What would cause PHP to ignore mysqli.reconnect setting? - php

Question

We have several different servers running the same PHP scripts, all of which use PHP mysqli connections/functions, and we noticed that, on one new server, we started getting many MYSQL Gone Away errors.
wait_timeout in MYSQL is set to 300 seconds on all servers, and this is the length of time it takes before the connection drops on this particular server (i.e. a wait of 301 seconds between queries in the code below produces the error, but 299 seconds does not).
However, all servers also have mysqli.reconnect set to 1 (On). According to documentation, mysqli.reconnect should mean that the dropped connection is reconnected automatically, however it definitely isn't.
Here is a code snippet that I've run that demonstrates the issue. It works on all servers except this particular server:
$mysqli = new mysqli('ip', 'username', 'pass', 'db');
if (mysqli_connect_errno()) {
printf("Connect failed: %s\n", mysqli_connect_error());
exit();
}
$query = "SELECT * FROM table LIMIT 1";
$result = $mysqli->query($query) or die($mysqli->error.__LINE__);
sleep(301);
$query = "SELECT * FROM table LIMIT 1";
$result = $mysqli->query($query) or die($mysqli->error.__LINE__);
mysqli_close($mysqli);
print "Finished\n";
exit;
I have also re-written the test script to use mysqli_ping() (since the documentation states that this function should reconnect automatically if mysqli.reconnect is set to 1), however this still does not reconnect, and the second query always produces the error that MySQL has gone away.
All servers are running slightly different versions of PHP. The server that fails is running 5.3.21, other servers are running 5.3.0 and 5.3.10.

Answer 1

Turned out the issue was with the MYSQLND driver. Our service provider basically recompiled PHP, and this resolved the issue.

Answer 2

There is a php bug filed about this, resolved as wontfix: https://bugs.php.net/bug.php?id=52561

Answer 3

I just came across this while looking for info about the mysqli.reconnect setting. According to the manual:
https://www.php.net/manual/en/mysqli.configuration.php#ini.mysqli.reconnect
Note: This php.ini setting is ignored by the mysqlnd driver.
That didn't specify whether it meant that it always would, or always would not, auto-reconnect. "Would not" seemed more likely, which is confirmed by the comment above noting that it was not happening when the setting was 1.
My issue was that I wanted a way to know when the connection had died (for error-reporting purposes, and so I could implement selective retrying of a failed DB operation in only that case). I don't know if there's a more direct way to check whether a DB connection is alive, but I found my way to the mysqli::ping() method. Except, if it silently auto-reconnected, I wouldn't know it had happened.
So my solution is to save/disable/restore the setting along with using ping(), like this:
if (!$result) { // DB operation failed
$save = ini_get('mysqli.reconnect'); // save setting
ini_set('mysqli.reconnect', 0); // disable it
$connected = $mysqli->ping(); // check connection
ini_set('mysqli.reconnect', $save); // restore setting
}
if ($connected) {
// Failure was something else. Handle that...
} else {
// Failure was due to dropped connection.
// Explicitly reconnect.
// Ok to retry operation...
}