Add support for gzipping messages in ws subscriptions

[preston-evans98]

Description

This PR adds support for gzipping messages on the events and transactions websockets using the ?compression=gzip query param. When gzip is enabled...

• Messages are chunked and encoded into a json array with at most 128 messages before being compressed and sent
• Errors json encoded, gzipped, and sent immediately

[greptile-apps]

Greptile Overview

Greptile Summary

Added gzip compression support for WebSocket subscriptions via ?compression=gzip query parameter. When enabled, messages are batched (max 128), JSON-encoded into arrays, gzip-compressed, and sent as binary frames.

Key Changes:

• Added CompressionMode enum and CompressionQuery struct to parse query params
• Implemented serve_generic_ws_subscription_with_config with conditional compression logic
• Updated /sequencer/events/ws and /sequencer/txs/ws endpoints to accept compression param
• Added comprehensive tests validating gzip magic bytes, batching, and backward compatibility
• Used flate2 with rust_backend for compression

Observations:

• Other WebSocket endpoints (/sequencer/txs/:tx_hash/ws, /sequencer/txs/submit/ws, and test-utils endpoints) were not updated with compression support
• Implementation maintains backward compatibility (default is no compression)
• Proper error handling: errors are flushed before sending compressed, and non-recoverable errors terminate connection

Confidence Score: 4/5

• Safe to merge with minor considerations about endpoint coverage
• Well-implemented feature with comprehensive tests and proper error handling. Score of 4 (not 5) due to inconsistent application across WebSocket endpoints - some endpoints support compression while others don't, which may confuse users
• Consider whether rest_api.rs:425 (axum_get_tx_ws) should also support compression for consistency

Important Files Changed

Filename	Overview
crates/full-node/sov-sequencer/src/rest_api.rs	Added compression query param to events and transactions endpoints; other WS endpoints not updated
crates/utils/sov-rest-utils/src/lib.rs	Implemented gzip compression with batching, proper error handling, and backward compatibility
crates/utils/sov-rest-utils/src/ws_tests.rs	Added comprehensive tests for compression mode, gzip roundtrip, and backward compatibility

[greptile-apps]

_{3 files reviewed, 1 comment}

_{Edit Code Review Agent Settings | Greptile}

[greptile-apps]

Additional Comments (1)

crates/full-node/sov-sequencer/src/rest_api.rs
Consider adding compression support to axum_get_tx_ws for consistency with other subscription endpoints

_{Note: If this suggestion doesn't match your team's coding style, reply to this and let me know. I'll remember it for next time!}

Prompt To Fix With AI

This is a comment left during a code review.
Path: crates/full-node/sov-sequencer/src/rest_api.rs
Line: 425:425

Comment:
Consider adding compression support to `axum_get_tx_ws` for consistency with other subscription endpoints

<sub>Note: If this suggestion doesn't match your team's coding style, reply to this and let me know. I'll remember it for next time!</sub>

How can I resolve this? If you propose a fix, please make it concise.

[codecov]

Codecov Report

❌ Patch coverage is 77.43363% with 51 lines in your changes missing coverage. Please review.
✅ Project coverage is 77.8%. Comparing base (4f8c280) to head (17c07cb).
⚠️ Report is 16 commits behind head on dev.

Files with missing lines	Patch %	Lines
crates/utils/sov-rest-utils/src/lib.rs	60.2%	39 Missing ⚠️
crates/utils/sov-rest-utils/src/ws_tests.rs	88.4%	12 Missing ⚠️

Additional details and impacted files

Files with missing lines	Coverage Δ
crates/full-node/sov-sequencer/src/rest_api.rs	73.3% <100.0%> (-3.3%)	⬇️
crates/utils/sov-rest-utils/src/ws_tests.rs	84.4% <88.4%> (ø)
crates/utils/sov-rest-utils/src/lib.rs	61.3% <60.2%> (-13.7%)	⬇️

... and 16 files with indirect coverage changes

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[bkolad]

send_compressed_bytes calls socket.feed(..), so this error might not be sent in some cases (in the uncompressed branch, we call socket.send) is that ok? Let's rename send_compressed_bytes to feed_compressed_bytes?

[bkolad]

Here we send an uncompressed error even if config.compress == true

[bkolad]

Approving, provided my comments are addressed.