Atlas auto-scaling gating by oplog window and its alerts
Parent: Oplog sizing under storage auto-scaling · Published reference · snapshot 2026-10-30
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Source-anchored research for Atlas auto-scaling gating by oplog window and its alerts. Run status: COMPLETED.
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How it works
- Atlas provides the event condition "Auto-scaling: Disk auto-scaling didn't initiate due to insufficient oplog size" when insufficient oplog size prevents disk expansion. (medium confidence) (verified as of 2026-10-14) [source]
- Stacktape exposes disableDiskScaling separately from minimum and maximum cluster-tier bounds in its MongoDB Atlas integration; investigate the deployed configuration when storage scaling is expected but absent. (low confidence) (verified as of 2025-12-02) [source]
Problems, failure modes and limitations
- Predictive operational-node scale-up has its own insufficient-oplog alert; predictive scaling therefore also exposes an oplog-related failure condition. (medium confidence) (verified as of 2026-10-14) [source]
- Auto-scaling event alerts apply to every cluster in a project and cannot be scoped to individual clusters; each notification identifies the triggering cluster by name and ID. (low confidence) (verified as of 2026-10-14) [source]
- The Atlas Kubernetes generated API reference explicitly states that both the selected tier's maximum memory and oplog size can limit storage auto-scaling; an enabled diskGB flag alone does not remove these limits. (low confidence) (verified as of 2026-10-30) [source]
Facts and statements
- Atlas Core delays an auto-scaling event until the oplog window covers the estimated scaling time; oplog sufficiency is a prerequisite beyond merely enabling storage auto-scaling. (medium confidence) (verified as of 2026-10-14) [source]
- Separate insufficient-oplog event alerts identify blocked compute scale-up for operational nodes in the base tier and analytics nodes in the analytics tier. (medium confidence) (verified as of 2026-10-14) [source]
- Operators configure auto-scaling event notifications in project alert settings and can select recipients and delivery methods; auto-scaling events can also be inspected in the project Activity Feed. (medium confidence) (verified as of 2026-10-14) [source]
- Atlas exposes oplog monitoring independently of blocked-scaling events: the oplog-window alert thresholds approximate time retained on the primary, while replication headroom compares the sync-source window with secondary replication lag. (low confidence) (verified as of 2026-10-14) [source]
- The documented oplog scaling gate is edition-specific: the minimum oplog retention window does not affect Atlas Infinite auto-scaling. (low confidence) (verified as of 2026-10-14) [source]
- IBM MAS DevOps documents an optional Atlas cluster-health alert configuration that includes an oplog-window alert below one hour; this is an integration threshold, not evidence that Atlas always requires a one-hour window for scaling. IBM labels its Atlas provider proof-of-concept and unsuitable for production. (low confidence) (verified as of 2026-10-30) [source]
Children
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