fix: synchronize WebSocket sends to prevent deflater crash#32
Merged
Conversation
OkHttp's MessageDeflater (permessage-deflate) is not thread-safe. Concurrent ws.send() calls from RelayPool's sendToAll/sendToReadRelays crash with 'Failed requirement' in MessageDeflater.deflate(). Add sendLock to serialize all writes to each WebSocket connection, including drainPendingMessages on connect.
barrydeen
added a commit
that referenced
this pull request
Feb 22, 2026
OkHttp's MessageDeflater (permessage-deflate) has multiple threading bugs that cause FATAL crashes: 1. Concurrent ws.send() → 'Failed requirement' in deflate() 2. Concurrent failWebSocket/close → NPE in Buffer.write() during DeflaterSink cleanup The sendLock from PR #32 only fixes case 1. Case 2 happens in OkHttp's internal cleanup path (failWebSocket → WebSocketWriter.close → MessageDeflater.close) which we cannot synchronize. Fix: strip Sec-WebSocket-Extensions header from server responses via a network interceptor. This prevents OkHttp from activating the deflater entirely. For Nostr's small JSON messages, compression savings are negligible compared to crash-free operation. The sendLock is retained as defense-in-depth.
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
1 participant
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
Summary
Fix FATAL EXCEPTION crash in OkHttp's
MessageDeflater.deflate().Problem
OkHttp's
MessageDeflater(used for permessage-deflate WebSocket compression) is not thread-safe. WhenRelayPool.sendToAll()iterates relays and callsrelay.send()from multiple coroutines concurrently, the deflater's internal state gets corrupted:Fix
Add
sendLock(synchronized) to serialize allws.send()calls per Relay instance, includingdrainPendingMessages()on connect.Testing