Adobe Air SQLite synchronous busy timeout / SQLite concurrent access / avoid busy loop

问题

this is my first post here. I'm asking because I ran out of clues and I was unable to find anything about this specific issue.

My question is: In Adobe AIR, is there a way to do a synchronous usleep() equivalent (delay execution of 200ms), alternatively is there a way to specify the SQLite busy timeout somewhere?

I have an AIR application which uses the database in synchronous mode because the code cannot cope with the need of events/callbacks in SQL queries.

The database sometimes is accessed from another application, such that it is busy. Hence the execute() of a statement throws SQLerror 3119 detail 2206. In this case the command shall be retried after a short delay.

As there is another application running on the computer I want to try to avoid busy waiting, however I'm stuck with it because of three things:

First, I was unable to find a way to give the SQLConnection a busy timeout value, like it is possible in C with the function sqlite3_busy_timeout()

Second, I was unable to find the equivalent of the C usleep() command in Adobe AIR / Actionscript.

Third, I am unable to use events/timers/callbacks etc. at this location. The SQL execute() must be synchronous because it is called from deeply nested classes and functions in zillion of places all around in the application.

If the application could cope with events/callbacks while doing SQL I would use an asynchronous database anyway, so this problem cannot be solved using events. The retry must be done on the lowest level without using the AIR event processing facility.

The lowest level of code looks like:

private static function retried(fn:Function):void {
    var loops:int = 0;
    for (;;) {
        try {
            fn();
            if (loops)
                trace("database available again, "+loops+" loops");
            return;
        } catch (e:Error) {
            if (e is SQLError && e.errorID==3119) {
                if (!loops)
                    trace("database locked, retrying");
                loops++;
                // Braindead AIR does not provide a synchronous sleep
                // so we busy loop here
                continue;
                }
            trace(e.getStackTrace());
            trace(e);
            throw e;
        }
    }
}

One sample use of this function is:

protected static function begin(conn:SQLConnection):void {
    retried(function():void{
        conn.begin(SQLTransactionLockType.EXCLUSIVE);
    });
}

Output of this code is something like:

database locked, retrying
database available again, 5100 loops

Read: The application loops over 500 times a second. I would like to reduce this to 5 loops somehow to reduce CPU load while waiting, because the App shall run on Laptops while on battery.

Thanks.

-Tino

来源：https://stackoverflow.com/questions/4046421/adobe-air-sqlite-synchronous-busy-timeout-sqlite-concurrent-access-avoid-bus

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usleep