Connection fails after a minute of inactivity

[christakopoulosa]

Log output
2018-10-15T10:52:36.905038+00:00 heroku[router]: at=error code=H15 desc="Idle connection" method=GET path="/websocket/" host=myapp.herokuapp.com request_id=62ff6c68-a766-46a2-9a44-f3f4f6aebab0 fwd="165.225.81.40" dyno=web.1 connect=1ms service=77186ms status=503 bytes= protocol=https

I want to use my heroku app as a dashboard so I would have extended periods of inactivity. How is that possible without my application shutting down due to an idle connection?

[virtualstaticvoid]

Hi @christakopoulosa

This is a known issue on Heroku, since websocket connections are disconnected after a period of inactivity. See the Heroku documentation on HTTP Routing - Timeouts and Long-polling and streaming responses for more information.

The simplest way to solve it, is to have a "keep alive" mechanism, as the following example shows, taken from shiny issues #2110.

Here's a simple solution to increment a counter every 10 seconds.

JS

var socket_timeout_interval;
var n = 0;

$(document).on('shiny:connected', function(event) {
  socket_timeout_interval = setInterval(function() {
    Shiny.onInputChange('alive_count', n++)
  }, 10000);
});

$(document).on('shiny:disconnected', function(event) {
  clearInterval(socket_timeout_interval)
});

CSS

#keep_alive {
  visibility: hidden;
}

server.R

output$keep_alive <- renderText({
  req(input$alive_count)
  input$alive_count
})

ui.R

textOutput("keep_alive")

Furthermore, the Shiny documentation has a article on Reconnecting to Shiny apps which may help, although I haven't tried this.

See also issue #97.