DAPI responses are not compressed (rs-dapi defers to Envoy, Envoy has no compressor) #5576

Summary

DAPI responses, including proofs, are currently sent uncompressed. Neither rs-dapi nor the Envoy gateway compresses them, but the code says Envoy does:

• packages/rs-dapi/src/clients/drive_client.rs:64: "Compression (gzip) is intentionally DISABLED at rs-dapi level; Envoy handles it."
• packages/dashmate/templates/platform/gateway/envoy.yaml.dot: the HTTP filter chain is cors → grpc_web → ratelimit → router, with no envoy.filters.http.compressor.
• tonic's gzip/zstd features and send_compressed / accept_compressed are not enabled in rs-dapi, dapi-grpc, or rs-dapi-client.

Defacto raised this in Slack. I measured how much it would actually save.

Measurement

I extracted the raw grovedb_proof bytes from the recorded SDK test vectors (packages/rs-sdk/tests/vectors, at 371a3b3): 162 proofs, 116 unique, all ≤ 4.4 KB. Each one was compressed on its own, the way gRPC compresses messages.

gzip -6, zstd -3 and brotli -q 5 land within a couple of points of each other, so the codec choice matters little. The savings come from embedded payloads (contract schemas, document bodies, vote-poll keys). The 32-byte Merk hashes barely compress.

Caveats: these vectors come from small test networks. Mainnet trees are deeper, so hash-heavy proofs will compress somewhat less, while large document queries will likely compress more. Response metadata and the 96-byte signature were not included.

Proposal

1. Add an Envoy compressor filter (gzip, and zstd/brotli if wanted) with a min_content_length threshold of roughly 1 KB, so small hash-only responses skip it. This also covers grpc-web/browser clients. Alternatively, enable tonic compression in rs-dapi.
2. Make sure clients advertise grpc-accept-encoding / Accept-Encoding: rs-dapi-client (native and tonic-web-wasm-client) and js-dapi-client.
3. Fix or remove the misleading comment in drive_client.rs.
4. Check evonode CPU cost under load before turning it on by default.

@shumkov could you take a look and improve this?