Unexpected exception upon serializing continuation Google Apps Script

Question

I recently started getting the error "Unexpected exception upon serializing continuation" on a spreadsheet Google Apps Script when trying to debug. The error seem to start after I created a connection to the Google CloudSQL api. This error still occurs even after commenting out the jdbc object constructor. It appears that others have had this issue and needed a Google Tech to resolve the issue.

I have searched all of the discussion boards for a solution to this issue with no luck. Any chance there is a Google tech out there who could take a look under the hood for me? I would post code if I could determine what line was actually triggering the error.

EDIT:

Ok, I think I have discovered where the error is occuring. Seems to be the

var response = UrlFetchApp.fetch(url + nextPage,oauth_options);

in the while loop. Here is the entire function code.

function retrieveEvents(endTimeMinimum, updatedAfter, orderBy){      
//var url = 'https://www.googleapis.com/calendar/v3/calendars/' + source_cal + '/events?key=' + api_key + "&futureevents=true&orderBy=updated&sortOrder=descending&updatedMin=" + last_sync_date_formated;
//var url = 'https://www.googleapis.com/calendar/v3/calendars/' + source_cal + '/events?key=' + api_key + "&orderBy=updated&sortOrder=descending&updatedMin=" + last_sync_date_formated;

   var url = 'https://www.googleapis.com/calendar/v3/calendars/' + source_cal + '/events?key=' + api_key + "&singleEvents=true";

   if ((orderBy != null) && (orderBy != "")){
     url += "&orderBy=" + orderBy;
   }
   else url += "&orderBy=updated";

   if ((updatedAfter != null) && (updatedAfter != "")){
     url += "&updatedMin=" + updatedAfter;
   }
   else url += "&updatedMin=" + last_sync_dateTime;


   //if no endTimeMinimum is specified, the current time will be used.
   if (endTimeMinimum ==  null || endTimeMinimum == ""){
     endTimeMinimum = date_rfc339("Today");
   }

   url += "&timeMin=" + endTimeMinimum;

   Logger.log("Request URL:" + url);

   var largeString = "";
   var events = new Array();
   var nextPage = "";
   var jsonObj

   while(true){
     var response = UrlFetchApp.fetch(url + nextPage,oauth_options);
     largeString = response.getContentText();

     if ((largeString != null) && (largeString != "")) {
       jsonObj = JSON.parse(largeString);  
     }
     if ('items' in jsonObj) events = events.concat(jsonObj.items);
     if ('nextPageToken' in jsonObj){
       nextPage = "&pageToken=" + jsonObj.nextPageToken;
       continue;
     }
     break;
   }

   if (events.length == 0)return null;
     return events;
 }

Answer 1

OK, so I was able to make the problem go away by removing the try catch block inside a function that was called from inside a try catch block in the main function. I no longer am seeing the "Unexpected exception upon serializing continuation" when running the program from the debugger.

I wish I had a more solid answer on what causes this error and how to correct it.

Answer 2

In my experience, this is not an error caused by that line (or any other) specifically, but because an error is triggered within a loop. I haven't pinned down the exact replicable cause, but GAS seems to lose the loop pointer certain errors.

The best I can suggest is that any line that you suspect to causing an error within the while loop wrap with a try-catch that logs the error to the logger and proceeds. The loop pointer is then not lost and will debug as expected.