[amazon-cloudwatch-agent-operator] feat(target-allocator): add per-node allocation strategy#398
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wenegiemepraise wants to merge 5 commits into
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[amazon-cloudwatch-agent-operator] feat(target-allocator): add per-node allocation strategy#398wenegiemepraise wants to merge 5 commits into
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…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.
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.
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.
Add a per-node allocation strategy so each CloudWatch agent (DaemonSet, one per node) scrapes only the ServiceMonitor/PodMonitor targets on its own node, eliminating cross-node/cross-AZ scrape traffic. Targets that cannot be matched to a node-local agent (node-less endpoints, nodes without a Ready agent) fall back to consistent-hashing so they are never silently dropped. - allocation/per_node.go: perNodeAllocator (node index, consistent-hashing fallback ring, unassigned tracking, descriptive logging) + registration. - allocation/strategy.go: Collector.NodeName, NewCollector(name, node), WithFallbackStrategy option, targets_unassigned gauge. - collector/collector.go: capture pod.Spec.NodeName, skip empty-NodeName pods, handle watch.Modified so a collector's node is picked up once scheduled (fixes targets being stuck on the fallback after a DaemonSet rollout). - target/target.go: GetNodeName() from __meta_kubernetes_*_node_name labels. - config + main: FallbackAllocationStrategy wiring. - apis/v1alpha1 + CRD: allocationStrategy enum gains "per-node". - internal/manifests/targetallocator/configmap.go: emit per-node strategy and the consistent-hashing fallback from the CR.
# Conflicts: # cmd/amazon-cloudwatch-agent-target-allocator/main.go
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Summary
Add a per-node allocation strategy to the Target Allocator so each CloudWatch Agent
(DaemonSet, one per node) scrapes only the ServiceMonitor/PodMonitor targets on its own
node — eliminating cross-node / cross-AZ scrape traffic. Targets without a resolvable node
fall back to consistent-hashing, so nothing is silently dropped.
Motivation
The fork registers only
consistent-hashing, a pure hash of the target URL with no nodeawareness — a pod on node A can be scraped by the agent on node B (inter-AZ data-transfer
cost + latency). This ports the upstream OpenTelemetry
per-nodestrategy into the fork.Changes
allocation/per_node.go— node-indexed allocator with consistent-hashing fallback andunassigned-target tracking
allocation/strategy.go— registerper-nodecollector/collector.go— captureCollector.NodeNamefrompod.Spec.NodeName(skip empty-NodeName pods; handle
watch.Modified)consistent-hashing | per-node)internal/manifests/targetallocator/configmap.go— emitallocation_strategy+allocation_fallback_strategyDependencies
commits. (Note: part of Fix Target Allocator startup crashes, PrometheusCR watcher, and Prometheus config pod restart #386 — the SD-metrics registration — has already landed on
main.)node-enrichment transforms). The chart default
per-noderequires this strategy registeredin the TA build.
Testing
allocationunit tests (per-node placement, fallback, unassigned tracking)consistent-hashing reproduces cross-node scrapes (validated live on EKS).