Enable Alloy clustering to reduce DPM by ~50%#522
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1. Add alloy.clustering.enabled=true — tells the helm chart to create a headless service and pass --cluster.join-addresses, enabling peer discovery between replicas. DPM drops from ~2x to ~1x per series. 2. Increase memory limit from 1Gi to 2Gi — prod has more scrape targets than staging, and clustering adds memberlist overhead. Without this, prod Alloy pods OOMKill. No changes to controller type (stays as Deployment), deploy.sh, or smoke tests. Authored with Claude.
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Summary
Add
alloy.clustering.enabled: trueto helm values. This tells the Alloy helm chart to:alloy-cluster) for peer discovery--cluster.join-addresses=alloy-clusterto Alloy podsWith this, the two Alloy replicas discover each other and distribute scrape targets ~50/50, instead of both independently scraping all targets (doubling DPM).
This is a one-line change — no changes to
controller.type(stays as Deployment),deploy.sh, or smoke tests.Root cause
The Alloy River config already had
clustering { enabled = true }on servicemonitors and podmonitors, but the helm chart levelalloy.clustering.enabledwas not set. Without it, the chart doesn't create the headless service or pass--cluster.join-addresses, so pods can't discover each other. Logs showed:"no peer discovery configured: both join and discover peers are empty".Expected impact
Test plan