Oracle 5.0 Reference Manual page 2598

Mysqlnd replication and load balancing plugin (mysqlnd_ms)
<?php
$mysqli = new mysqli("myapp", "username", "password", "database");
if (!$mysqli)
/* Of course, your error handling is nicer... */
die(sprintf("[%d] %s\n", mysqli_connect_errno(), mysqli_connect_error()));
if (!$mysqli->query("DROP TABLE IF EXISTS test") ||
!$mysqli->query("CREATE TABLE test(id INT)") ||
!$mysqli->query("INSERT INTO test(id) VALUES (1)"))
die(sprintf("[%d] %s\n", $mysqli->errno, $mysqli->error));
/* Explicitly allow eventual consistency and caching (TTL <= 60 seconds) */
if (false == mysqlnd_ms_set_qos($mysqli, MYSQLND_MS_QOS_CONSISTENCY_EVENTUAL, MYSQLND_MS_QOS_OPTION_CACHE,
die(sprintf("[%d] %s\n", $mysqli->errno, $mysqli->error));
}
/* To make this example work, we must wait for a slave to catch up. Brute force style. */
$attempts = 0;
do {
/* check if slave has the table */
if ($res = $mysqli->query("SELECT id FROM test")) {
break;
} else if ($mysqli->errno) {
die(sprintf("[%d] %s\n", $mysqli->errno, $mysqli->error));
}
/* wait for slave to catch up */
usleep(200000);
} while ($attempts++ < 10);
/* Query has been run on a slave, result is in the cache */
assert($res);
var_dump($res->fetch_assoc());
/* Served from cache */
$res = $mysqli->query("SELECT id FROM test");
?>
The example shows how to use the cache feature. First, you have to set the quality of service to
eventual consistency and explicitly allow for caching. This is done by calling mysqlnd_ms_set_qos.
Then, the result set of every read-only statement is cached for upto that many seconds as allowed with
mysqlnd_ms_set_qos.
The actual TTL is lower or equal to the value set with mysqlnd_ms_set_qos. The value passed to the
function sets the maximum age (seconds) of the data delivered. To calculate the actual TTL value the
replication lag on a slave is checked and subtracted from the given value. If, for example, the maximum
age is set to 60 seconds and the slave reports a lag of 10 seconds the resulting TTL is 50 seconds.
The TTL is calculated individually for every cached query.
Example 20.249. Read your writes and caching combined
<?php
$mysqli = new mysqli("myapp", "username", "password", "database");
if (!$mysqli)
/* Of course, your error handling is nicer... */
die(sprintf("[%d] %s\n", mysqli_connect_errno(), mysqli_connect_error()));
if (!$mysqli->query("DROP TABLE IF EXISTS test") ||
!$mysqli->query("CREATE TABLE test(id INT)") ||
!$mysqli->query("INSERT INTO test(id) VALUES (1)"))
die(sprintf("[%d] %s\n", $mysqli->errno, $mysqli->error));
/* Explicitly allow eventual consistency and caching (TTL <= 60 seconds) */
if (false == mysqlnd_ms_set_qos($mysqli, MYSQLND_MS_QOS_CONSISTENCY_EVENTUAL, MYSQLND_MS_QOS_OPTION_CACHE,
die(sprintf("[%d] %s\n", $mysqli->errno, $mysqli->error));
}
/* To make this example work, we must wait for a slave to catch up. Brute force style. */
2578