Google App Script: LockService doesn't work - google-apps-script

Question

I'm trying to implement a chat-bot using GAS (google app script). And faced some troubles with LockService. It seems not to work properly or at all.
When i get new message from appropriate chat, i saved delay-value (8 seconds) for ignoring subsequent messages from this chat. I do this using lockService to avoid skipping concurrent messages.
However it doesn't work, and some messages leaved out.
My code:
function get_message_safely(chat_id, message) {
var lock = LockService.getScriptLock();
const delay = 8*1000; // 8 seconds
// save time of getting message
var get_time = (new Date()).getTime();
// lock
// set lock before accessing data
try {
if (lock.hasLock()) { // ==always false (for unknown reasons)
sendLog('get_message_safely/hasLock', 'lock = true' + '\n' + message);
}
lock.waitLock(10000); // wait 10 seconds for others' use of the code section and lock to stop and then proceed
} catch (error) {
sendLog('get_message_safely/lock_service', 'ОШИБКА: ' + error);
send_message(chat_id, "Наши сервера сейчас загружены. Отправьте сообщение повторно или попробуйте позже.");
lock.releaseLock();
return;
}
// get data from PropertiesService
var scriptProperties = PropertiesService.getScriptProperties();
var chat_access_flag = scriptProperties.getProperty(chat_id);
if (chat_access_flag != undefined) { // if chat already exist
if (chat_access_flag == 'false') { // access denied
sendLog('get_message_safely/lock_service', 'LockService: доступ запрещен.\n' + message);
lock.releaseLock();
return;
}
var lock_time = Number(chat_access_flag);
if (get_time <= lock_time) { // access denied: lock_time is still actual
sendLog('get_message_safely/lock_service', 'LockService: доступ запрещен т.к. время не прошло:\n' + lock_time + ' - ' + get_time + ' = ' + (lock_time - get_time) + '\n' + message);
lock.releaseLock();
return;
}
sendLog('get_message_safely/lock_service', 'LockService: доступ разрешен:\n' + lock_time + ' - ' + get_time + ' = ' + (lock_time - get_time) + '\nnew_lock_time: ' + (get_time + delay) + '\n' + message);
}
scriptProperties.setProperty(chat_id, get_time + delay); // if access is allowed, set new delay
// lock release
lock.releaseLock(); // release the lock
get_message(chat_id, message); // handling message
}
So, sometimes i have the case (when i send a lot messages at the same time), when lockService should handle it but it doesn't:
Case (example):
// lock_time == a;
// get 1 message: access allowed. So set new value to lock_time (=b)
// lock_time == b;
// get 2 message: access denied. get_time < lock_time (=b)
// lock_time still == b;
// get 3 message: access allowed: get_time > lock_time, where lock_time == a (!???). So set new value to lock_time (=c);
// lock_time == с (??)
// get 4 message: access denied: get_time < lock_time (=b)
Handling messages due to lockService should be done sequentially. But some messages for some reason access to PropertiesService and get same date at same time.
It's blowing my mind. Have you any ideas what's happening here?
And how can i reach desirable result?

Answer 1

After studying your code I see that .hasLock() always returns false. Please, forgive me if I am mistaken. In your scenario this could mean that neither .waitLock() nor .tryLock() was called before. To fix the issue you have to use one of the mentioned methods. You can read on the links some example usages. Please, ask me any question if you need further help.