Remove case-only distinctions before combining metrics in Managed Prometheus

Source facts

Azure Managed Prometheus treats metric names, label names and label values case-insensitively, unlike native self-managed Prometheus. Series differing only by letter case become one series. Samples arriving at the same timestamp for those case-only variants can have one randomly discarded, and returned casing is not predictable. Microsoft recommends producing or scraping with a consistent case. Microsoft Learn.

Applicability

Use this identity check when moving or combining self-managed metric streams. Decide whether case differences merely express inconsistent spelling or actually distinguish different entities in the producer’s model.

DSE recommendation

Review metric and label identities for case-only collisions before directing their producers into the same managed workspace. Where distinct entities currently rely on case, design a genuinely distinct identifier rather than simply lowercasing both into the same value. Coordinate naming changes with dashboard and rule owners, preserving the intended meaning of each series. Do not use the casing returned by one query as a durable identity convention.

Verification

In a bounded test, inspect representative source series and compare their intended identities with the managed result. Include case-only variants and simultaneous timestamps where appropriate, without claiming that the surviving variant will be deterministic. Confirm the revised identifiers remain distinct and that affected queries select the intended population. Retain the producer-to-series mapping as the acceptance evidence before expanding collection.

Official references

Microsoft Learn: Managed Prometheus query behavior. Source reviewed September 9, 2026.