Question
Does ngrok's offset‑based pagination remain stable when inspection data is purged mid‑scan?
Mira River
0 reputation · 04 Jan 2023, 11:31 UTC
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0 reputation · 04 Jan 2023, 11:31 UTC
When using ngrok’s inspection API to page through request logs, clients typically combine a fixed limit with an increasing offset to retrieve successive batches. Ngrok automatically removes older inspection entries after a configurable retention period, which can change the total number of stored requests while a pagination walk is in progress.
This raises uncertainty about whether the offset‑based approach guarantees non‑overlapping, gap‑free pages when the underlying dataset may shrink between requests. Understanding the exact behavior helps decide if additional client‑side checks are needed.
Does specifying a fixed limit and incrementing offset by the previous limit still produce distinct, consecutive pages if ngrok purges entries during the walk?
What does the API return when an offset points to data that has already been deleted?
Should clients rely on the actual count returned in each page to compute the next offset instead of a fixed increment?
No, offset-based pagination does not remain stable when data is purged mid-scan. If the underlying dataset shrinks because older entries are deleted, the remaining records shift their positions. This causes the "window" of the next request to slide forward, potentially skipping records that have shifted into the previously retrieved offset range.
It is important to verify which pagination method your specific ngrok endpoint uses. While the question assumes an offset-based approach, the ngrok public inspection API typically employs cursor-based pagination (using parameters like before_id or after_id). These two methods behave differently during purges:
| Method | Behavior During Purge | Result |
|---|---|---|
| Offset-based | Indices shift as records are removed from the start of the list. | Gaps/Skipped records. |
| Cursor-based | The pointer remains tied to a specific record ID regardless of total count. | Stable sequence (unless the cursor record itself is purged). |
If you are using a cursor-based system and the record acting as your cursor is purged between requests, the API will typically return an error indicating the reference is invalid or return an empty set. In a theoretical offset-based system, the API will not return an error; it will simply return the next available records at that index, unaware that the data has shifted.
To ensure data integrity during a scan, follow these steps:
ngrokbefore_id or after_id, you are using cursors. If you see offset or page, you are using offsets.offset + limit). Instead, use the next_page URI or the specific cursor ID provided in the API response body to fetch the subsequent batch.limit allowed by the API to reduce the number of round-trips.Diagnostic Detail Needed: Please confirm the exact API endpoint and the specific query parameters (e.g., offset vs after_id) being used, as this determines whether the risk is "skipped records" (offset) or "broken pointers" (cursor).
Use comments to ask for clarification. Post a solution as an answer.
33,275 reputation · 04 Jan 2023, 17:57 UTC
Ngrok’s inspection API returns a total field that reflects the current number of stored requests after any purge. If you compute the next offset as previous offset + limit, you may skip records when entries are deleted before your current offset because the underlying indices shift. A safer approach is to set the next offset to previous offset + length of returned page (i.e., the actual count of items received). This uses the API‑reported count and guarantees you never jump over remaining records, even if the total shrinks. When the offset exceeds the updated total, the API returns an empty array with a 200 status and the reduced total.