An InnoDB Cluster usually runs in a single-primary mode, with one primary instance (read-write) and multiple secondary instances (read-only). Show In order for client applications to handle failover, they need to be aware of the InnoDB cluster topology. They also need to know which instance is the PRIMARY. While it is possible for applications to implement that logic, MySQL Router can provide this functionality for you.
MySQL Router connects to the InnoDB cluster, fetches its metadata and configures itself for use. The generated configuration creates 2 TCP ports: one for read-write sessions (which redirect connections to the PRIMARY) and one for read-only sessions (which redirect connections to one of the SECONDARY instances). Once bootstrapped and configured, start MySQL Router (or set up a service for it to start automatically when the system boots):
You can now connect a MySQL client, such as MySQL Shell to one of the incoming MySQL Router ports and see how the client gets transparently connected to one of the InnoDB cluster instances.
However, when primary node fails, you can just read data and write cannot work. If you want write to work, see High Availability and Multi-Primary cluster for MySql. See this for more detail. This section describes how to use MySQL Router with InnoDB cluster to achieve high availability. Regardless of whether you have deployed a sandbox or production cluster, MySQL Router can configure itself based on the InnoDB cluster's metadata using the Note Do not attempt to configure MySQL Router manually to redirect to the ports of an InnoDB cluster. Always use the The recommended deployment of MySQL Router is on the same host as the application. When using a sandbox deployment, everything is running on a single host, therefore you deploy MySQL Router to the same host. When using a production deployment, we recommend deploying one MySQL Router instance to each machine used to host one of your client applications. It is also possible to deploy MySQL Router to a common machine through which your application instances connect. Assuming
MySQL Router is already installed (see Installing MySQL Router), use the
You are prompted for the instance password and encryption key for MySQL Router to use. This encryption key is used to encrypt the instance password used by MySQL Router to connect to the cluster. The ports you can use to connect to the InnoDB cluster are also displayed. The MySQL
Router bootstrap process creates a
Tip When you change the topology of a cluster by adding another server instance after you have bootstrapped MySQL Router, you need to update
The generated MySQL Router configuration creates TCP ports which you use to connect to the cluster. Ports for communicating with the cluster using both Classic MySQL protocol and X Protocol are created. To use X Protocol the server instances must have X Plugin installed and configured. For a sandbox deployment, instances have X Plugin set up automatically. For a production deployment, if you want to use X Protocol you need to install and configure X Plugin on each instance, see Installing MySQL Shell. The default available TCP ports are:
Depending on your MySQL Router configuration the port numbers might be different to the above. For example if you use the The way incoming connections are redirected depends on the type of cluster being used. When using a single-primary cluster, by default MySQL Router publishes a X Protocol and a classic protocol port, which clients connect to for read-write sessions and which are redirected to the cluster's single primary. With a multi-primary cluster read-write sessions are redirected to one of the primary instances in a round-robin fashion. For example, this means that the
first connection to port 6446 would be redirected to the ic-1 instance, the second connection to port 6446 would be redirected to the ic-2 instance, and so on. For incoming read-only connections MySQL Router redirects connections to one of the secondary instances, also in a round-robin fashion. To modify this behavior see the Once
bootstrapped and configured, start MySQL Router. If you used a system wide install with the
If you installed MySQL Router to a directory using the
To verify which instance you
are actually connected to, simply issue an SQL query against the
Testing High AvailabilityTo test if high availability works, simulate an unexpected halt by killing an instance. The cluster detects the fact that the instance left the cluster and reconfigures itself. Exactly how the cluster reconfigures itself depends on whether you are using a single-primary or multi-primary cluster, and the role the instance serves within the cluster. In single-primary mode:
For more information see Section 18.4.1.1, “Single-Primary Mode”. In multi-primary mode:
For more information see Section 18.4.1.2, “Multi-Primary Mode”. There are
various ways to simulate an instance leaving a cluster, for example you can forcibly stop the MySQL server on an instance, or use the AdminAPI
The cluster detects the change and elects a new primary automatically.
Assuming your session is connected to port 6446, the default read-write classic MySQL protocol port, MySQL Router should detect the change to the cluster's topology and redirect your session to the newly elected primary. To verify this, switch to SQL mode in MySQL Shell using the
In this example, the instance at port 3330 has been elected as the new primary. This shows that the InnoDB cluster provided us with automatic failover, that MySQL Router has automatically reconnected us to the new primary instance, and that we have high availability. MySQL Router and Metadata ServersWhen MySQL Router is bootstrapped against a cluster, it records the server instance's addresses in its configuration file. If any additional instances are added to the cluster after bootstrapping the MySQL Router, they are not automatically detected and therefore are not used for connection routing. To ensure that newly added instances are routed to correctly you must bootstrap MySQL Router against the cluster to read the updated metadata. This means that you must restart MySQL Router and include the Should I bootstrap MySQL router?Do not attempt to configure MySQL Router manually to redirect to the server instances. Always use the --bootstrap option as this ensures that MySQL Router takes its configuration from the metadata.
How do I connect to InnoDB cluster?Create a MySQL InnoDB cluster using MySQL Shell. Configure the MySQL Router using MySQL Shell.. Map Domain Address with IP Address.. Configure MySQL Server to allow remote connections.. Create a MySQL administrator user in and grant privileges.. Configure the group replication using MySQL Shell.. What is MySQL router used for?MySQL Router is lightweight middleware that provides transparent routing between your application and any backend MySQL Servers. It can be used for a wide variety of use cases, such as providing high availability and scalability by effectively routing database traffic to appropriate backend MySQL Servers.
What is MySQL router configuration?The MySQL Router handles routing of clients requests to specific servers while providing additional benefits like load balancing and failover. Router will be managing the direct routing to servers sitting as a worker node in between the server and client ( user application ).
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