Oracle 5.0 Reference Manual page 2607

Mysqlnd replication and load balancing plugin (mysqlnd_ms)
- Can't connect to MySQL server on '%s' (%d)
Unknown MySQL server host '%s'
codes and manually perform a fail over. The plugins philosophy is not to offer automatic fail over,
beyond master fail over, because fail over is not a transparent operation.
Example 20.256. Provoking a connection error
{
"myapp": {
"master": {
"master_0": {
"host": "localhost"
}
},
"slave": {
"slave_0": {
"host": "invalid_host_name"
},
"slave_1": {
"host": "192.168.78.136"
}
},
"lazy_connections": 1,
"filters": {
"roundrobin": [
]
}
}
}
Explicitly activating lazy connections is done for demonstration purposes, as is round robin load
balancing as opposed to the default
Example 20.257. Most basic failover
<?php
$mysqli = new mysqli("myapp", "username", "password", "database");
if (mysqli_connect_errno())
/* Of course, your error handling is nicer... */
die(sprintf("[%d] %s\n", mysqli_connect_errno(), mysqli_connect_error()));
/* Connection 1, connection bound SQL user variable, no SELECT thus run on master */
if (!$mysqli->query("SET @myrole='master'")) {
printf("[%d] %s\n", $mysqli->errno, $mysqli->error);
}
/* Connection 2, first slave */
$res = $mysqli->query("SELECT VERSION() AS _version");
/* Hackish manual fail over */
if (2002 == $mysqli->errno || 2003 == $mysqli->errno || 2004 == $mysqli->errno) {
/* Connection 3, first slave connection failed, trying next slave */
$res = $mysqli->query("SELECT VERSION() AS _version");
}
if (!$res) {
printf("ERROR, [%d] '%s'\n", $mysqli->errno, $mysqli->error);
} else {
/* Error messages are taken from connection 3, thus no error */
printf("SUCCESS, [%d] '%s'\n", $mysqli->errno, $mysqli->error);
$row = $res->fetch_assoc();
$res->close();
printf("version = %s\n", $row['_version']);
}
$mysqli->close();
?>
(%d). For example, the application may test for the error
type.
random once
2587
and
2005 (CR_UNKNOWN_HOST) -