Nova API and Database State: Marker-Based Pagination Consistency

Direct answer

No. Nova's marker-based pagination for GET /servers behaves as a live cursor over the current database state, not as a snapshot. It does not guarantee that every resource present at the start of a traversal will be seen exactly once if instances are created, deleted, or updated between requests.

Likely explanation versus confirmed behavior

The marker is a cursor value evaluated against a sort key on each request. The API applies a keyset-style predicate rather than an OFFSET calculation, so each page reflects the rows that satisfy the predicate at query time. The following effects are the expected consequences of that model, though the exact default sort key and accepted parameters vary by Nova version and API microversion.

• Deleting a row behind the marker usually does not shift the cursor or create duplicates; it removes a row that was already passed.
• Deleting a row ahead of the marker means that instance will not appear in later pages, because it no longer exists when the query runs.
• Inserting a row that sorts before the marker can cause it to be omitted from the current traversal.
• Inserting a row that sorts after the marker may appear later in the same traversal.
• Updating a sort key can break exactly-once semantics: a processed row moved after the marker may repeat, and an unprocessed row moved before the marker may be skipped.

Steps for this case

1. If you need an exactly-once inventory, pause writes or export a consistent database snapshot and traverse that instead of the live API.
2. For routine listing, design clients to tolerate drift: accept that rows may be missed or repeated, and re-traverse when the dataset settles.
3. When your Nova version supports it, traverse using a stable, unique sort key rather than a mutable or non-unique field.
4. To verify behavior in your environment, run a no-write control traversal and a concurrent-write traversal with the same limit and marker, then diff the returned UUIDs page by page.

Version-sensitive details to confirm

Marker semantics, the default sort key and direction, and whether sort_key and sort_dir are accepted depend on the Nova release and API microversion. If your deployment spans multiple cells or read replicas, cursor stability may vary further. Treat the marker as a cursor, not a snapshot token, and confirm the generated query uses a keyset predicate rather than OFFSET before relying on pagination for incident analysis.

One missing diagnostic

If this question relates to a specific incident, provide the exact Nova version and API microversion together with the sort_key and sort_dir in use. Without those, only the general consistency model above can be offered.