WebSocket data race in send path under backpressure#1160
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IvanArkhipov1999 wants to merge 2 commits into
Open
WebSocket data race in send path under backpressure#1160IvanArkhipov1999 wants to merge 2 commits into
IvanArkhipov1999 wants to merge 2 commits into
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Hello!
When the server sends WebSocket messages faster than the client can read them, TCP backpressure appears and async writes take longer to complete.
At the same time, new messages are still pushed into Crow's outgoing buffer from another thread. As a result, one thread appends to the buffer while another thread swaps/reads it in do_write().
This causes a data race, buffer corruption, and eventually broken WebSocket frames on the client side (for example: "Invalid frame header").
I fixed the problem by protecting write_buffers_ with a mutex, and after that the issue disappeared.