To complete refreshing of a cached oAuth token (for the project's service account) before subsequent GAS code executes, I have attempted using a while-loop as suggested in an answer to this SO post. But if the webapp script has been idle for longer than the token lifespan, an error still occurs -- the while-loop has not prevented subsequent code (that requires the token) from executing before the token has finished refreshing. Here is the code, where the function getToken() is called to generate the token and cache it:
var scrCache=CacheService.getScriptCache();
var clientToken=scrCache.get("clientToken");
var tokenExpire = scrCache.get("tokenExpire");
var timeLeft = tokenExpire - ((new Date()).getTime()/1000)
//check if token expired or expires soon
if(!clientToken || timeLeft< 400){
var expToken = tokenExpire;
var updateToken=getToken();//generate the new token and save to cache
var start = new Date();
// run while-loop until cache is refreshed; limit loop to maximum 15000 milliseconds = 15 seconds, to prevent endless loop
while (scrCache.get("tokenExpire") === expToken && !isTimeUp(start, 15000)){}
}
// function to prevent endless while-loop
function isTimeUp(startTime, milliSeconds){
var now = new Date();
return now.getTime() - startTime.getTime() > milliSeconds
}
//function to generate and cache token
function getToken(){
var clientJSON= JSON.parse(PropertiesService.getScriptProperties().getProperty("clientKey"));
var key = clientJSON.private_key;
var clientEmail = clientJSON.client_email;
var fetchScope=["https://www.googleapis.com/auth/spreadsheets","https://www.googleapis.com/auth/script.external_request"];
var serverToken = new init(key, fetchScope, clientEmail);
serverToken.addUser(clientEmail)
.requestToken();
var objectToken= serverToken.getTokens()[clientEmail];
scrCache.put("clientToken", objectToken.token, 3700); //cache token for multiple uses before it expires
scrCache.put("tokenExpire", objectToken.expire, 3700);
return scrCache.get("clientToken");
}
QUESTION: This isn't working when token has expired (script has been idle for more than an hour)--how should the oAuth token be generated and cached so that the first user after the script has been idle for more than an hour (so token is expired) does not get an error?
UPDATE: Pending answers to this question with better solutions, I have eliminated the while-loop and simply execute the getToken() function when the script's "if-test" finds the token expired or expiring soon. But in addition, I have set up a once/hour timed-trigger to execute the getToken() function, resetting the clientToken values. Conceivably a user might still get an error (if I understand, the trigger timing is somewhat random), but that should be very rare.
