Not like the instance implementation used prior, mysqlnd_ms makes use of a configuration dossier containing information regarding the place to failover. which means it's very effective (all the information is in memory), but in addition that it's static. the knowledge in regards to the masters and the slaves is saved in a configuration dossier in JSON structure just like the dossier in instance 6-6. the following, the grasp is thought to be read-write and the slaves are all read-only servers. instance 6-6. instance of mysqlnd_ms configuration dossier { "myapp": { "master": [ { "host": "master1. instance. com" } ], "slave": [ { "host": "slave1. instance. com", "port": "3306" }, { "host": "slave2. instance. com", "port": "3307" }, { "host": "slave3. instance. com", "port": "3308" } ] } } } whilst a connection is confirmed, the hostname is used as a key into the constitution in instance 6-6, and if a fit is located, the relationship info in a single of the entries below the secret's used as an alternative. Which connection info is used relies on the coverage set for the weight balancer. the burden balancer investigates the assertion to come to a decision the place to ship it. Any assertion beginning with decide on is taken into account a read-only assertion and should be despatched to the slave, whereas the other assertion is shipped to the grasp. you will discover instance code for utilizing mysqlnd_ms in instance 6-7. instance 6-7. personal home page code for utilizing mysqlnd_ms $QUERY = <<prepare($QUERY); if ($stmt) { $stmt->bind_param("d", $emp_no); $stmt->execute(); $stmt->bind_result($first_name, $last_name, $dept_name); whereas ($stmt->fetch()) print "$first_name $last_name $dept_name\n"; $stmt->close(); } else { echo "Error: " . $mysql->error; } The question includes choose first, so the plug-in will imagine that this can be a learn question and may be despatched to a learn slave. observe that the hostname given isn't a true hostname, yet fairly a connection with the myapp key within the configuration dossier. The plug-in will use this data to dispatch the question to the right kind server. Hierarchical Replication even supposing the grasp is kind of sturdy at dealing with plenty of slaves, there's a restrict to what percentage slaves it could possibly deal with sooner than the burden turns into too excessive for convenience (roughly 70 slaves for every grasp looks a pragmatic restrict, yet as you possibly detect, this relies much at the application), and an unresponsive grasp is usually an issue. In these instances, you could upload an additional slave (or a number of) as a relay slave (or easily relay), whose basically goal is to lighten the burden of replication at the grasp by way of taking good care of a number of slaves. utilizing a relay during this demeanour is named hierarchical replication. determine 6-4 illustrates a standard setup with a grasp, a relay, and a number of other slaves attached to the relay. determine 6-4. Hierarchical topology with grasp, relay, and slaves by means of default, the alterations the slave gets from its grasp usually are not written to the binary log of the slave, so if exhibit BINLOG occasions is finished at the slave within the prior setup, you won't see any occasions within the binlog.