fix: Disable compression for websocket dRPC transport (#145)

bryphe-coder · web-flow · commit 03ed951c8452 · 2022-02-02T13:32:03.000-08:00
There is a race condition in the interop between the websocket and `dRPC`: https://github.com/coder/coder/runs/5038545709?check_suite_focus=true#step:7:117 - it seems both the websocket and dRPC feel like they own the `byte[]` being sent between them. This can lead to data races, in which both `dRPC` and the websocket are writing. This is just tracking some experimentation to fix that race condition ## Run results: ## - Run 1: peer test failure - Run 2: peer test failure - Run 3: `TestWorkspaceHistory/CreateHistory` - https://github.com/coder/coder/runs/5040858460?check_suite_focus=true#step:8:45 ``` status code 412: The provided project history is running. Wait for it to complete importing!` ``` - Run 4: `TestWorkspaceHistory/CreateHistory` - https://github.com/coder/coder/runs/5040957999?check_suite_focus=true#step:7:176 ``` workspacehistory_test.go:122: Error Trace: workspacehistory_test.go:122 Error: Condition never satisfied Test: TestWorkspaceHistory/CreateHistory ``` - Run 5: peer failure - Run 6: Pass ✅ - Run 7: Peer failure ## Open Questions: ## ### Is `dRPC` or `websocket` at fault for the data race? It looks like this condition is specifically happening when `dRPC` decides to [`SendError`]). This constructs a new byte payload from [`MarshalError`](https://github.com/storj/drpc/blob/f6e369438f636b47ee788095d3fc13062ffbd019/drpcwire/error.go#L15) - so `dRPC` has created this buffer and owns it. From `dRPC`'s perspective, the callstack looks like this: - [`sendPacket`](https://github.com/storj/drpc/blob/f6e369438f636b47ee788095d3fc13062ffbd019/drpcstream/stream.go#L253) - [`writeFrame`](https://github.com/storj/drpc/blob/f6e369438f636b47ee788095d3fc13062ffbd019/drpcwire/writer.go#L65) - [`AppendFrame`](https://github.com/storj/drpc/blob/f6e369438f636b47ee788095d3fc13062ffbd019/drpcwire/packet.go#L128) - with finally the data race happening here: ```go // AppendFrame appends a marshaled form of the frame to the provided buffer. func AppendFrame(buf []byte, fr Frame) []byte { ... out := buf out = append(out, control). // <--------- ``` This should be fine, since `dPRC` create this buffer, and is taking the byte buffer constructed from `MarshalError` and tacking a bunch of headers on it to create a proper frame. Once `dRPC` is done writing, it _hangs onto the buffer and resets it here__: https://github.com/storj/drpc/blob/f6e369438f636b47ee788095d3fc13062ffbd019/drpcwire/writer.go#L73 However... the websocket implementation, once it gets the buffer, it runs a `statelessDeflate` [here](https://github.com/nhooyr/websocket/blob/8dee580a7f74cf1713400307b4eee514b927870f/write.go#L180), which compresses the buffer on the fly. This functionality actually [mutates the buffer in place](https://github.com/klauspost/compress/blob/a1a9cfc821f00faf2f5231beaa96244344d50391/flate/stateless.go#L94), which is where get our race. In the case where the `byte[]` aren't being manipulated anywhere else, this compress-in-place operation would be safe, and that's probably the case for most over-the-wire usages. In this case, though, where we're plumbing `dRPC` -> websocket, they both are manipulating it (`dRPC` is reusing the buffer for the next `write`, and `websocket` is compressing on the fly). ### Why does cloning on `Read` fail? Get a bunch of errors like: ``` 2022/02/02 19:26:10 [WARN] yamux: frame for missing stream: Vsn:0 Type:0 Flags:0 StreamID:0 Length:0 2022/02/02 19:26:25 [ERR] yamux: Failed to read header: unexpected EOF 2022/02/02 19:26:25 [ERR] yamux: Failed to read header: unexpected EOF 2022/02/02 19:26:25 [WARN] yamux: frame for missing stream: Vsn:0 Type:0 Flags:0 StreamID:0 Length:0 ``` # UPDATE: We decided we could disable websocket compression, which would avoid the race because the in-place `deflate` operaton would no longer be run. Trying that out now: - Run 1: ✅ - Run 2: https://github.com/coder/coder/runs/5042645522?check_suite_focus=true#step:8:338 - Run 3: ✅ - Run 4: https://github.com/coder/coder/runs/5042988758?check_suite_focus=true#step:7:168 - Run 5: ✅
diff --git a/coderd/provisionerdaemons.go b/coderd/provisionerdaemons.go
@@ -48,7 +48,10 @@ func (api *api) provisionerDaemons(rw http.ResponseWriter, r *http.Request) {
 
 // Serves the provisioner daemon protobuf API over a WebSocket.
 func (api *api) provisionerDaemonsServe(rw http.ResponseWriter, r *http.Request) {
-	conn, err := websocket.Accept(rw, r, nil)
+	conn, err := websocket.Accept(rw, r, &websocket.AcceptOptions{
+		// Need to disable compression to avoid a data-race
+		CompressionMode: websocket.CompressionDisabled,
+	})
 	if err != nil {
 		httpapi.Write(rw, http.StatusBadRequest, httpapi.Response{
 			Message: fmt.Sprintf("accept websocket: %s", err),
