Run source if loop fails (RSelenium)

Question

I wrote a loop to go check a bunch of links and take screenshots. I often need to do these in the thousands. The loop I created works well for about 500 links and then my browser closes and I get the following error:

    Error: Summary: UnknownError
    Detail: An unknown server-side error occurred while processing the command.
    class: org.openqa.selenium.remote.UnreachableBrowserException

Is there a way to prevent this?

If not, how can I get R to run source code OpenBrowser.R if this happens?

Here is the script:

    for(i in 1:nrow(URL)){      
         remDr1$navigate(URL$Link[i])
         remDr1$setTimeout(type = "page load", milliseconds = 30000)
         remDr1$screenshot(file = URL$file[i])
         }

I haven't been able to understand how tryCatch works. Could you post an example of how I would use it in this code? — yake84
– yake84, Commented Jan 19, 2016 at 15:41

Indranil Gayen · Accepted Answer · 2016-01-19 15:27:31Z

4

Few things can be tried like :-

Try this function :- (it will wait till full page load. If required you can remove page_load_time_out or make in Inf)

wait_till_page_load<-function(page_load_time_out=60){
  t0<-Sys.time()
  while(remDr$executeScript("return document.readyState;")[[1]]!="complete" & (Sys.time()-t0)<=page_load_time_out){
    Sys.sleep(0.5)
  }
  invisible(0)
}

Use it like :-

for(i in 1:nrow(URL)){      
         remDr1$navigate(URL$Link[i])
         #remDr1$setTimeout(type = "page load", milliseconds = 30000)
         wait_till_page_load(500000000) # use suitable number
         try(remDr1$screenshot(file = URL$file[i]))
}

Try will prevent from breaking the loop.

answered Jan 19, 2016 at 15:27

Indranil Gayen

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