Terminal WebSockets

The RStudio Pro terminal pane uses WebSockets to communicate between the web browser and the session. If the attempt to connect with WebSockets fails, the terminal switches to a less responsive but generally more forgiving HTTP-based protocol.

Slow typing response in the terminal is a symptom of this slower protocol. You can check by starting a terminal, then going to Tools / Terminal / Terminal Diagnostics. Scroll down to Connection Information and look for “WebSocket connect error, switching to RPC”. This indicates that the terminal was unable to use WebSockets and has fallen back on the slower protocol.

Several settings are available for tuning the terminal’s use of WebSockets.

IDE settings

In the IDE under Tools > Global Options > Terminal, there is a check box Connect with WebSockets. Clearing the check box will cause terminals to always connect with the HTTP-based protocol.

Feature limit

Workbench

As mentioned earlier, the feature limit allow-terminal-websockets completely disables the use of WebSockets.

Advanced settings

The following settings may be modified by adding them to the /etc/rstudio/rsession.conf file.

Setting Default Purpose
websocket-ping-seconds 10 How often a keep-alive is sent over the WebSocket, in seconds. Set to 0 to disable keep-alives. Many proxies will close inactive WebSockets so keeping enabled is recommended.
websocket-connect-timeout 3 How long terminal waits (in seconds) for WebSocket to connect before switching to the HTTP protocol. If set to 0 then the timeout of the web browser’s WebSocket implementation will be used; this is often quite lengthy (minutes).
websocket-log-level 0

Controls logging of WebSocket diagnostics. These are for troubleshooting only, and will appear in the RStudio Pro R Console pane while enabled.

  • 0 = no WebSocket logging
  • 1 = log WebSocket errors
  • 2 = log WebSocket activity
  • 3 = log WebSocket errors and activity
websocket-handshake-timeout 5000 How long the server waits (in milliseconds) for WebSocket handshake to complete when connecting and disconnecting. Set to 0 to disable.

For example, this would double the number of keep-alive packets sent, wait longer before switching to HTTP, log information on WebSocket errors, and increase the handshake timeout to 15 seconds.

websocket-ping-seconds=5
websocket-connect-timeout=10
websocket-log-level=1
websocket-handshake-timeout=15000

For more background on the terminal feature, see this support article.

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