random "permission denied" issues

[Johannes B. Ullrich]

I am having a very odd issue with one of my mysql 4.1.14 servers.
Randomly, the server returns "permission denied" to queries even if
identical queries succeeded within the same connection.

To test the problem, I setup a script that connects to the database, and
issues the same query 50,000 times. Out of the 50,000 attempts, about 10
fail, but the exact number varies. The error message in all cases is:

SELECT command denied to user 'user'@'host' for table 'example'

There are two web servers that use the same database. Both web servers
have this problem.

Here is a test script I use to illustrate the problem:

[EMAIL PROTECTED]($host,$user$password);
while ($i<50000) {
 $x=mysql_query($query);
 if ( $x) {
        print "$i worked!<BR>";
 } else {
        print "$i ERROR! ".mysql_error()."<BR>";
 }
 $i++;
}

I did not set up any mysql rate limits. The database is 'busy' but not
extreme (mytop shows about 100 queries/sec, 99.91% key efficiency)
usually about 10-20 threads. Query cache is enabled (and the above query
should take advantage of it). Database and Web Server are on the same
LAN separated by a firewall.

The system is a RedHat ES system, with MySQL rpms from mysql.com (i386),
recent 2.4 kernel.

Any  ideas?

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