Transmit only single frame in Write when compression enabled too

[andersroos]

Hi I am experiencing a pretty weird behavior and I am unsure if this is intentional or not.

We have had problems with bad client performance when reading data from a websocket in a game client based on Unreal Engine.

I have investigated this and with compression enabled each message is chopped up in tiny frames (the problem surfaced when we run with 1.8.7 which had compression on by default). The problem with Unreal is that it only reads one frame per client tick (~8 milliseconds) by default.

When I inspect this in Wireshark it looks like every other frame has a 236 byte payload and every other has a 4 byte payload.

I also run it in the debugger and it looks like the server will send a frame for each write call from the flate lib (github.com/klauspost/compress) and it has a hard coded bufferFlushSize set to 240 which in turn causes all those individual calls to writeFrame.

Is this intentional?

[nhooyr]

Are you using Write or Writer? Write should write in a single frame whereas Writer unfortunately does write in two frames.

If you are using Write it's possible I forgot to add the code necessary to make it use a single frame with compression enabled.

[nhooyr]

Also are you using the latest version or are you on 1.8.7 still?

[andersroos]

Thanks for the response.

I have tested on 1.8.10 and it is the same behavior if compression is enabled (CompressionMode: websocket.CompressionNoContextTakeover).

The code uses Write (this method:

websocket/write.go

Line 44 in e3a2d32

func (c *Conn) Write(ctx context.Context, typ MessageType, p []byte) error {

).

I can make a minimal example to reproduce if it's helpful.

[nhooyr]

No need I see it, the problem is here:

websocket/write.go

Line 110 in e3a2d32

if !c.flate() {

I need to extend this code to allow for single frame compression.

[nhooyr]

I would suggest disabling compression till I get to this. Hopefully within the next 2 months.

[andersroos]

I would suggest disabling compression till I get to this. Hopefully within the next 2 months.

Thank you, will do.