Question

I have a php page that needs to write to a database sometimes at the beginning of the script.

During a scheduled mysqldump backup, the page isn’t accessible, because it is trying to write to a table that is locked.

During the lock, MySql queues those sql updates, and after the backup is complete, they do get executed as desired. Yet my php page won’t display until the backup is complete.

However, since the updates do not return anything to the script, I wish they wouldn’t hang up my script during the lock; I hope there’s a way I can tell php to just send the sql update to mysql and don’t worry about confirmation that the update completed.

I want php to send the query to mysql, and then just continue on to the next line of php if the update doesn’t complete in one second.

I’m running php on a windows server, so I understand that some type of threading is not an option.

If there is way to set a timeout on that query (specifically), that might be ideal, but I don’t want to renege the sql update altogether if it times out. I still want MySQL to process it after the lock is gone.

What would you recommend (given that removing the sql updates altogether is not an option)?

Answer 1

For others that may come across this thread, I ultimately wrote this function to detect if the table is locked, and only do the SQL updates if it is NOT locked:

function isLocked($databaseName,$tableName)
    {
        $sql = "show open tables from `".$databaseName."` where `table`=`".tableName."` and In_use > 0;";
        $result = @mysql_query($sql);
        if (mysql_num_rows($result) != 0 )
        {
            return true;
        }
        else
        {
            return false;
        }
    }

(note: This function assumes the database connection is already established)

This works, because I’ve modified the code so that the sql updates will ultimately get done the next time the page is loaded without a lock in place.