Introduction to MySQL Group Replication

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MySQL Group Replication is a plugin that provides a distributed replication solution based on a multi-master replication model, built on top of MySQL Replication. It was introduced in MySQL 5.7.17. MySQL Group Replication ensures virtually instantaneous synchronization of transactions between different MySQL servers, making it an ideal solution for high-availability read-write workloads.

MySQL Group Replication Features

MySQL Group Replication has several features that make it a robust and flexible solution for data replication. Some of these features include:

• Multi-master model: MySQL Group Replication uses a multi-master model, which means that you can write to any node in the group and the transaction will be replicated to all other nodes . This is different from standard MySQL Replication, which uses a master-slave model.
• Synchronized Replication: Replication is performed synchronously, which means that transactions are committed on all nodes before being committed to the client. This ensures data consistency across all nodes.
• High Availability: MySQL Group Replication provides high availability through automatic failure detection and automatic recovery. If a node fails, the group automatically elects a new master and continues to operate without interruption.
• Read Scalability: Since all reads can be served by any node, MySQL Group Replication provides excellent read scalability.

How MySQL Group Replication works

MySQL Group Replication works over a group communication protocol that allows nodes to communicate with each other to determine the state of the group. The group communication protocol is based on a distributed consensus algorithm, which ensures that all transactions are applied in the same order on all nodes.

When a transaction is sent to a node, it is first applied locally and then sent to all other nodes in the group. Each node then applies the transaction to its own copy of the data. Once the transaction has been applied on all nodes, it is committed to the client.

If a node fails, the group communication protocol detects the failure and removes the node from the group. If the node that failed was the master, a new master is automatically elected. The new master then takes responsibility for coordinating transaction replication to the other nodes in the group.

Configuring MySQL Group Replication

Setting up MySQL Group Replication involves several steps. First, you need to install MySQL 5.7.17 or higher on all the nodes that will be part of the group. Next, you need to configure each node to use the Group Replication plugin. This involves adding various settings to each node's my.cnf file.

Once the Group Replication plugin is configured, you can start the group. This is done by running the START GROUP_REPLICATION command on one of the nodes. Once the group is running, you can add or remove nodes by running the GROUP_REPLICATION_ADD or GROUP_REPLICATION_REMOVE commands, respectively.

Finally, to monitor the status of the group, you can use the SHOW GROUP_REPLICATION_STATUS command. This command returns information about the state of the group, including the number of nodes in the group, the current master node, and the state of each node.

Conclusion

MySQL Group Replication is a powerful and flexible solution for replicating data in a MySQL environment. With its multi-master features, synchronized replication, high availability and read scalability, it is an excellent choice for workloads high availability read and write.

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