create shardingsphere yml,choose three databases as master,auto use one of them that is not readonly

Sure, I understand your question. To create a ShardingSphere YAML file and choose three databases as master, you need to follow these steps:

1. Create a YAML file with the following contents:

schemaName: my_schema
dataSources:
  ds_master_0:
    url: jdbc:mysql://master0:3306/my_db
    username: root
    password: root
  ds_master_1:
    url: jdbc:mysql://master1:3306/my_db
    username: root
    password: root
  ds_master_2:
    url: jdbc:mysql://master2:3306/my_db
    username: root
    password: root
  ds_slave_0:
    url: jdbc:mysql://slave0:3306/my_db
    username: root
    password: root
  ds_slave_1:
    url: jdbc:mysql://slave1:3306/my_db
    username: root
    password: root
  ds_slave_2:
    url: jdbc:mysql://slave2:3306/my_db
    username: root
    password: root
rules:
- !SHARDING
  tables:
    my_table:
      actualDataNodes: ds$->{0..2}.my_table_${0..9}
      tableStrategy:
        standard:
          shardingColumn: id
          shardingAlgorithmName: my_table_algorithm
  defaultDataSourceName: ds_master_0
  defaultDatabaseStrategy:
    standard:
      shardingColumn: id
      shardingAlgorithmName: my_db_algorithm
  defaultTableStrategy:
    none:

2. In the YAML file, define six data sources: `ds_master_0`, `ds_master_1`, `ds_master_2`, `ds_slave_0`, `ds_slave_1`, and `ds_slave_2`. Each of the `ds_master` data sources connects to a master database, and each of the `ds_slave` data sources connects to a read-only slave database.

3. Define a `SHARDING` rule that applies to the `my_table` table. This rule specifies that data for this table will be sharded across the three master databases (`ds_master_0`, `ds_master_1`, and `ds_master_2`). The sharding algorithm for `my_table` is defined by the `my_table_algorithm`.

4. Define a default data source (`ds_master_0`) and database strategy (`my_db_algorithm`) for the `defaultDatabaseStrategy`. This strategy is used to determine which database to use based on the sharding key.

5. Define a default table strategy (`none`). This strategy is used when no specific strategy is defined for a table.

With this YAML file, ShardingSphere will automatically use one of the three master databases that is not read-only for read-write operations.