Configuring Read/Write Separation

Last updated: 2020-04-03 16:53:01

    Read/Write Separation Based on Read-only Account

    1. Log in to the TDSQL Console. In the instance list, click an instance name or Manage in the "Operation" column to enter the instance management page.
    2. Select the Manage Account tab and click Create.
    3. In the pop-up dialog box, set the account information, set Create as read-only account to Yes, and click Confirm and Go Next.
    4. In the pop-up dialog box, you can set Read-only request allocation policy to define the read policy when a slave failure (or long delay) occurs.
      • Select Master Server to read from the master when the delay of slave exceeds the limit.
      • Select Report Errors to report an error when the delay of the slave exceeds the limit.
      • Select Read Only from Slave Server to ignore the delay parameter and always read from the slave (this is generally used to pull binlogs for sync).
      • Set the Read-only slave server delay parameter to define the data sync delay time, which is to be used together with Master Server and Report Errors under the Read-only request allocation policy.

    Read/Write Separation Based on Comment

    Add the /*slave*/ field before each SQL statement to be "read" by the slave, and add the -c parameter after "mysql" to parse the comment, such as mysql -c -e "/*slave*/sql", to automatically assign "read" requests to the slave. Below are examples:

    //Read from master//
    select * from emp order by sal,deptno desc;
    //Read from slave//
    /*slave*/ select * from emp order by sal,deptno desc
    • This feature only supports read from slave (SELECT) rather than other operations. Non-SELECT statements will fail.
    • The -c parameter needs to be added after mysql to parse the comment.
    • /*slave*/ must be in lowercase, and no spaces are needed before and after the statement.
    • If the MAR (strong sync) mechanism is affected by a slave exception, read from slave will be automatically switched to read from master.

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