests pass across the target-allocator and manifests packages. (cherry picked from commit cd3e40b)

Routes a ServiceMonitor/PodMonitor to the central cluster-scraper agent via the cloudwatch.aws/scraper: cluster-scraper annotation on the monitor CR. The cluster-scraper gets its own Target Allocator and prometheusCR with scraperRole: cluster-scraper and consistent-hashing allocation; the per-node agent keeps the default (empty) role and per-node allocation. The Target Allocator ClusterRole/ClusterRoleBinding render once (all Target Allocators share the target-allocator-service-acct service account), so a second Target-Allocator-bearing agent no longer produces a duplicate-named object. The bundled CRD's scraperRole field carries the enum: [cluster-scraper] constraint generated by the operator. Companion: aws/amazon-cloudwatch-agent-operator#399. otelContainerInsights.prometheusScrape.enabled defaults to false until operator and Target Allocator images with prometheusCR discovery, per-node allocation and scraper_role are released; enabling it requires pinning those images together. The per-node prometheusCR pipeline applies the same unit normalization as the cluster-scraper one, so a monitor's units do not depend on which agent scrapes it.

Routes a ServiceMonitor/PodMonitor to the central cluster-scraper agent via the cloudwatch.aws.amazon.com/scraper: cluster-scraper annotation on the monitor CR. The cluster-scraper gets its own Target Allocator and prometheusCR with scraperRole: cluster-scraper and consistent-hashing allocation; the per-node agent keeps the default (empty) role and per-node allocation. The Target Allocator ClusterRole/ClusterRoleBinding render once (all Target Allocators share the target-allocator-service-acct service account), so a second Target-Allocator-bearing agent no longer produces a duplicate-named object. The bundled CRD's scraperRole field carries the enum: [cluster-scraper] constraint generated by the operator. Companion: aws/amazon-cloudwatch-agent-operator#399. otelContainerInsights.prometheusScrape.enabled defaults to false until operator and Target Allocator images with prometheusCR discovery, per-node allocation and scraper_role are released; enabling it requires pinning those images together. The per-node prometheusCR pipeline applies the same unit normalization as the cluster-scraper one, so a monitor's units do not depend on which agent scrapes it.

This was referenced Jul 15, 2026

[amazon-cloudwatch-observability] Route SM/PM to cluster-scraper by annotation aws-observability/helm-charts#339

Open

[amazon-cloudwatch-agent-test] Add scraper routing integration tests aws/amazon-cloudwatch-agent-test#724

Open

musa-asad reviewed Jul 21, 2026

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musa-asad previously approved these changes Jul 24, 2026

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wenegiemepraise dismissed musa-asad’s stale review via 6950def September 4, 2026 10:28

Aakash-Dantre force-pushed the ta-annotation-scraper-routing branch 2 times, most recently from 329e93f to e4fe2d5 Compare September 23, 2026 12:41

Aakash-Dantre force-pushed the ta-annotation-scraper-routing branch from e4fe2d5 to cd3e40b Compare September 23, 2026 12:51

musa-asad and others added 5 commits September 25, 2026 15:37

Aakash-Dantre force-pushed the ta-annotation-scraper-routing branch from cd3e40b to afa7000 Compare September 25, 2026 14:39

Aakash-Dantre mentioned this pull request Oct 1, 2026

feat(target-allocator): per-node allocation and annotation-based SM/PM routing #415

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[amazon-cloudwatch-agent-operator] Route SM/PM by cloudwatch.aws/scraper annotation - #399

[amazon-cloudwatch-agent-operator] Route SM/PM by cloudwatch.aws/scraper annotation#399
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wenegiemepraise commented Jul 15, 2026

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wenegiemepraise commented Jul 15, 2026

Summary

What

Why annotation (not label)

Testing

Dependencies / stacking

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