PHP的睡眠和MySQL不相处

Question

I have a program that works in run-once mode, but fails when I run it in background with a do-while-true loop that includes a sleep(60) delay.

if ($debug || $run_once) {check_mail($domain_mail_box, $mailboxes); exit;} 
    else {
        do {
            check_mail($domain_mail_box, $mailboxes);

#       sleep 60;
#       exec('sleep 60'); # wait a minute after completing each run
            $i=0; do { $i++; } while ($i < 3000000001);
        } while (TRUE);
    }
    exit(0);

Actually, all three of these attempts to get it to work properly fail. It's odd because I have it running beautifully on another server/system. (Both are dedicated CentOS boxes.)

The failure is a MySQL failure. As part of the script, it writes to a log. The run-once and first runs with the delay write something like this for mysql_stat($Link): 0: Uptime: 605079 / 1: Threads: 2 / 2: Questions: 17458285 / 3: Slow queries: 0 / 4: Opens: 1287520 / 5: Flush tables: 1 / 6: Open tables: 1024 / 7: Queries per second avg: 28.852 /

but once I insert the delay, I get the dreaded: 0: MySQL server has gone away / from mysql_stat.

Any ideas what's going on?

Answer 1

Hmmm. I think I've found some information that sheds light on my problem: this comment from http://php.net/manual/en/mysqli.close.php . I'm considering the problem explained, if not solved. I'm actually solving by just creating and destroying the db link each time the program runs. Simple enough and no great overhead, I hope.

At least with PHP5.3.2 and Windows connecting by tcp, this differs by the old mysql_close() function in that it does not actually close out the tcp socket being used. You should always use mysqli_kill() function before mysqli_close() to actually close and free up the tcp socket being used by PHP. Garbage collection after script execution nor mysqli_close() do not kill the tcp socket on their own. The socket would otherwise remain in 'wait' state for approximately 30 seconds, and any additional page loads/connection attempts would only add to the total number of open tcp connections. This wait time does not appear to be configurable via PHP settings.

Answer 2

In your comment you said, that you want to use timer in order to control data sync between function executions.

Cron jobs are much more reliable approach. Thing, that you are trying to implement is an ugly solution.

Trick that you should use in your case:

1) Make a cron that runs every minute, and do mail logic.

2) Add table 'cron_locks' to database with name column. When your cron starts, you check if a there is a row in that table by name.

3) If lock is set, you should skip cron. If lock is not set - you set it.

4) In the end of function you remove lock from db.

Please ask me for further explanation, if I was not clear enough. I believe that this is correct solution for your problem.