feat: providers result limits for JSON and NDJSON#149
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JSON delegated routing responses under-delivered: boxo's DefaultRecordsLimit of 20 acted as a pre-filter, and cacheFallbackIter silently dropped records without addresses. Production at delegated-ipfs.dev returned ~4 providers on JSON vs ~17 on NDJSON for the same CID. - raise the JSON cap to 100 and add a streaming cap of 1000, matching HTTP Routing v1 section 4.1.5; expose both as `--records-limit` and `--streaming-records-limit` with `SOMEGUY_*` env vars; reject negative input, 0 disables the cap - over-fetch from the underlying router by 3x (cap 3000) so that, after cacheFallbackIter drops addr-less records, the surfaced count is close to the caller's limit; cap the final stream via a new limitedIter wrapper
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| // cacheFallbackOverfetchMax caps the over-fetched limit so a large | ||
| // caller-side limit cannot blow up the DHT walk. Sized at 3x | ||
| // DefaultStreamingRecordsLimit so the multiplier applies on the | ||
| // streaming path too. The routing timeout bounds wall-clock. | ||
| cacheFallbackOverfetchMax = 3000 |
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What is meant by blow up the DHT walk?
IIRC the limit passed to FindProviders() is just an upper-bound allowing the DHT client to terminate the DHT walk early if it has found enough providers. The DHT client will not do extra work if it didn't find enough providers, it will simply stop and return after it has queried the 20 closest peers.
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Someguy supports JSON (buffered) and NDJSON (streaming) response types.
Problem
JSON delegated routing responses under-delivered: iiuc boxo's
DefaultRecordsLimitof 20 acted as a pre-filter, and cacheFallbackIter silently dropped records without addresses.Anecdotally (cc @aschmahmann), production at
delegated-ipfs.devreturned ~4 providers on JSON (when opened in browser) vs ~17 on NDJSON for the same CID (/ipns/ipfs.tech).As a side problem, NDJSON stream had no cap, which is a bad default.
Fix (This PR)
--records-limitand--streaming-records-limitwithSOMEGUY_*env vars; reject negative input, 0 disables the cap