Shiny server: socket hang up - r

Question

Update: I added the solution below
The problem
A little background: I am running Shiny server v1.5 on an Ubuntu precise server. Basically I have an rmarkdown page that allows the user to play with some parameters and then has a download button that generates a document using shiny like so:
```{r,echo=FALSE}
downloadHandler(
filename = "report.pdf",
content = function(file) {
knitr::knit2pdf("report.Rnw",envir=environment())
file.rename(normalizePath('report.pdf'), file)
}
)
```
The Shiny application works fine on my local machine, but crashes on the server. More specifically, the r markdown webpage works fine, but once I click the download button, the app crashes after about 30 seconds. The server logs indicate a socket time-out error:
[2016-02-24 03:38:52.240] [INFO] shiny-server - Starting listener on 0.0.0.0:3838
[2016-02-24 03:49:30.183] [ERROR] shiny-server - Uncaught exception: Error: socket hang up
[2016-02-24 03:49:30.184] [ERROR] shiny-server - Error: socket hang up
at createHangUpError (_http_client.js:215:15)
at Socket.socketCloseListener (_http_client.js:247:23)
at Socket.emit (events.js:129:20)
at TCP.close (net.js:485:12)
[2016-02-24 03:49:30.184] [INFO] shiny-server - Stopping listener on 0.0.0.0:3838
[2016-02-24 03:49:30.185] [INFO] shiny-server - Shutting down worker processes (with notification)
/opt/shiny-server/lib/main.js:364
throw err;
^
Error: socket hang up
at createHangUpError (_http_client.js:215:15)
at Socket.socketCloseListener (_http_client.js:247:23)
at Socket.emit (events.js:129:20)
at TCP.close (net.js:485:12)
This pdf takes quite a long time to generate (about five minutes), so I'm suspecting that I missed some time-out parameter somewhere. This is what I did in my shiny configuration:
run_as shiny;
app_init_timeout 999999;
app_idle_timeout 999999;
# Define a server that listens on port 3838
server {
listen 3838;
....
}
... but to no avail, because I'm still getting the error. Any suggestions would be greatly appreciated!
The solution
As mentioned by #daattali, you cannot have something take that long inside downloadButton, changing the server settings will not change anything about that. So I ended up splitting the generation & download functionality in two parts like so:
```{r, echo=FALSE}
shinyApp(
ui = fluidPage(
fluidRow(
column(2,
conditionalPanel(
condition = "!$('makeReport').hasClass('shiny-busy')",
actionButton("makeReport","Generate Report",icon=icon("file"))
)
),
column(4,
conditionalPanel(
condition = "!$('makeReport').hasClass('shiny-busy')",
uiOutput("downloadButton")
#downloadButton("downloadReport", "Download Report")
)
)
)
),
server = function(input, output) {
output$download_button <- renderUI({
downloadButton("downloadReport", "Download Results")
})
makeReportAction <- eventReactive(input$makeReport, {
...
knitr::knit2pdf("report.Rnw",envir=globalenv())
})
output$downloadButton <- renderUI({
makeReportAction() #only appear after first click on generate
downloadButton("downloadReport", "Download Report")
})
output$downloadReport <- downloadHandler(
filename = "report.pdf",
content = function(file) {
cat(paste("Does the pdf exist?",file.exists("report.pdf")))
file.rename(normalizePath('report.pdf'), file)
}
)
}
)
```

Answer 1

It might be the same problem someone else asked Joe Cheng about in the Google board last week
https://groups.google.com/forum/#!topic/shiny-discuss/4bL9jFaYly0
It looks like there's a time limit on the download handler, so maybe try seeing if it's possible to generate the file beforehand and only serving the file when the button is clicked